Catalyst 2960 Switch Command Reference, Release 12.2(52)SE
Catalyst 2960 Switch Cisco IOS Commands - shutdown through vtp
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shutdown

Table Of Contents

shutdown

shutdown vlan

small-frame violation rate

snmp-server enable traps

snmp-server host

snmp trap mac-notification change

spanning-tree backbonefast

spanning-tree bpdufilter

spanning-tree bpduguard

spanning-tree cost

spanning-tree etherchannel guard misconfig

spanning-tree extend system-id

spanning-tree guard

spanning-tree link-type

spanning-tree loopguard default

spanning-tree mode

spanning-tree mst configuration

spanning-tree mst cost

spanning-tree mst forward-time

spanning-tree mst hello-time

spanning-tree mst max-age

spanning-tree mst max-hops

spanning-tree mst port-priority

spanning-tree mst pre-standard

spanning-tree mst priority

spanning-tree mst root

spanning-tree port-priority

spanning-tree portfast (global configuration)

spanning-tree portfast (interface configuration)

spanning-tree transmit hold-count

spanning-tree uplinkfast

spanning-tree vlan

speed

srr-queue bandwidth limit

srr-queue bandwidth shape

srr-queue bandwidth share

storm-control

switchport access

switchport backup interface

switchport block

switchport host

switchport mode

switchport nonegotiate

switchport port-security

switchport port-security aging

switchport priority extend

switchport protected

switchport trunk

switchport voice vlan

system mtu

test cable-diagnostics tdr

traceroute mac

traceroute mac ip

trust

udld

udld port

udld reset

vlan (global configuration)

vlan (VLAN configuration)

vlan database

vmps reconfirm (privileged EXEC)

vmps reconfirm (global configuration)

vmps retry

vmps server

vtp (global configuration)

vtp (interface configuration)

vtp (VLAN configuration)

vtp primary


shutdown

Use the shutdown interface configuration command to disable an interface. Use the no form of this command to restart a disabled interface.

shutdown

no shutdown

Syntax Description

This command has no arguments or keywords.

Defaults

The port is enabled (not shut down).

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

The shutdown command causes a port to stop forwarding. You can enable the port with the no shutdown command.

The no shutdown command has no effect if the port is a static-access port assigned to a VLAN that has been deleted, suspended, or shut down. The port must first be a member of an active VLAN before it can be re-enabled.

The shutdown command disables all functions on the specified interface.

This command also marks the interface as unavailable. To see if an interface is disabled, use the show interfaces privileged EXEC command. An interface that has been shut down is shown as administratively down in the display.

Examples

These examples show how to disable and re-enable a port:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# shutdown

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# no shutdown

You can verify your settings by entering the show interfaces privileged EXEC command.

Related Commands

Command
Description

show interfaces

Displays the statistical information specific to all interfaces or to a specific interface.


shutdown vlan

Use the shutdown vlan global configuration command to shut down (suspend) local traffic on the specified VLAN. Use the no form of this command to restart local traffic on the VLAN.

shutdown vlan vlan-id

no shutdown vlan vlan-id

Syntax Description

vlan-id

ID of the VLAN to be locally shut down. The range is 2 to 1001. VLANs defined as default VLANs under the VLAN Trunking Protocol (VTP), as well as extended-range VLANs (greater than 1005) cannot be shut down. The default VLANs are 1 and 1002 to 1005.


Defaults

No default is defined.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

The shutdown vlan command does not change the VLAN information in the VTP database. The command shuts down local traffic, but the switch still advertises VTP information.

Examples

This example shows how to shut down traffic on VLAN 2:

Switch(config)# shutdown vlan 2

You can verify your setting by entering the show vlan privileged EXEC command.

Related Commands

Command
Description

shutdown (config-vlan mode)

Shuts down local traffic on the VLAN when in config-VLAN mode (accessed by the vlan vlan-id global configuration command).


small-frame violation rate

Use the small-frame violation rate pps interface configuration command to configure the rate (threshold) for an interface to be error disabled when it receives VLAN-tagged packets that are small frames (67 bytes or less) at the specified rate. Use the no form of this command to return to the default setting.

small-frame violation rate pps

no small-frame violation rate pps

Syntax Description

pps

Specify the threshold at which an interface receiving small frames will be error disabled. The range is 1 to 10,000 packets per second (pps).


Defaults

This feature is disabled.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(44)SE

This command was introduced.


Usage Guidelines

This command enables the rate (threshold) for a port to be error disabled when it receives small frames. Small frames are considered packets that are 67 frames or less.

Use the errdisable detect cause small-frame global configuration command to globally enable the small-frames threshold for each port.

You can configure the port to be automatically re-enabled by using the errdisable recovery cause small-frame global configuration command. You configure the recovery time by using the errdisable recovery interval interval global configuration command.

Examples

This example shows how to enable the small-frame arrival rate feature so that the port is error disabled if incoming small frames arrived at 10,000 pps.

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# small-frame violation rate 10000

You can verify your setting by entering the show interfaces privileged EXEC command.

Related Commands

Command
Description

errdisable detect cause small-frame

Allows any switch port to be put into the error-disabled state if an incoming frame is smaller than the minimum size and arrives at the specified rate (threshold).

errdisable recovery cause small-frame

Enables the recovery timer.

show interfaces

Displays the interface settings on the switch, including input and output flow control.


snmp-server enable traps

Use the snmp-server enable traps global configuration command to enable the switch to send Simple Network Management Protocol (SNMP) notifications for various traps or inform requests to the network management system (NMS). Use the no form of this command to return to the default setting.

snmp-server enable traps [bridge [newroot] [topologychange] | cluster | config | copy-config | cpu threshold | entity | envmon [fan | shutdown | status | supply | temperature] | errdisable [notification-rate value] | flash | ipmulticast | mac-notification [change] [move] [threshold] | msdp | ospf [cisco-specific | errors | lsa | rate-limit | retransmit | state-change] | pim [invalid-pim-message | neighbor-change | rp-mapping-change] | port-security [trap-rate value] | power-ethernet {group name | police} | rtr | snmp [authentication | coldstart | linkdown | linkup | warmstart] | storm-control trap-rate value | stpx [inconsistency] [root-inconsistency] [loop-inconsistency] | syslog | tty | vlan-membership | vlancreate | vlandelete | vtp]

no snmp-server enable traps [bridge [newroot] [topologychange] | cluster | config | copy-config | cpu threshold | entity | envmon [fan | shutdown | status | supply | temperature] | errdisable [notification-rate] | flash | ipmulticast | mac-notification [change] [move] [threshold] | msdp | ospf [cisco-specific | errors | lsa | rate-limit | retransmit | state-change] | pim [invalid-pim-message | neighbor-change | rp-mapping-change] | port-security [trap-rate] | power-ethernet {group name | police} | rtr | snmp [authentication | coldstart | linkdown | linkup | warmstart] | storm-control trap-rate | stpx [inconsistency] [root-inconsistency] [loop-inconsistency] | syslog | tty | vlan-membership | vlancreate | vlandelete | vtp]

Syntax Description

bridge [newroot] [topologychange]

(Optional) Generate STP bridge MIB traps. The keywords have these meanings:

newroot—(Optional) Enable SNMP STP Bridge MIB new root traps.

topologychange—(Optional) Enable SNMP STP Bridge MIB topology change traps.

cluster

(Optional) Enable cluster traps.

config

(Optional) Enable SNMP configuration traps.

copy-config

(Optional) Enable SNMP copy-configuration traps.

cpu threshold

(Optional) Allow CPU-related traps.

This keyword is supported only when the switch is running the LAN Base image.

entity

(Optional) Enable SNMP entity traps.

envmon [fan | shutdown | status | supply | temperature]

Optional) Enable SNMP environmental traps. The keywords have these meanings:

fan—(Optional) Enable fan traps.

shutdown(Optional) Enable environmental monitor shutdown traps.

status—(Optional) Enable SNMP environmental status-change traps.

supply(Optional) Enable environmental monitor power-supply traps.

temperature(Optional) Enable environmental monitor temperature traps.

errdisable [notification-rate value]

(Optional) Enable errdisable traps. Use notification-rate keyword to set the maximum value of errdisable traps sent per minute. The range is 0 to 10000; the default is 0 (no limit imposed; a trap is sent at every occurrence).

flash

(Optional) Enable SNMP FLASH notifications.

ipmulticast

(Optional) Enable IP multicast routing traps.

mac-notification

(Optional) Enable MAC address notification traps.

change

(Optional) Enable MAC address change notification traps.

move

(Optional) Enable MAC address move notification traps.

threshold

(Optional) Enable MAC address table threshold traps.

msdp

(Optional) Enable Multicast Source Discovery Protocol (MSDP) traps.

ospf [cisco-specific | errors | lsa | rate-limit | retransmit | state-change]

(Optional) Enable Open Shortest Path First (OSPF) traps. The keywords have these meanings:

cisco-specific(Optional) Enable Cisco-specific traps.

errors(Optional) Enable error traps.

lsa(Optional) Enable link-state advertisement (LSA) traps.

rate-limit(Optional) Enable rate-limit traps.

retransmit(Optional) Enable packet-retransmit traps.

state-change(Optional) Enable state-change traps.

pim [invalid-pim-message | neighbor-change | rp-mapping-change]

(Optional) Enable Protocol-Independent Multicast (PIM) traps. The keywords have these meanings:

invalid-pim-message(Optional) Enable invalid PIM message traps.

neighbor-change(Optional) Enable PIM neighbor-change traps.

rp-mapping-change(Optional) Enable rendezvous point (RP)-mapping change traps.

port-security
[trap-rate value]

(Optional) Enable port security traps. Use the trap-rate keyword to set the maximum number of port-security traps sent per second. The range is from 0 to 1000; the default is 0 (no limit imposed; a trap is sent at every occurrence).

power-ethernet {group name | police}

(Optional) Enable power-over-Ethernet traps. The keywords have these meanings:

group nameEnable inline power group-based traps for the specified group number or list.

policeEnable inline power policing traps.

rtr

(Optional) Enable SNMP Response Time Reporter traps.

This keyword is supported only when the switch is running the LAN Base image.

snmp [authentication | coldstart | linkdown | linkup | warmstart]

(Optional) Enable SNMP traps. The keywords have these meanings:

authentication(Optional) Enable authentication trap.

coldstart(Optional) Enable cold start trap.

linkdown(Optional) Enable linkdown trap.

linkup(Optional) Enable linkup trap.

warmstart(Optional) Enable warmstart trap.

storm-control trap-rate value

(Optional) Enable storm-control traps. Use the trap-rate keyword to set the maximum number of storm-control traps sent per minute. The range is 0 to 1000; the default is 0 (no limit is imposed; a trap is sent at every occurrence).

stpx

(Optional) Enable SNMP STPX MIB traps. The keywords have these meanings:

inconsistency(Optional) Enable SNMP STPX MIB Inconsistency Update traps.

root-inconsistency(Optional) Enable SNMP STPX MIB Root Inconsistency Update traps.

loop-inconsistency(Optional) Enable SNMP STPX MIB Loop Inconsistency Update traps.

syslog

(Optional) Enable SNMP syslog traps.

tty

(Optional) Send TCP connection traps. This is enabled by default.

vlan-membership

(Optional) Enable SNMP VLAN membership traps.

vlancreate

(Optional) Enable SNMP VLAN-created traps.

vlandelete

(Optional) Enable SNMP VLAN-deleted traps.

vtp

(Optional) Enable VLAN Trunking Protocol (VTP) traps.



Note Though visible in the command-line help strings, the hsrp, insertion, removal, and rtr keywords are not supported. The snmp-server enable informs global configuration command is not supported. To enable the sending of SNMP inform notifications, use the snmp-server enable traps global configuration command combined with the snmp-server host host-addr informs global configuration command.


Defaults

The sending of SNMP traps is disabled.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.

12.2(37)SE

The errdisable notification-rate value keywords were added.

12.2(40)SE

The change, move, and threshold keywords were added to the mac-notification option.

12.2(44)SE

The power-ethernet {group name | police} keywords were added.

12.2(50)SE

The cpu threshold keywords were added.


Usage Guidelines

Specify the host (NMS) that receives the traps by using the snmp-server host global configuration command. If no trap types are specified, all types are sent.

When supported, use the snmp-server enable traps command to enable sending of traps or informs.


Note Informs are not supported in SNMPv1.


To enable more than one type of trap, you must enter a separate snmp-server enable traps command for each trap type.

To set the CPU threshold notification types and values, use the process cpu threshold type global configuration command.

Examples

This example shows how to send VTP traps to the NMS:

Switch(config)# snmp-server enable traps vtp

You can verify your setting by entering the show vtp status or the show running-config privileged EXEC command.

Related Commands

Command
Description

show running-config

Displays the running configuration on the switch. For syntax information, select Cisco IOS Configuration Fundamentals Command Reference, Release 12.2 > File Management Commands > Configuration File Management Commands.

snmp-server host

Specifies the host that receives SNMP traps.


snmp-server host

Use the snmp-server host global configuration command to specify the recipient (host) of a Simple Network Management Protocol (SNMP) notification operation. Use the no form of this command to remove the specified host.

snmp-server host host-addr [informs | traps] [version {1 | 2c | 3 {auth | noauth| priv}] [vrf vrf-instance] {community-string [notification-type]}

no snmp-server host host-addr [informs | traps] [version {1 | 2c | 3 {auth | noauth | priv}] [vrf vrf-instance] community-string

Syntax Description

host-addr

Name or Internet address of the host (the targeted recipient).

udp-port port

(Optional) Configure the User Datagram Protocol (UDP) port number of the host to receive the traps. The range is 0 to 65535.

informs | traps

(Optional) Send SNMP traps or informs to this host.

version 1 | 2c | 3

(Optional) Version of the SNMP used to send the traps.

These keywords are supported:

1—SNMPv1. This option is not available with informs.

2c—SNMPv2C.

3—SNMPv3. These optional keywords can follow the Version 3 keyword:

auth (Optional). Enables Message Digest 5 (MD5) and Secure Hash Algorithm (SHA) packet authentication.

noauth (Default). The noAuthNoPriv security level. This is the default if the [auth | noauth | priv] keyword choice is not specified.

priv (Optional). Enables Data Encryption Standard (DES) packet encryption (also called privacy).

Note The priv keyword is available only when the cryptographic (encrypted) software image is installed.

vrf vrf-instance

(Optional) Virtual private network (VPN) routing instance and name for this host.

community-string

Password-like community string sent with the notification operation. Though you can set this string by using the snmp-server host command, we recommend that you define this string by using the snmp-server community global configuration command before using the snmp-server host command.

Note The @ symbol is used for delimiting the context information. Avoid using the @ symbol as part of the SNMP community string when configuring this command.

notification-type

(Optional) Type of notification to be sent to the host. If no type is specified, all notifications are sent. The notification type can be one or more of the these keywords:

bridgeSend SNMP Spanning Tree Protocol (STP) bridge MIB traps.

clusterSend cluster member status traps.

config—Send SNMP configuration traps.

copy-configSend SNMP copy configuration traps.

cpu threshold—Allow CPU-related traps. This keyword is supported only when the switch is running the LAN Base image.

entity Send SNMP entity traps.

envmonSend environmental monitor traps.

errdisableSend SNMP errdisable notifications.

flashSend SNMP FLASH notifications.

hsrp—Send SNMP Hot Standby Router Protocol (HSRP) traps.

ipmulticast—Send SNMP IP multicast routing traps.

mac-notification—Send SNMP MAC notification traps.

msdp—Send SNMP Multicast Source Discovery Protocol (MSDP) traps.

ospf—Send Open Shortest Path First (OSPF) traps.

pim—Send SNMP Protocol-Independent Multicast (PIM) traps.

port-security—Send SNMP port-security traps.

rtr—Send SNMP Response Time Reporter traps.

snmp—Send SNMP-type traps.

storm-control—Send SNMP storm-control traps.

stpx—Send SNMP STP extended MIB traps.

syslog—Send SNMP syslog traps.

tty—Send TCP connection traps.

udp-port portConfigure the User Datagram Protocol (UDP) port number of the host to receive the traps. The range is from 0 to 65535.

vlan-membership— Send SNMP VLAN membership traps.

vlancreate—Send SNMP VLAN-created traps.

vlandelete—Send SNMP VLAN-deleted traps.

vtp—Send SNMP VLAN Trunking Protocol (VTP) traps.


Defaults

This command is disabled by default. No notifications are sent.

If you enter this command with no keywords, the default is to send all trap types to the host. No informs are sent to this host.

If no version keyword is present, the default is Version 1.

If Version 3 is selected and no authentication keyword is entered, the default is the noauth (noAuthNoPriv) security level.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.

12.2(37)SE

The errdisable notification-rate value keywords were added.

12.2(50)SE

The cpu threshold keywords were added.


Usage Guidelines

SNMP notifications can be sent as traps or inform requests. Traps are unreliable because the receiver does not send acknowledgments when it receives traps. The sender cannot determine if the traps were received. However, an SNMP entity that receives an inform request acknowledges the message with an SNMP response PDU. If the sender never receives the response, the inform request can be sent again. Thus, informs are more likely to reach their intended destinations.

However, informs consume more resources in the agent and in the network. Unlike a trap, which is discarded as soon as it is sent, an inform request must be held in memory until a response is received or the request times out. Traps are also sent only once, but an inform might be retried several times. The retries increase traffic and contribute to a higher overhead on the network.

If you do not enter an snmp-server host command, no notifications are sent. To configure the switch to send SNMP notifications, you must enter at least one snmp-server host command. If you enter the command with no keywords, all trap types are enabled for the host. To enable multiple hosts, you must enter a separate snmp-server host command for each host. You can specify multiple notification types in the command for each host.

If a local user is not associated with a remote host, the switch does not send informs for the auth (authNoPriv) and the priv (authPriv) authentication levels.

When multiple snmp-server host commands are given for the same host and kind of notification (trap or inform), each succeeding command overwrites the previous command. Only the last snmp-server host command is in effect. For example, if you enter an snmp-server host inform command for a host and then enter another snmp-server host inform command for the same host, the second command replaces the first.

The snmp-server host command is used with the snmp-server enable traps global configuration command. Use the snmp-server enable traps command to specify which SNMP notifications are sent globally. For a host to receive most notifications, at least one snmp-server enable traps command and the snmp-server host command for that host must be enabled. Some notification types cannot be controlled with the snmp-server enable traps command. For example, some notification types are always enabled. Other notification types are enabled by a different command.

The no snmp-server host command with no keywords disables traps, but not informs, to the host. To disable informs, use the no snmp-server host informs command.

Examples

This example shows how to configure a unique SNMP community string named comaccess for traps and prevent SNMP polling access with this string through access-list 10:

Switch(config)# snmp-server community comaccess ro 10
Switch(config)# snmp-server host 172.20.2.160 comaccess
Switch(config)# access-list 10 deny any

This example shows how to send the SNMP traps to the host specified by the name myhost.cisco.com. The community string is defined as comaccess:

Switch(config)# snmp-server enable traps
Switch(config)# snmp-server host myhost.cisco.com comaccess snmp 

This example shows how to enable the switch to send all traps to the host myhost.cisco.com by using the community string public:

Switch(config)# snmp-server enable traps
Switch(config)# snmp-server host myhost.cisco.com public

You can verify your settings by entering the show running-config privileged EXEC command.

Related Commands

Command
Description

show running-config

Displays the running configuration on the switch. For syntax information, select Cisco IOS Configuration Fundamentals Command Reference, Release 12.2 > File Management Commands > Configuration File Management Commands.

snmp-server enable traps

Enables SNMP notification for various trap types or inform requests.


snmp trap mac-notification change

Use the snmp trap mac-notification change interface configuration command to enable the Simple Network Management Protocol (SNMP) MAC address change notification trap on a specific Layer 2 interface. Use the no form of this command to return to the default setting.

snmp trap mac-notification change {added | removed}

no snmp trap mac-notification change {added | removed}

Syntax Description

added

Enable the MAC notification trap when a MAC address is added on this interface.

removed

Enable the MAC notification trap when a MAC address is removed from this interface.


Defaults

By default, the traps for both address addition and address removal are disabled.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.

12.2(40)SE

The word change was added to the command.


Usage Guidelines

Even though you enable the notification trap for a specific interface by using the snmp trap mac-notification change command, the trap is generated only when you enter the snmp-server enable traps mac-notification change and the mac address-table notification change global configuration commands.

Examples

This example shows how to enable the MAC notification trap when a MAC address is added to a port:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# snmp trap mac-notification change added

You can verify your settings by entering the show mac address-table notification change interface privileged EXEC command.

Related Commands

Command
Description

clear mac address-table notification

Clears the MAC address notification global counters.

mac address-table notification

Enables the MAC address notification feature.

show mac address-table notification

Displays the MAC address notification settings for all interfaces or on the specified interface when the interface keyword is appended.

snmp-server enable traps

Sends the SNMP MAC notification traps when the mac-notification keyword is appended.


spanning-tree backbonefast

Use the spanning-tree backbonefast global configuration command to enable the BackboneFast feature. Use the no form of the command to return to the default setting.

spanning-tree backbonefast

no spanning-tree backbonefast

Syntax Description

This command has no arguments or keywords.

Defaults

BackboneFast is disabled.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

You can configure the BackboneFast feature for rapid PVST+ or for multiple spanning-tree (MST) mode, but the feature remains disabled (inactive) until you change the spanning-tree mode to PVST+.

BackboneFast starts when a root port or blocked port on a switch receives inferior BPDUs from its designated switch. An inferior BPDU identifies a switch that declares itself as both the root bridge and the designated switch. When a switch receives an inferior BPDU, it means that a link to which the switch is not directly connected (an indirect link) has failed (that is, the designated switch has lost its connection to the root switch. If there are alternate paths to the root switch, BackboneFast causes the maximum aging time on the interfaces on which it received the inferior BPDU to expire and allows a blocked port to move immediately to the listening state. BackboneFast then transitions the interface to the forwarding state. For more information, see the software configuration guide for this release.

Enable BackboneFast on all supported switches to allow the detection of indirect link failures and to start the spanning-tree reconfiguration sooner.

Examples

This example shows how to enable BackboneFast on the switch:

Switch(config)# spanning-tree backbonefast

You can verify your setting by entering the show spanning-tree summary privileged EXEC command.

Related Commands

Command
Description

show spanning-tree summary

Displays a summary of the spanning-tree interface states.


spanning-tree bpdufilter

Use the spanning-tree bpdufilter interface configuration command to prevent an interface from sending or receiving bridge protocol data units (BPDUs). Use the no form of this command to return to the default setting.

spanning-tree bpdufilter {disable | enable}

no spanning-tree bpdufilter

Syntax Description

disable

Disable BPDU filtering on the specified interface.

enable

Enable BPDU filtering on the specified interface.


Defaults

BPDU filtering is disabled.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

You can enable the BPDU filtering feature when the switch is operating in the per-VLAN spanning-tree plus (PVST+), rapid-PVST+, or the multiple spanning-tree (MST) mode.


Caution Enabling BPDU filtering on an interface is the same as disabling spanning tree on it and can result in spanning-tree loops.

You can globally enable BPDU filtering on all Port Fast-enabled interfaces by using the spanning-tree portfast bpdufilter default global configuration command.

You can use the spanning-tree bpdufilter interface configuration command to override the setting of the spanning-tree portfast bpdufilter default global configuration command.

Examples

This example shows how to enable the BPDU filtering feature on a port:

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# spanning-tree bpdufilter enable

You can verify your setting by entering the show running-config privileged EXEC command.

Related Commands

Command
Description

show running-config

Displays the current operating configuration. For syntax information, select Cisco IOS Configuration Fundamentals Command Reference, Release 12.2 > File Management Commands > Configuration File Management Commands.

spanning-tree portfast (global configuration)

Globally enables the BPDU filtering or the BPDU guard feature on Port Fast-enabled interface or enables the Port Fast feature on all nontrunking interfaces.

spanning-tree portfast (interface configuration)

Enables the Port Fast feature on an interface and all its associated VLANs.


spanning-tree bpduguard

Use the spanning-tree bpduguard interface configuration command to put an interface in the error-disabled state when it receives a bridge protocol data unit (BPDU). Use the no form of this command to return to the default setting.

spanning-tree bpduguard {disable | enable}

no spanning-tree bpduguard

Syntax Description

disable

Disable BPDU guard on the specified interface.

enable

Enable BPDU guard on the specified interface.


Defaults

BPDU guard is disabled.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

The BPDU guard feature provides a secure response to invalid configurations because you must manually put the interface back in service. Use the BPDU guard feature in a service-provider network to prevent an interface from being included in the spanning-tree topology.

You can enable the BPDU guard feature when the switch is operating in the per-VLAN spanning-tree plus (PVST+), rapid-PVST+, or the multiple spanning-tree (MST) mode.

You can globally enable BPDU guard on all Port Fast-enabled interfaces by using the spanning-tree portfast bpduguard default global configuration command.

You can use the spanning-tree bpduguard interface configuration command to override the setting of the spanning-tree portfast bpduguard default global configuration command.

Examples

This example shows how to enable the BPDU guard feature on a port:

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# spanning-tree bpduguard enable

You can verify your setting by entering the show running-config privileged EXEC command.

Related Commands

Command
Description

show running-config

Displays the current operating configuration. For syntax information, select Cisco IOS Configuration Fundamentals Command Reference, Release 12.2 > File Management Commands > Configuration File Management Commands.

spanning-tree portfast (global configuration)

Globally enables the BPDU filtering or the BPDU guard feature on Port Fast-enabled interfaces or enables the Port Fast feature on all nontrunking interfaces.

spanning-tree portfast (interface configuration)

Enables the Port Fast feature on an interface and all its associated VLANs.


spanning-tree cost

Use the spanning-tree cost interface configuration command to set the path cost for spanning-tree calculations. If a loop occurs, spanning tree considers the path cost when selecting an interface to place in the forwarding state. Use the no form of this command to return to the default setting.

spanning-tree [vlan vlan-id] cost cost

no spanning-tree [vlan vlan-id] cost

Syntax Description

vlan vlan-id

(Optional) VLAN range associated with a spanning-tree instance. You can specify a single VLAN identified by VLAN ID number, a range of VLANs separated by a hyphen, or a series of VLANs separated by a comma. The range is 1 to 4094.

cost

Path cost. The range is 1 to 200000000, with higher values meaning higher costs.


Defaults

The default path cost is computed from the interface bandwidth setting. These are the IEEE default path cost values:

1000 Mb/s—4

100 Mb/s—19

10 Mb/s—100

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

When you configure the cost, higher values represent higher costs.

If you configure an interface with both the spanning-tree vlan vlan-id cost cost command and the spanning-tree cost cost command, the spanning-tree vlan vlan-id cost cost command takes effect.

Examples

This example shows how to set the path cost to 250 on a port:

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# spanning-tree cost 250

This example shows how to set a path cost to 300 for VLANs 10, 12 to 15, and 20:

Switch(config-if)# spanning-tree vlan 10,12-15,20 cost 300

You can verify your settings by entering the show spanning-tree interface interface-id privileged EXEC command.

Related Commands

Command
Description

show spanning-tree interface interface-id

Displays spanning-tree information for the specified interface.

spanning-tree port-priority

Configures an interface priority.

spanning-tree vlan priority

Sets the switch priority for the specified spanning-tree instance.


spanning-tree etherchannel guard misconfig

Use the spanning-tree etherchannel guard misconfig global configuration command to display an error message when the switch detects an EtherChannel misconfiguration. Use the no form of this command to disable the feature.

spanning-tree etherchannel guard misconfig

no spanning-tree etherchannel guard misconfig

Syntax Description

This command has no arguments or keywords.

Defaults

EtherChannel guard is enabled on the switch.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

When the switch detects an EtherChannel misconfiguration, this error message appears:

PM-4-ERR_DISABLE: Channel-misconfig error detected on [chars], putting [chars] in 
err-disable state.

To show switch ports that are in the misconfigured EtherChannel, use the show interfaces status err-disabled privileged EXEC command. To verify the EtherChannel configuration on a remote device, use the show etherchannel summary privileged EXEC command on the remote device.

When a port is in the error-disabled state because of an EtherChannel misconfiguration, you can bring it out of this state by entering the errdisable recovery cause channel-misconfig global configuration command, or you can manually re-enable it by entering the shutdown and no shut down interface configuration commands.

Examples

This example shows how to enable the EtherChannel guard misconfiguration feature:

Switch(config)# spanning-tree etherchannel guard misconfig

You can verify your settings by entering the show spanning-tree summary privileged EXEC command.

Related Commands

Command
Description

errdisable recovery cause channel-misconfig

Enables the timer to recover from the EtherChannel misconfiguration error-disabled state.

show etherchannel summary

Displays EtherChannel information for a channel as a one-line summary per channel-group.

show interfaces status err-disabled

Displays the interfaces in the error-disabled state.


spanning-tree extend system-id

Use the spanning-tree extend system-id global configuration command to enable the extended system ID feature.

spanning-tree extend system-id


Note Though visible in the command-line help strings, the no version of this command is not supported. You cannot disable the extended system ID feature.


Syntax Description

This command has no arguments or keywords.

Defaults

The extended system ID is enabled.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

The switch supports the IEEE 802.1t spanning-tree extensions. Some of the bits previously used for the switch priority are now used for the extended system ID (VLAN identifier for the per-VLAN spanning-tree plus [PVST+] and rapid PVST+ or as an instance identifier for the multiple spanning tree [MST]).

The spanning tree uses the extended system ID, the switch priority, and the allocated spanning-tree MAC address to make the bridge ID unique for each VLAN or multiple spanning-tree instance.

Support for the extended system ID affects how you manually configure the root switch, the secondary root switch, and the switch priority of a VLAN. For more information, see the "spanning-tree mst root" and the "spanning-tree vlan" sections.

If your network consists of switches that do not support the extended system ID and switches that do support it, it is unlikely that the switch with the extended system ID support will become the root switch. The extended system ID increases the switch priority value every time the VLAN number is greater than the priority of the connected switches.

Related Commands

Command
Description

show spanning-tree summary

Displays a summary of spanning-tree interface states.

spanning-tree mst root

Configures the MST root switch priority and timers based on the network diameter.

spanning-tree vlan priority

Sets the switch priority for the specified spanning-tree instance.


spanning-tree guard

Use the spanning-tree guard interface configuration command to enable root guard or loop guard on all the VLANs associated with the selected interface. Root guard restricts which interface is allowed to be the spanning-tree root port or the path-to-the root for the switch. Loop guard prevents alternate or root ports from becoming designated ports when a failure creates a unidirectional link. Use the no form of this command to return to the default setting.

spanning-tree guard {loop | none | root}

no spanning-tree guard

Syntax Description

loop

Enable loop guard.

none

Disable root guard or loop guard.

root

Enable root guard.


Defaults

Root guard is disabled.

Loop guard is configured according to the spanning-tree loopguard default global configuration command (globally disabled).

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

You can enable root guard or loop guard when the switch is operating in the per-VLAN spanning-tree plus (PVST+), rapid-PVST+, or the multiple spanning-tree (MST) mode.

When root guard is enabled, if spanning-tree calculations cause an interface to be selected as the root port, the interface transitions to the root-inconsistent (blocked) state to prevent the customer's switch from becoming the root switch or being in the path to the root. The root port provides the best path from the switch to the root switch.

When the no spanning-tree guard or the no spanning-tree guard none command is entered, root guard is disabled for all VLANs on the selected interface. If this interface is in the root-inconsistent (blocked) state, it automatically transitions to the listening state.

Do not enable root guard on interfaces that will be used by the UplinkFast feature. With UplinkFast, the backup interfaces (in the blocked state) replace the root port in the case of a failure. However, if root guard is also enabled, all the backup interfaces used by the UplinkFast feature are placed in the root-inconsistent state (blocked) and prevented from reaching the forwarding state. The UplinkFast feature is not available when the switch is operating in the rapid-PVST+ or MST mode.

Loop guard is most effective when it is configured on the entire switched network. When the switch is operating in PVST+ or rapid-PVST+ mode, loop guard prevents alternate and root ports from becoming designated ports, and spanning tree does not send bridge protocol data units (BPDUs) on root or alternate ports. When the switch is operating in MST mode, BPDUs are not sent on nonboundary interfaces if the interface is blocked by loop guard in all MST instances. On a boundary interface, loop guard blocks the interface in all MST instances.

To disable root guard or loop guard, use the spanning-tree guard none interface configuration command. You cannot enable both root guard and loop guard at the same time.

You can override the setting of the spanning-tree loopguard default global configuration command by using the spanning-tree guard loop interface configuration command.

Examples

This example shows how to enable root guard on all the VLANs associated with the specified port:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# spanning-tree guard root

This example shows how to enable loop guard on all the VLANs associated with the specified port:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# spanning-tree guard loop

You can verify your settings by entering the show running-config privileged EXEC command.

Related Commands

Command
Description

show running-config

Displays the current operating configuration. For syntax information, select Cisco IOS Configuration Fundamentals Command Reference, Release 12.2 > File Management Commands > Configuration File Management Commands.

spanning-tree cost

Sets the path cost for spanning-tree calculations.

spanning-tree loopguard default

Prevents alternate or root ports from becoming designated ports because of a failure that leads to a unidirectional link.

spanning-tree mst cost

Configures the path cost for MST calculations.

spanning-tree mst port-priority

Configures an interface priority.

spanning-tree mst root

Configures the MST root switch priority and timers based on the network diameter.

spanning-tree port-priority

Configures an interface priority.

spanning-tree vlan priority

Sets the switch priority for the specified spanning-tree instance.


spanning-tree link-type

Use the spanning-tree link-type interface configuration command to override the default link-type setting, which is determined by the duplex mode of the interface, and to enable rapid spanning-tree transitions to the forwarding state. Use the no form of this command to return to the default setting.

spanning-tree link-type {point-to-point | shared}

no spanning-tree link-type

Syntax Description

point-to-point

Specify that the link type of an interface is point-to-point.

shared

Specify that the link type of an interface is shared.


Defaults

The switch derives the link type of an interface from the duplex mode. A full-duplex interface is considered a point-to-point link, and a half-duplex interface is considered a shared link.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

You can override the default setting of the link type by using the spanning-tree link-type command. For example, a half-duplex link can be physically connected point-to-point to a single interface on a remote switch running the Multiple Spanning Tree Protocol (MSTP) or the rapid per-VLAN spanning-tree plus (rapid-PVST+) protocol and be enabled for rapid transitions.

Examples

This example shows how to specify the link type as shared (regardless of the duplex setting) and to prevent rapid transitions to the forwarding state:

Switch(config-if)# spanning-tree link-type shared

You can verify your setting by entering the show spanning-tree mst interface interface-id or the show spanning-tree interface interface-id privileged EXEC command.

Related Commands

Command
Description

clear spanning-tree detected-protocols

Restarts the protocol migration process (force the renegotiation with neighboring switches) on all interfaces or on the specified interface.

show spanning-tree interface interface-id

Displays spanning-tree state information for the specified interface.

show spanning-tree mst interface interface-id

Displays MST information for the specified interface.


spanning-tree loopguard default

Use the spanning-tree loopguard default global configuration command to prevent alternate or root ports from becoming designated ports because of a failure that leads to a unidirectional link. Use the no form of this command to return to the default setting.

spanning-tree loopguard default

no spanning-tree loopguard default

Syntax Description

This command has no arguments or keywords.

Defaults

Loop guard is disabled.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

You can enable the loop guard feature when the switch is operating in the per-VLAN spanning-tree plus (PVST+), rapid-PVST+, or the multiple spanning-tree (MST) mode.

Loop guard is most effective when it is configured on the entire switched network. When the switch is operating in PVST+ or rapid-PVST+ mode, loop guard prevents alternate and root ports from becoming designated ports, and spanning tree does not send bridge protocol data units (BPDUs) on root or alternate ports. When the switch is operating in MST mode, BPDUs are not sent on nonboundary interfaces if the interface is blocked by loop guard in all MST instances. On a boundary interface, loop guard blocks the interface in all MST instances.

Loop guard operates only on interfaces that the spanning tree identifies as point-to-point.

You can override the setting of the spanning-tree loopguard default global configuration command by using the spanning-tree guard loop interface configuration command.

Examples

This example shows how to globally enable loop guard:

Switch(config)# spanning-tree loopguard default

You can verify your settings by entering the show running-config privileged EXEC command.

Related Commands

Command
Description

show running-config

Displays the current operating configuration. For syntax information, select Cisco IOS Configuration Fundamentals Command Reference, Release 12.2 > File Management Commands > Configuration File Management Commands.

spanning-tree guard loop

Enables the loop guard feature on all the VLANs associated with the specified interface.


spanning-tree mode

Use the spanning-tree mode global configuration command to enable per-VLAN spanning-tree plus (PVST+), rapid PVST+, or multiple spanning tree (MST) on your switch. Use the no form of this command to return to the default setting.

spanning-tree mode {mst | pvst | rapid-pvst}

no spanning-tree mode

Syntax Description

mst

Enable MST and Rapid Spanning Tree Protocol (RSTP) (based on IEEE 802.1s and IEEE 802.1w).

pvst

Enable PVST+ (based on IEEE 802.1D).

rapid-pvst

Enable rapid PVST+ (based on IEEE 802.1w).


Defaults

The default mode is PVST+.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

The switch supports PVST+, rapid PVST+, and MSTP, but only one version can be active at any time: All VLANs run PVST+, all VLANs run rapid PVST+, or all VLANs run MSTP.

When you enable the MST mode, RSTP is automatically enabled.


Caution Changing spanning-tree modes can disrupt traffic because all spanning-tree instances are stopped for the previous mode and restarted in the new mode.

Examples

This example shows to enable MST and RSTP on the switch:

Switch(config)# spanning-tree mode mst

This example shows to enable rapid PVST+ on the switch:

Switch(config)# spanning-tree mode rapid-pvst

You can verify your setting by entering the show running-config privileged EXEC command.

Related Commands

Command
Description

show running-config

Displays the current operating configuration. For syntax information, select Cisco IOS Configuration Fundamentals Command Reference, Release 12.2 > File Management Commands > Configuration File Management Commands.


spanning-tree mst configuration

Use the spanning-tree mst configuration global configuration command to enter multiple spanning-tree (MST) configuration mode through which you configure the MST region. Use the no form of this command to return to the default settings.

spanning-tree mst configuration

no spanning-tree mst configuration

Syntax Description

This command has no arguments or keywords.

Defaults

The default mapping is that all VLANs are mapped to the common and internal spanning-tree (CIST) instance (instance 0).

The default name is an empty string.

The revision number is 0.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.

12.2(25)SED

The instance-id range changed to 1 to 4094.


Usage Guidelines

The spanning-tree mst configuration command enables the MST configuration mode. These configuration commands are available:

abort: exits the MST region configuration mode without applying configuration changes.

exit: exits the MST region configuration mode and applies all configuration changes.

instance instance-id vlan vlan-range: maps VLANs to an MST instance. The range for the instance-id is 1 to 4094. The range for vlan-range is 1 to 4094. You can specify a single VLAN identified by VLAN ID number, a range of VLANs separated by a hyphen, or a series of VLANs separated by a comma.

name name: sets the configuration name. The name string has a maximum length of 32 characters and is case sensitive.

no: negates the instance, name, and revision commands or sets them to their defaults.

private-vlan: Though visible in the command-line help strings, this command is not supported.

revision version: sets the configuration revision number. The range is 0 to 65535.

show [current | pending]: displays the current or pending MST region configuration.

In MST mode, the switch supports up to 65 MST instances. The number of VLANs that can be mapped to a particular MST instance is unlimited.

When you map VLANs to an MST instance, the mapping is incremental, and VLANs specified in the command are added to or removed from the VLANs that were previously mapped. To specify a range, use a hyphen; for example, instance 1 vlan 1-63 maps VLANs 1 to 63 to MST instance 1. To specify a series, use a comma; for example, instance 1 vlan 10, 20, 30 maps VLANs 10, 20, and 30 to MST instance 1.

All VLANs that are not explicitly mapped to an MST instance are mapped to the common and internal spanning tree (CIST) instance (instance 0) and cannot be unmapped from the CIST by using the no form of the command.

For two or more switches to be in the same MST region, they must have the same VLAN mapping, the same configuration revision number, and the same name.

Examples

This example shows how to enter MST configuration mode, map VLANs 10 to 20 to MST instance 1, name the region region1, set the configuration revision to 1, display the pending configuration, apply the changes, and return to global configuration mode:

Switch# spanning-tree mst configuration
Switch(config-mst)# instance 1 vlan 10-20
Switch(config-mst)# name region1
Switch(config-mst)# revision 1
Switch(config-mst)# show pending
Pending MST configuration
Name      [region1]
Revision  1
Instance  Vlans Mapped
--------  ---------------------
0         1-9,21-4094
1         10-20
-------------------------------

Switch(config-mst)# exit
Switch(config)#

This example shows how to add VLANs 1 to 100 to the ones already mapped (if any) to instance 2, to move VLANs 40 to 60 that were previously mapped to instance 2 to the CIST instance, to add VLAN 10 to instance 10, and to remove all the VLANs mapped to instance 2 and map them to the CIST instance:

Switch(config-mst)# instance 2 vlan 1-100
Switch(config-mst)# no instance 2 vlan 40-60
Switch(config-mst)# instance 10 vlan 10
Switch(config-mst)# no instance 2

You can verify your settings by entering the show pending MST configuration command.

Related Commands

Command
Description

show spanning-tree mst configuration

Displays the MST region configuration.


spanning-tree mst cost

Use the spanning-tree mst cost interface configuration command to set the path cost for multiple spanning-tree (MST) calculations. If a loop occurs, spanning tree considers the path cost when selecting an interface to put in the forwarding state. Use the no form of this command to return to the default setting.

spanning-tree mst instance-id cost cost

no spanning-tree mst instance-id cost

Syntax Description

instance-id

Range of spanning-tree instances. You can specify a single instance, a range of instances separated by a hyphen, or a series of instances separated by a comma. The range is 0 to 4094.

cost

Path cost is 1 to 200000000, with higher values meaning higher costs.


Defaults

The default path cost is computed from the interface bandwidth setting. These are the IEEE default path cost values:

1000 Mb/s—20000

100 Mb/s—200000

10 Mb/s—2000000

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.

12.2(25)SED

The instance-id range changed to1 to 4094.


Usage Guidelines

When you configure the cost, higher values represent higher costs.

Examples

This example shows how to set a path cost of 250 on a port associated with instances 2 and 4:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# spanning-tree mst 2,4 cost 250

You can verify your settings by entering the show spanning-tree mst interface interface-id privileged EXEC command.

Related Commands

Command
Description

show spanning-tree mst interface interface-id

Displays MST information for the specified interface.

spanning-tree mst port-priority

Configures an interface priority.

spanning-tree mst priority

Configures the switch priority for the specified spanning-tree instance.


spanning-tree mst forward-time

Use the spanning-tree mst forward-time global configuration command to set the forward-delay time for all multiple spanning-tree (MST) instances. The forwarding time specifies how long each of the listening and learning states last before the interface begins forwarding. Use the no form of this command to return to the default setting.

spanning-tree mst forward-time seconds

no spanning-tree mst forward-time

Syntax Description

seconds

Length of the listening and learning states. The range is 4 to 30 seconds.


Defaults

The default is 15 seconds.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

Changing the spanning-tree mst forward-time command affects all spanning-tree instances.

Examples

This example shows how to set the spanning-tree forwarding time to 18 seconds for all MST instances:

Switch(config)# spanning-tree mst forward-time 18

You can verify your setting by entering the show spanning-tree mst privileged EXEC command.

Related Commands

Command
Description

show spanning-tree mst

Displays MST information.

spanning-tree mst hello-time

Sets the interval between hello bridge protocol data units (BPDUs) sent by root switch configuration messages.

spanning-tree mst max-age

Sets the interval between messages that the spanning tree receives from the root switch.

spanning-tree mst max-hops

Sets the number of hops in a region before the BPDU is discarded.


spanning-tree mst hello-time

Use the spanning-tree mst hello-time global configuration command to set the interval between hello bridge protocol data units (BPDUs) sent by root switch configuration messages. Use the no form of this command to return to the default setting.

spanning-tree mst hello-time seconds

no spanning-tree mst hello-time

Syntax Description

seconds

Interval between hello BPDUs sent by root switch configuration messages. The range is 1 to 10 seconds.


Defaults

The default is 2 seconds.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

After you set the spanning-tree mst max-age seconds global configuration command, if a switch does not receive BPDUs from the root switch within the specified interval, the switch recomputes the spanning-tree topology. The max-age setting must be greater than the hello-time setting.

Changing the spanning-tree mst hello-time command affects all spanning-tree instances.

Examples

This example shows how to set the spanning-tree hello time to 3 seconds for all multiple spanning-tree (MST) instances:

Switch(config)# spanning-tree mst hello-time 3

You can verify your setting by entering the show spanning-tree mst privileged EXEC command.

Related Commands

Command
Description

show spanning-tree mst

Displays MST information.

spanning-tree mst forward-time

Sets the forward-delay time for all MST instances.

spanning-tree mst max-age

Sets the interval between messages that the spanning tree receives from the root switch.

spanning-tree mst max-hops

Sets the number of hops in a region before the BPDU is discarded.


spanning-tree mst max-age

Use the spanning-tree mst max-age global configuration command to set the interval between messages that the spanning tree receives from the root switch. If a switch does not receive a bridge protocol data unit (BPDU) message from the root switch within this interval, it recomputes the spanning-tree topology. Use the no form of this command to return to the default setting.

spanning-tree mst max-age seconds

no spanning-tree mst max-age

Syntax Description

seconds

Interval between messages the spanning tree receives from the root switch. The range is 6 to 40 seconds.


Defaults

The default is 20 seconds.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

After you set the spanning-tree mst max-age seconds global configuration command, if a switch does not receive BPDUs from the root switch within the specified interval, the switch recomputes the spanning-tree topology. The max-age setting must be greater than the hello-time setting.

Changing the spanning-tree mst max-age command affects all spanning-tree instances.

Examples

This example shows how to set the spanning-tree max-age to 30 seconds for all multiple spanning-tree (MST) instances:

Switch(config)# spanning-tree mst max-age 30

You can verify your setting by entering the show spanning-tree mst privileged EXEC command.

Related Commands

Command
Description

show spanning-tree mst

Displays MST information.

spanning-tree mst forward-time

Sets the forward-delay time for all MST instances.

spanning-tree mst hello-time

Sets the interval between hello BPDUs sent by root switch configuration messages.

spanning-tree mst max-hops

Sets the number of hops in a region before the BPDU is discarded.


spanning-tree mst max-hops

Use the spanning-tree mst max-hops global configuration command to set the number of hops in a region before the bridge protocol data unit (BPDU) is discarded and the information held for an interface is aged. Use the no form of this command to return to the default setting.

spanning-tree mst max-hops hop-count

no spanning-tree mst max-hops

Syntax Description

hop-count

Number of hops in a region before the BPDU is discarded. The range is 1 to 255 hops.


Defaults

The default is 20 hops.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.

12.2(25)SED

The hop-count range changed to 1 to 255.


Usage Guidelines

The root switch of the instance always sends a BPDU (or M-record) with a cost of 0 and the hop count set to the maximum value. When a switch receives this BPDU, it decrements the received remaining hop count by one and propagates the decremented count as the remaining hop count in the generated M-records. A switch discards the BPDU and ages the information held for the interface when the count reaches 0.

Changing the spanning-tree mst max-hops command affects all spanning-tree instances.

Examples

This example shows how to set the spanning-tree max-hops to 10 for all multiple spanning-tree (MST) instances:

Switch(config)# spanning-tree mst max-hops 10

You can verify your setting by entering the show spanning-tree mst privileged EXEC command.

Related Commands

Command
Description

show spanning-tree mst

Displays MST information.

spanning-tree mst forward-time

Sets the forward-delay time for all MST instances.

spanning-tree mst hello-time

Sets the interval between hello BPDUs sent by root switch configuration messages.

spanning-tree mst max-age

Sets the interval between messages that the spanning tree receives from the root switch.


spanning-tree mst port-priority

Use the spanning-tree mst port-priority interface configuration command to configure an interface priority. If a loop occurs, the Multiple Spanning Tree Protocol (MSTP) can find the interface to put in the forwarding state. Use the no form of this command to return to the default setting.

spanning-tree mst instance-id port-priority priority

no spanning-tree mst instance-id port-priority

Syntax Description

instance-id

Range of spanning-tree instances. You can specify a single instance, a range of instances separated by a hyphen, or a series of instances separated by a comma. The range is 0 to 4094.

priority

The range is 0 to 240 in increments of 16. Valid priority values are 0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, and 240. All other values are rejected. The lower the number, the higher the priority.


Defaults

The default is 128.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.

12.2(25)SED

The instance-id range changed to 1 to 4094.


Usage Guidelines

You can assign higher priority values (lower numerical values) to interfaces that you want selected first and lower priority values (higher numerical values) that you want selected last. If all interfaces have the same priority value, the multiple spanning tree (MST) puts the interface with the lowest interface number in the forwarding state and blocks other interfaces.

Examples

This example shows how to increase the likelihood that the interface associated with spanning-tree instances 20 and 22 is placed into the forwarding state if a loop occurs:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# spanning-tree mst 20,22 port-priority 0

You can verify your settings by entering the show spanning-tree mst interface interface-id privileged EXEC command.

Related Commands

Command
Description

show spanning-tree mst interface interface-id

Displays MST information for the specified interface.

spanning-tree mst cost

Sets the path cost for MST calculations.

spanning-tree mst priority

Sets the switch priority for the specified spanning-tree instance.


spanning-tree mst pre-standard

Use the spanning-tree mst pre-standard interface configuration command to configure a port to send only prestandard bridge protocol data units (BPDUs).

spanning-tree mst pre-standard

no spanning-tree mst pre-standard

Syntax Description

This command has no arguments or keywords.

Command Default

The default state is automatic detection of prestandard neighbors.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)SED

This command was introduced.


Usage Guidelines

The port can accept both prestandard and standard BPDUs. If the neighbor types are mismatched, only the common and internal spanning tree (CIST) runs on this interface.


Note If a switch port is connected to a switch running prestandard Cisco IOS software, you must use the spanning-tree mst pre-standard interface configuration command on the port. If you do not configure the port to send only prestandard BPDUs, the Multiple STP (MSTP) performance might diminish.


When the port is configured to automatically detect prestandard neighbors, the prestandard flag always appears in the show spanning-tree mst commands.

Examples

This example shows how to configure a port to send only prestandard BPDUs:

Switch(config-if)# spanning-tree mst pre-standard

You can verify your settings by entering the show spanning-tree mst privileged EXEC command.

Related Commands

Command
Description

show spanning-tree mst instance-id

Displays multiple spanning-tree (MST) information, including the prestandard flag, for the specified interface.


spanning-tree mst priority

Use the spanning-tree mst priority global configuration command to set the switch priority for the specified spanning-tree instance. Use the no form of this command to return to the default setting.

spanning-tree mst instance-id priority priority

no spanning-tree mst instance-id priority

Syntax Description

instance-id

Range of spanning-tree instances. You can specify a single instance, a range of instances separated by a hyphen, or a series of instances separated by a comma. The range is 0 to 4094.

priority

Set the switch priority for the specified spanning-tree instance. This setting affects the likelihood that the switch is selected as the root switch. A lower value increases the probability that the switch is selected as the root switch.

The range is 0 to 61440 in increments of 4096. Valid priority values are 0, 4096, 8192, 12288, 16384, 20480, 24576, 28672, 32768, 36864, 40960, 45056, 49152, 53248, 57344, and 61440. All other values are rejected.


Defaults

The default is 32768.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.

12.2(25)SED

The instance-id range changed to 1 to 4094.


Examples

This example shows how to set the spanning-tree priority to 8192 for multiple spanning-tree instances (MST) 20 to 21:

Switch(config)# spanning-tree mst 20-21 priority 8192

You can verify your settings by entering the show spanning-tree mst instance-id privileged EXEC command.

Related Commands

Command
Description

show spanning-tree mst instance-id

Displays MST information for the specified interface.

spanning-tree mst cost

Sets the path cost for MST calculations.

spanning-tree mst port-priority

Configures an interface priority.


spanning-tree mst root

Use the spanning-tree mst root global configuration command to configure the multiple spanning-tree (MST) root switch priority and timers based on the network diameter. Use the no form of this command to return to the default settings.

spanning-tree mst instance-id root {primary | secondary} [diameter net-diameter
[hello-time seconds]]

no spanning-tree mst instance-id root

Syntax Description

instance-id

Range of spanning-tree instances. You can specify a single instance, a range of instances separated by a hyphen, or a series of instances separated by a comma. The range is 0 to 4094.

root primary

Force this switch to be the root switch.

root secondary

Set this switch to be the root switch should the primary root switch fail.

diameter net-diameter

(Optional) Set the maximum number of switches between any two end stations. The range is 2 to 7. This keyword is available only for MST instance 0.

hello-time seconds

(Optional) Set the interval between hello bridge protocol data units (BPDUs) sent by the root switch configuration messages. The range is 1 to 10 seconds. This keyword is available only for MST instance 0.


Defaults

The primary root switch priority is 24576.

The secondary root switch priority is 28672.

The hello time is 2 seconds.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.

12.2(25)SED

The instance-id range changed to1 to 4094.


Usage Guidelines

Use the spanning-tree mst instance-id root command only on backbone switches.

When you enter the spanning-tree mst instance-id root command, the software tries to set a high enough priority to make this switch the root of the spanning-tree instance. Because of the extended system ID support, the switch sets the switch priority for the instance to 24576 if this value will cause this switch to become the root for the specified instance. If any root switch for the specified instance has a switch priority lower than 24576, the switch sets its own priority to 4096 less than the lowest switch priority. (4096 is the value of the least-significant bit of a 4-bit switch priority value.)

When you enter the spanning-tree mst instance-id root secondary command, because of support for the extended system ID, the software changes the switch priority from the default value (32768) to 28672. If the root switch fails, this switch becomes the next root switch (if the other switches in the network use the default switch priority of 32768 and are therefore unlikely to become the root switch).

Examples

This example shows how to configure the switch as the root switch for instance 10 with a network diameter of 4:

Switch(config)# spanning-tree mst 10 root primary diameter 4

This example shows how to configure the switch as the secondary root switch for instance 10 with a network diameter of 4:

Switch(config)# spanning-tree mst 10 root secondary diameter 4 

You can verify your settings by entering the show spanning-tree mst instance-id privileged EXEC command.

Related Commands

Command
Description

show spanning-tree mst instance-id

Displays MST information for the specified instance.

spanning-tree mst forward-time

Sets the forward-delay time for all MST instances.

spanning-tree mst hello-time

Sets the interval between hello BPDUs sent by root switch configuration messages.

spanning-tree mst max-age

Sets the interval between messages that the spanning tree receives from the root switch.

spanning-tree mst max-hops

Sets the number of hops in a region before the BPDU is discarded.


spanning-tree port-priority

Use the spanning-tree port-priority interface configuration command to configure an interface priority. If a loop occurs, spanning tree can find the interface to put in the forwarding state. Use the no form of this command to return to the default setting.

spanning-tree [vlan vlan-id] port-priority priority

no spanning-tree [vlan vlan-id] port-priority

Syntax Description

vlan vlan-id

(Optional) VLAN range associated with a spanning-tree instance. You can specify a single VLAN identified by VLAN ID number, a range of VLANs separated by a hyphen, or a series of VLANs separated by a comma. The range is 1 to 4094.

priority

Number from 0 to 240, in increments of 16. Valid values are 0, 16, 32, 48, 64, 80, 96, 112, 128, 144, 160, 176, 192, 208, 224, and 240. All other values are rejected. The lower the number, the higher the priority.


Defaults

The default is 128.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

If the variable vlan-id is omitted, the command applies to the spanning-tree instance associated with VLAN 1.

You can set the priority on a VLAN that has no interfaces assigned to it. The setting takes effect when you assign the interface to the VLAN.

If you configure an interface with both the spanning-tree vlan vlan-id port-priority priority command and the spanning-tree port-priority priority command, the spanning-tree vlan vlan-id port-priority priority command takes effect.

Examples

This example shows how to increase the likelihood that a port will be put in the forwarding state if a loop occurs:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# spanning-tree vlan 20 port-priority 0

This example shows how to set the port-priority value on VLANs 20 to 25:

Switch(config-if)# spanning-tree vlan 20-25 port-priority 0

You can verify your settings by entering the show spanning-tree interface interface-id privileged EXEC command.

Related Commands

Command
Description

show spanning-tree interface interface-id

Displays spanning-tree information for the specified interface.

spanning-tree cost

Sets the path cost for spanning-tree calculations.

spanning-tree vlan priority

Sets the switch priority for the specified spanning-tree instance.


spanning-tree portfast (global configuration)

Use the spanning-tree portfast global configuration command to globally enable bridge protocol data unit (BPDU) filtering on Port Fast-enabled interfaces, the BPDU guard feature on Port Fast-enabled interfaces, or the Port Fast feature on all nontrunking interfaces. The BPDU filtering feature prevents the switch interface from sending or receiving BPDUs. The BPDU guard feature puts Port Fast-enabled interfaces that receive BPDUs in an error-disabled state. Use the no form of this command to return to the default settings.

spanning-tree portfast {bpdufilter default | bpduguard default | default}

no spanning-tree portfast {bpdufilter default | bpduguard default | default}

Syntax Description

bpdufilter default

Globally enable BPDU filtering on Port Fast-enabled interfaces and prevent the switch interface connected to end stations from sending or receiving BPDUs.

bpduguard default

Globally enable the BPDU guard feature on Port Fast-enabled interfaces and place the interfaces that receive BPDUs in an error-disabled state.

default

Globally enable the Port Fast feature on all nontrunking interfaces. When the Port Fast feature is enabled, the interface changes directly from a blocking state to a forwarding state without making the intermediate spanning-tree state changes.


Defaults

The BPDU filtering, the BPDU guard, and the Port Fast features are disabled on all interfaces unless they are individually configured.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

You can enable these features when the switch is operating in the per-VLAN spanning-tree plus (PVST+) rapid-PVST+, or the multiple spanning-tree (MST) mode.

Use the spanning-tree portfast bpdufilter default global configuration command to globally enable BPDU filtering on interfaces that are Port Fast-enabled (the interfaces are in a Port Fast-operational state). The interfaces still send a few BPDUs at link-up before the switch begins to filter outbound BPDUs. You should globally enable BPDU filtering on a switch so that hosts connected to switch interfaces do not receive BPDUs. If a BPDU is received on a Port Fast-enabled interface, the interface loses its Port Fast-operational status and BPDU filtering is disabled.

You can override the spanning-tree portfast bpdufilter default global configuration command by using the spanning-tree bdpufilter interface configuration command.


Caution Enabling BPDU filtering on an interface is the same as disabling spanning tree on it and can result in spanning-tree loops.

Use the spanning-tree portfast bpduguard default global configuration command to globally enable BPDU guard on interfaces that are in a Port Fast-operational state. In a valid configuration, Port Fast-enabled interfaces do not receive BPDUs. Receiving a BPDU on a Port Fast-enabled interface signals an invalid configuration, such as the connection of an unauthorized device, and the BPDU guard feature puts the interface in the error-disabled state. The BPDU guard feature provides a secure response to invalid configurations because you must manually put the interface back in service. Use the BPDU guard feature in a service-provider network to prevent an access port from participating in the spanning tree.

You can override the spanning-tree portfast bpduguard default global configuration command by using the spanning-tree bdpuguard interface configuration command.

Use the spanning-tree portfast default global configuration command to globally enable the Port Fast feature on all nontrunking interfaces. Configure Port Fast only on interfaces that connect to end stations; otherwise, an accidental topology loop could cause a data packet loop and disrupt switch and network operation. A Port Fast-enabled interface moves directly to the spanning-tree forwarding state when linkup occurs without waiting for the standard forward-delay time.

You can override the spanning-tree portfast default global configuration command by using the spanning-tree portfast interface configuration command. You can use the no spanning-tree portfast default global configuration command to disable Port Fast on all interfaces unless they are individually configured with the spanning-tree portfast interface configuration command.

Examples

This example shows how to globally enable the BPDU filtering feature:

Switch(config)# spanning-tree portfast bpdufilter default

This example shows how to globally enable the BPDU guard feature:

Switch(config)# spanning-tree portfast bpduguard default

This example shows how to globally enable the Port Fast feature on all nontrunking interfaces:

Switch(config)# spanning-tree portfast default

You can verify your settings by entering the show running-config privileged EXEC command.

Related Commands

Command
Description

show running-config

Displays the current operating configuration. For syntax information, select Cisco IOS Configuration Fundamentals Command Reference, Release 12.2 > File Management Commands > Configuration File Management Commands.

spanning-tree bpdufilter

Prevents an interface from sending or receiving BPDUs.

spanning-tree bpduguard

Puts an interface in the error-disabled state when it receives a BPDU.

spanning-tree portfast (interface configuration)

Enables the Port Fast feature on an interface in all its associated VLANs.


spanning-tree portfast (interface configuration)

Use the spanning-tree portfast interface configuration command to enable the Port Fast feature on an interface in all its associated VLANs. When the Port Fast feature is enabled, the interface changes directly from a blocking state to a forwarding state without making the intermediate spanning-tree state changes. Use the no form of this command to return to the default setting.

spanning-tree portfast [disable | trunk]

no spanning-tree portfast

Syntax Description

disable

(Optional) Disable the Port Fast feature on the specified interface.

trunk

(Optional) Enable the Port Fast feature on a trunking interface.


Defaults

The Port Fast feature is disabled on all interfaces; however, it is automatically enabled on dynamic-access ports.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

Use this feature only on interfaces that connect to end stations; otherwise, an accidental topology loop could cause a data packet loop and disrupt switch and network operation.

To enable Port Fast on trunk ports, you must use the spanning-tree portfast trunk interface configuration command. The spanning-tree portfast command is not supported on trunk ports.

You can enable this feature when the switch is operating in the per-VLAN spanning-tree plus (PVST+), rapid-PVST+, or the multiple spanning-tree (MST) mode.

This feature affects all VLANs on the interface.

An interface with the Port Fast feature enabled is moved directly to the spanning-tree forwarding state without the standard forward-time delay.

You can use the spanning-tree portfast default global configuration command to globally enable the Port Fast feature on all nontrunking interfaces. However, the spanning-tree portfast interface configuration command can override the global setting.

If you configure the spanning-tree portfast default global configuration command, you can disable Port Fast on an interface that is not a trunk interface by using the spanning-tree portfast disable interface configuration command.

Examples

This example shows how to enable the Port Fast feature on a port:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# spanning-tree portfast

You can verify your settings by entering the show running-config privileged EXEC command.

Related Commands

Command
Description

show running-config

Displays the current operating configuration. For syntax information, select Cisco IOS Configuration Fundamentals Command Reference, Release 12.2 > File Management Commands > Configuration File Management Commands.

spanning-tree bpdufilter

Prevents an interface from sending or receiving bridge protocol data units (BPDUs).

spanning-tree bpduguard

Puts an interface in the error-disabled state when it receives a BPDU.

spanning-tree portfast (global configuration)

Globally enables the BPDU filtering or the BPDU guard feature on Port Fast-enabled interfaces or enables the Port Fast feature on all nontrunking interfaces.


spanning-tree transmit hold-count

Use the spanning-tree transmit hold-count global configuration command to configure the number of bridge protocol data units (BPDUs) sent every second. Use the no form of this command to return to the default setting.

spanning-tree transmit hold-count [value]

no spanning-tree transmit hold-count [value]

Syntax Description

value

(Optional) Number of BPDUs sent every second. The range is 1 to 20.


Defaults

The default is 6.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)SED

This command was introduced.


Usage Guidelines

Increasing the transmit hold-count value can have a significant impact on CPU utilization when the switch is in rapid-per-VLAN spanning-tree plus (rapid-PVST+) mode. Decreasing this value might slow down convergence. We recommend using the default setting.

Examples

This example shows how to set the transmit hold count to 8:

Switch(config)# spanning-tree transmit hold-count 8

You can verify your setting by entering the show spanning-tree mst privileged EXEC command.

Related Commands

Command
Description

show spanning-tree mst

Displays the multiple spanning-tree (MST) region configuration and status, including the transmit hold count.


spanning-tree uplinkfast

Use the spanning-tree uplinkfast global configuration command to accelerate the choice of a new root port when a link or switch fails or when the spanning tree reconfigures itself. Use the no form of this command to return to the default setting.

spanning-tree uplinkfast [max-update-rate pkts-per-second]

no spanning-tree uplinkfast [max-update-rate]

Syntax Description

max-update-rate pkts-per-second

(Optional) The number of packets per second at which update packets are sent. The range is 0 to 32000.


Defaults

UplinkFast is disabled.

The update rate is 150 packets per second.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

Use this command only on access switches.

You can configure the UplinkFast feature for rapid PVST+ or for multiple spanning-tree (MST) mode, but the feature remains disabled (inactive) until you change the spanning-tree mode to PVST+.

When you enable UplinkFast, it is enabled for the entire switch and cannot be enabled for individual VLANs.

When UplinkFast is enabled, the switch priority of all VLANs is set to 49152. If you change the path cost to a value less than 3000 and you enable UplinkFast or UplinkFast is already enabled, the path cost of all interfaces and VLAN trunks is increased by 3000 (if you change the path cost to 3000 or above, the path cost is not altered). The changes to the switch priority and the path cost reduces the chance that a switch will become the root switch.

When UplinkFast is disabled, the switch priorities of all VLANs and path costs of all interfaces are set to default values if you did not modify them from their defaults.

When spanning tree detects that the root port has failed, UplinkFast immediately changes to an alternate root port, changing the new root port directly to forwarding state. During this time, a topology change notification is sent.

Do not enable the root guard on interfaces that will be used by the UplinkFast feature. With UplinkFast, the backup interfaces (in the blocked state) replace the root port in the case of a failure. However, if root guard is also enabled, all the backup interfaces used by the UplinkFast feature are placed in the root-inconsistent state (blocked) and prevented from reaching the forwarding state.

If you set the max-update-rate to 0, station-learning frames are not generated, so the spanning-tree topology converges more slowly after a loss of connectivity.

Examples

This example shows how to enable UplinkFast:

Switch(config)# spanning-tree uplinkfast 

You can verify your setting by entering the show spanning-tree summary privileged EXEC command.

Related Commands

Command
Description

show spanning-tree summary

Displays a summary of the spanning-tree interface states.

spanning-tree vlan root primary

Forces this switch to be the root switch.


spanning-tree vlan

Use the spanning-tree vlan global configuration command to configure spanning tree on a per-VLAN basis. Use the no form of this command to return to the default setting.

spanning-tree vlan vlan-id [forward-time seconds | hello-time seconds | max-age seconds |
priority priority | root {primary | secondary} [diameter net-diameter
[hello-time seconds]]]

no spanning-tree vlan vlan-id [forward-time | hello-time | max-age | priority | root]

Syntax Description

vlan-id

VLAN range associated with a spanning-tree instance. You can specify a single VLAN identified by VLAN ID number, a range of VLANs separated by a hyphen, or a series of VLANs separated by a comma. The range is 1 to 4094.

forward-time seconds

(Optional) Set the forward-delay time for the specified spanning-tree instance. The forwarding time specifies how long each of the listening and learning states last before the interface begins forwarding. The range is 4 to 30 seconds.

hello-time seconds

(Optional) Set the interval between hello bridge protocol data units (BPDUs) sent by the root switch configuration messages. The range is 1 to 10 seconds.

max-age seconds

(Optional) Set the interval between messages the spanning tree receives from the root switch. If a switch does not receive a BPDU message from the root switch within this interval, it recomputes the spanning-tree topology. The range is 6 to 40 seconds.

priority priority

(Optional) Set the switch priority for the specified spanning-tree instance. This setting affects the likelihood that this switch is selected as the root switch. A lower value increases the probability that the switch is selected as the root switch.

The range is 0 to 61440 in increments of 4096. Valid priority values are 4096, 8192, 12288, 16384, 20480, 24576, 28672, 32768, 36864, 40960, 45056, 49152, 53248, 57344, and 61440. All other values are rejected.

root primary

(Optional) Force this switch to be the root switch.

root secondary

(Optional) Set this switch to be the root switch should the primary root switch fail.

diameter net-diameter

(Optional) Set the maximum number of switches between any two end stations. The range is 2 to 7.


Defaults

Spanning tree is enabled on all VLANs.

The forward-delay time is 15 seconds.

The hello time is 2 seconds.

The max-age is 20 seconds.

The primary root switch priority is 24576.

The secondary root switch priority is 28672.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

Disabling the STP causes the VLAN to stop participating in the spanning-tree topology. Interfaces that are administratively down remain down. Received BPDUs are forwarded like other multicast frames. The VLAN does not detect and prevent loops when STP is disabled.

You can disable the STP on a VLAN that is not currently active and verify the change by using the show running-config or the show spanning-tree vlan vlan-id privileged EXEC command. The setting takes effect when the VLAN is activated.

When disabling or re-enabling the STP, you can specify a range of VLANs that you want to disable or enable.

When a VLAN is disabled and then enabled, all assigned VLANs continue to be its members. However, all spanning-tree bridge parameters are returned to their previous settings (the last setting before the VLAN was disabled).

You can enable spanning-tree options on a VLAN that has no interfaces assigned to it. The setting takes effect when you assign interfaces to it.

When setting the max-age seconds, if a switch does not receive BPDUs from the root switch within the specified interval, it recomputes the spanning-tree topology. The max-age setting must be greater than the hello-time setting.

The spanning-tree vlan vlan-id root command should be used only on backbone switches.

When you enter the spanning-tree vlan vlan-id root command, the software checks the switch priority of the current root switch for each VLAN. Because of the extended system ID support, the switch sets the switch priority for the specified VLAN to 24576 if this value will cause this switch to become the root for the specified VLAN. If any root switch for the specified VLAN has a switch priority lower than 24576, the switch sets its own priority for the specified VLAN to 4096 less than the lowest switch priority. (4096 is the value of the least-significant bit of a 4-bit switch priority value.)

When you enter the spanning-tree vlan vlan-id root secondary command, because of support for the extended system ID, the software changes the switch priority from the default value (32768) to 28672. If the root switch should fail, this switch becomes the next root switch (if the other switches in the network use the default switch priority of 32768, and therefore, are unlikely to become the root switch).

Examples

This example shows how to disable the STP on VLAN 5:

Switch(config)# no spanning-tree vlan 5

You can verify your setting by entering the show spanning-tree privileged EXEC command. In this instance, VLAN 5 does not appear in the list.

This example shows how to set the spanning-tree forwarding time to 18 seconds for VLANs 20 and 25:

Switch(config)# spanning-tree vlan 20,25 forward-time 18

This example shows how to set the spanning-tree hello-delay time to 3 seconds for VLANs 20 to 24:

Switch(config)# spanning-tree vlan 20-24 hello-time 3

This example shows how to set spanning-tree max-age to 30 seconds for VLAN 20:

Switch(config)# spanning-tree vlan 20 max-age 30

This example shows how to reset the max-age parameter to the default value for spanning-tree instance 100 and 105 to 108:

Switch(config)# no spanning-tree vlan 100, 105-108 max-age

This example shows how to set the spanning-tree priority to 8192 for VLAN 20:

Switch(config)# spanning-tree vlan 20 priority 8192

This example shows how to configure the switch as the root switch for VLAN 10 with a network diameter of 4:

Switch(config)# spanning-tree vlan 10 root primary diameter 4

This example shows how to configure the switch as the secondary root switch for VLAN 10 with a network diameter of 4:

Switch(config)# spanning-tree vlan 10 root secondary diameter 4 

You can verify your settings by entering the show spanning-tree vlan vlan-id privileged EXEC command.

Related Commands

Command
Description

show spanning-tree vlan

Displays spanning-tree information.

spanning-tree cost

Sets the path cost for spanning-tree calculations.

spanning-tree guard

Enables the root guard or the loop guard feature for all the VLANs associated with the selected interface.

spanning-tree port-priority

Sets an interface priority.

spanning-tree portfast (global configuration)

Globally enables the BPDU filtering or the BPDU guard feature on Port Fast-enabled interfaces or enables the Port Fast feature on all nontrunking interfaces.

spanning-tree portfast (interface configuration)

Enables the Port Fast feature on an interface in all its associated VLANs.

spanning-tree uplinkfast

Enables the UplinkFast feature, which accelerates the choice of a new root port.


speed

Use the speed interface configuration command to specify the speed of a 10/100 Mb/s or 10/100/1000 Mb/s port. Use the no or default form of this command to return the port to its default value.

speed {10 | 100 | 1000 | auto [10 | 100 | 1000] | nonegotiate}

no speed

Syntax Description

10

Port runs at 10 Mb/s.

100

Port runs at 100 Mb/s.

1000

Port runs at 1000 Mb/s. This option is valid and visible only on 10/100/1000 Mb/s-ports.

auto

Port automatically detects the speed it should run at based on the port at the other end of the link. If you use the 10, 100, or 1000 keywords with the auto keyword, the port only autonegotiates at the specified speeds.

nonegotiate

Autonegotiation is disabled, and the port runs at 1000 Mb/s. (The 1000BASE-T SFP does not support the nonegotiate keyword.)


Defaults

The default is auto.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

If an SFP module port is connected to a device that does not support autonegotiation, you can configure the speed to not negotiate (nonegotiate).

If the speed is set to auto, the switch negotiates with the device at the other end of the link for the speed setting and then forces the speed setting to the negotiated value. The duplex setting remains as configured on each end of the link, which could result in a duplex setting mismatch.

If both ends of the line support autonegotiation, we highly recommend the default autonegotiation settings. If one interface supports autonegotiation and the other end does not, do use the auto setting on the supported side, but set the duplex and speed on the other side.


Caution Changing the interface speed and duplex mode configuration might shut down and re-enable the interface during the reconfiguration.

For guidelines on setting the switch speed and duplex parameters, see the "Configuring Interface Characteristics" chapter in the software configuration guide for this release.

Examples

This example shows how to set the speed on a port to 100 Mb/s:

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# speed 100

This example shows how to set a port to autonegotiate at only 10 Mb/s:

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# speed auto 10

This example shows how to set a port to autonegotiate at only 10 or 100 Mb/s:

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# speed auto 10 100 

You can verify your settings by entering the show interfaces privileged EXEC command.

Related Commands

Command
Description

duplex

Specifies the duplex mode of operation.

show interfaces

Displays the statistical information specific to all interfaces or to a specific interface.


srr-queue bandwidth limit

Use the srr-queue bandwidth limit interface configuration command to limit the maximum output on a port. Use the no form of this command to return to the default setting.

srr-queue bandwidth limit weight1

no srr-queue bandwidth limit


Note To use this command, the switch must be running the LAN Base image.


Syntax Description

weight1

Percentage of the port speed to which the port should be limited. The range is 10 to 90.


Defaults

The port is not rate limited and is set to 100 percent.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

If you configure this command to 80 percent, the port is idle 20 percent of the time. The line rate drops to 80 percent of the connected speed. These values are not exact because the hardware adjusts the line rate in increments of six.


Note The egress queue default settings are suitable for most situations. You should change them only when you have a thorough understanding of the egress queues and if these settings do not meet your quality of service (QoS) solution.


Examples

This example shows how to limit a port to 800 Mb/s:

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# srr-queue bandwidth limit 80

You can verify your settings by entering the show mls qos interface [interface-id] queueing privileged EXEC command.

Related Commands

Command
Description

mls qos queue-set output buffers

Allocates buffers to the queue-set.

mls qos srr-queue output cos-map

Maps class of service (CoS) values to egress queue or maps CoS values to a queue and to a threshold ID.

mls qos srr-queue output dscp-map

Maps Differentiated Services Code Point (DSCP) values to an egress queue or maps DSCP values to a queue and to a threshold ID.

mls qos queue-set output threshold

Configures the weighted tail-drop (WTD) thresholds, guarantees the availability of buffers, and configures the maximum memory allocation for the queue-set.

queue-set

Maps a port to a queue-set.

show mls qos interface queueing

Displays QoS information.

srr-queue bandwidth shape

Assigns the shaped weights and enables bandwidth shaping on the four egress queues mapped to a port.

srr-queue bandwidth share

Assigns the shared weights and enables bandwidth sharing on the four egress queues mapped to a port.


srr-queue bandwidth shape

Use the srr-queue bandwidth shape interface configuration command to assign the shaped weights and to enable bandwidth shaping on the four egress queues mapped to a port. Use the no form of this command to return to the default setting.

srr-queue bandwidth shape weight1 weight2 weight3 weight4

no srr-queue bandwidth shape


Note To use this command, the switch must be running the LAN Base image.


Syntax Description

weight1 weight2 weight3 weight4

Specify the weights to specify the percentage of the port that is shaped. The inverse ratio (1/weight) specifies the shaping bandwidth for this queue. Separate each value with a space. The range is 0 to 65535.


Defaults

Weight1 is set to 25. Weight2, weight3, and weight4 are set to 0, and these queues are in shared mode.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

In shaped mode, the queues are guaranteed a percentage of the bandwidth, and they are rate-limited to that amount. Shaped traffic does not use more than the allocated bandwidth even if the link is idle. Use shaping to smooth bursty traffic or to provide a smoother output over time.

The shaped mode overrides the shared mode.

If you configure a shaped queue weight to 0 by using the srr-queue bandwidth shape interface configuration command, this queue participates in shared mode. The weight specified with the srr-queue bandwidth shape command is ignored, and the weights specified with the srr-queue bandwidth share interface configuration command for a queue come into effect.

When configuring queues for the same port for both shaping and sharing, make sure that you configure the lowest numbered queue for shaping.


Note The egress queue default settings are suitable for most situations. You should change them only when you have a thorough understanding of the egress queues and if these settings do not meet your QoS solution.


Examples

This example shows how to configure the queues for the same port for both shaping and sharing. Because the weight ratios for queues 2, 3, and 4 are set to 0, these queues operate in shared mode. The bandwidth weight for queue 1 is 1/8, which is 12.5 percent. Queue 1 is guaranteed this bandwidth and limited to it; it does not extend its slot to the other queues even if the other queues have no traffic and are idle. Queues 2, 3, and 4 are in shared mode, and the setting for queue 1 is ignored. The bandwidth ratio allocated for the queues in shared mode is 4/(4+4+4), which is 33 percent:

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# srr-queue bandwidth shape 8 0 0 0
Switch(config-if)# srr-queue bandwidth share 4 4 4 4

You can verify your settings by entering the show mls qos interface [interface-id] queueing privileged EXEC command.

Related Commands

Command
Description

mls qos queue-set output buffers

Allocates buffers to a queue-set.

mls qos srr-queue output cos-map

Maps class of service (CoS) values to an egress queue or maps CoS values to a queue and to a threshold ID.

mls qos srr-queue output dscp-map

Maps Differentiated Services Code Point (DSCP) values to an egress queue or maps DSCP values to a queue and to a threshold ID.

mls qos queue-set output threshold

Configures the weighted tail-drop (WTD) thresholds, guarantees the availability of buffers, and configures the maximum memory allocation to a queue-set.

priority-queue

Enables the egress expedite queue on a port.

queue-set

Maps a port to a queue-set.

show mls qos interface queueing

Displays quality of service (QoS) information.

srr-queue bandwidth share

Assigns the shared weights and enables bandwidth sharing on the four egress queues mapped to a port.


srr-queue bandwidth share

Use the srr-queue bandwidth share interface configuration command switch to assign the shared weights and to enable bandwidth sharing on the four egress queues mapped to a port. The ratio of the weights is the ratio of frequency in which the shaped round robin (SRR) scheduler dequeues packets from each queue. Use the no form of this command to return to the default setting.

srr-queue bandwidth share weight1 weight2 weight3 weight4

no srr-queue bandwidth share


Note To use this command, the switch must be running the LAN Base image.


Syntax Description

weight1 weight2 weight3 weight4

The ratios of weight1, weight2, weight3, and weight4 specify the ratio of the frequency in which the SRR scheduler dequeues packets. Separate each value with a space. The range is 1 to 255.


Defaults

Weight1, weight2, weight3, and weight4 are 25 (1/4 of the bandwidth is allocated to each queue).

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

The absolute value of each weight is meaningless, and only the ratio of parameters is used.

In shared mode, the queues share the bandwidth among them according to the configured weights. The bandwidth is guaranteed at this level but not limited to it. For example, if a queue empties and does not require a share of the link, the remaining queues can expand into the unused bandwidth and share it among themselves.

If you configure a shaped queue weight to 0 by using the srr-queue bandwidth shape interface configuration command, this queue participates in SRR shared mode. The weight specified with the srr-queue bandwidth shape command is ignored, and the weights specified with the srr-queue bandwidth share interface configuration command for a queue take effect.

When configuring queues for the same port for both shaping and sharing, make sure that you configure the lowest numbered queue for shaping.


Note The egress queue default settings are suitable for most situations. You should change them only when you have a thorough understanding of the egress queues and if these settings do not meet your QoS solution.


Examples

This example shows how to configure the weight ratio of the SRR scheduler running on an egress port. Four queues are used. The bandwidth ratio allocated for each queue in shared mode is 1/(1+2+3+4), 2/(1+2+3+4), 3/(1+2+3+4), and 4/(1+2+3+4), which is 10 percent, 20 percent, 30 percent, and 40 percent for queues 1, 2, 3, and 4. This means that queue 4 has four times the bandwidth of queue 1, twice the bandwidth of queue 2, and one-and-a-third times the bandwidth of queue 3.

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# srr-queue bandwidth share 1 2 3 4

You can verify your settings by entering the show mls qos interface [interface-id] queueing privileged EXEC command.

Related Commands

Command
Description

mls qos queue-set output buffers

Allocates buffers to a queue-set.

mls qos srr-queue output cos-map

Maps class of service (CoS) values to an egress queue or maps CoS values to a queue and to a threshold ID.

mls qos srr-queue output dscp-map

Maps Differentiated Services Code Point (DSCP) values to an egress queue or maps DSCP values to a queue and to a threshold ID.

mls qos queue-set output threshold

Configures the weighted tail-drop (WTD) thresholds, guarantees the availability of buffers, and configures the maximum memory allocation to a queue-set.

priority-queue

Enables the egress expedite queue on a port.

queue-set

Maps a port to a queue-set.

show mls qos interface queueing

Displays quality of service (QoS) information.

srr-queue bandwidth shape

Assigns the shaped weights and enables bandwidth shaping on the four egress queues mapped to a port.


storm-control

Use the storm-control interface configuration command to enable broadcast, multicast, or unicast storm control and to set threshold levels on an interface. Use the no form of this command to return to the default setting.

storm-control {{broadcast | multicast | unicast} level {level [level-low] | bps bps [bps-low] | pps pps [pps-low]}} | {action {shutdown | trap}}

no storm-control {{broadcast | multicast | unicast} level} | {action {shutdown | trap}}

Syntax Description

broadcast

Enable broadcast storm control on the interface.

multicast

Enable multicast storm control on the interface.

unicast

Enable unicast storm control on the interface.

level level [level-low]

Specify the rising and falling suppression levels as a percentage of total bandwidth of the port.

levelRising suppression level, up to two decimal places. The range is 0.00 to 100.00. Block the flooding of storm packets when the value specified for level is reached.

level-low(Optional) Falling suppression level, up to two decimal places. The range is 0.00 to 100.00. This value must be less than or equal to the rising suppression value. If you do not configure a falling suppression level, it is set to the rising suppression level.

level bps bps [bps-low]

Specify the rising and falling suppression levels as a rate in bits per second at which traffic is received on the port.

bpsRising suppression level, up to 1 decimal place. The range is 0.0 to 10000000000.0. Block the flooding of storm packets when the value specified for bps is reached.

bps-low(Optional) Falling suppression level, up to 1 decimal place. The range is 0.0 to 10000000000.0. This value must be equal to or less than the rising suppression value.

You can use metric suffixes such as k, m, and g for large number thresholds.

level pps pps [pps-low]

Specify the rising and falling suppression levels as a rate in packets per second at which traffic is received on the port.

ppsRising suppression level, up to 1 decimal place. The range is 0.0 to 10000000000.0. Block the flooding of storm packets when the value specified for pps is reached.

pps-low(Optional) Falling suppression level, up to 1 decimal place. The range is 0.0 to 10000000000.0. This value must be equal to or less than the rising suppression value.

You can use metric suffixes such as k, m, and g for large number thresholds.

action {shutdown | trap}

Action taken when a storm occurs on a port. The default action is to filter traffic and to not send an Simple Network Management Protocol (SNMP) trap.

The keywords have these meanings:

shutdown—Disables the port during a storm.

trap—Sends an SNMP trap when a storm occurs.


Defaults

Broadcast, multicast, and unicast storm control are disabled.

The default action is to filter traffic and to not send an SNMP trap.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

The storm-control suppression level can be entered as a percentage of total bandwidth of the port, as a rate in packets per second at which traffic is received, or as a rate in bits per second at which traffic is received.

When specified as a percentage of total bandwidth, a suppression value of 100 percent means that no limit is placed on the specified traffic type. A value of level 0 0 means that all broadcast, multicast, or unicast traffic on that port is blocked. Storm control is enabled only when the rising suppression level is less than 100 percent. If no other storm-control configuration is specified, the default action is to filter the traffic causing the storm and to send no SNMP traps.


Note When the storm control threshold for multicast traffic is reached, all multicast traffic except control traffic, such as bridge protocol data unit (BDPU) and Cisco Discovery Protocol (CDP) frames, are blocked.


The trap and shutdown options are independent of each other.

If you configure the action to be taken as shutdown (the port is error-disabled during a storm) when a packet storm is detected, you must use the no shutdown interface configuration command to bring the interface out of this state. If you do not specify the shutdown action, specify the action as trap (the switch generates a trap when a storm is detected).

When a storm occurs and the action is to filter traffic, if the falling suppression level is not specified, the switch blocks all traffic until the traffic rate drops below the rising suppression level. If the falling suppression level is specified, the switch blocks traffic until the traffic rate drops below this level.


Note Storm control is supported on physical interfaces. You can also configure storm control on an EtherChannel. When storm control is configured on an EtherChannel, the storm control settings propagate to the EtherChannel physical interfaces.


When a broadcast storm occurs and the action is to filter traffic, the switch blocks only broadcast traffic.

For more information, see the software configuration guide for this release.

Examples

This example shows how to enable broadcast storm control with a 75.5-percent rising suppression level:

Switch(config-if)# storm-control broadcast level 75.5

This example shows how to enable unicast storm control on a port with a 87-percent rising suppression level and a 65-percent falling suppression level:

Switch(config-if)# storm-control unicast level 87 65

This example shows how to enable multicast storm control on a port with a 2000-packets-per-second rising suppression level and a 1000-packets-per-second falling suppression level:

Switch(config-if)# storm-control multicast level pps 2k 1k

This example shows how to enable the shutdown action on a port:

Switch(config-if)# storm-control action shutdown

You can verify your settings by entering the show storm-control privileged EXEC command.

Related Commands

Command
Description

show storm-control

Displays broadcast, multicast, or unicast storm control settings on all interfaces or on a specified interface.


switchport access

Use the switchport access interface configuration command to configure a port as a static-access or dynamic-access port. If the switchport mode is set to access, the port operates as a member of the specified VLAN. If set to dynamic, the port starts discovery of VLAN assignment based on the incoming packets it receives. Use the no form of this command to reset the access mode to the default VLAN for the switch.

switchport access vlan {vlan-id | dynamic}

no switchport access vlan

Syntax Description

vlan vlan-id

Configure the interface as a static access port with the VLAN ID of the access mode VLAN; the range is 1 to 4094.

vlan dynamic

Specify that the access mode VLAN is dependent on the VLAN Membership Policy Server (VMPS) protocol. The port is assigned to a VLAN based on the source MAC address of a host (or hosts) connected to the port. The switch sends every new MAC address received to the VMPS server to get the VLAN name to which the dynamic-access port should be assigned. If the port already has a VLAN assigned and the source has already been approved by the VMPS, the switch forwards the packet to the VLAN.


Defaults

The default access VLAN and trunk interface native VLAN is a default VLAN corresponding to the platform or interface hardware.

A dynamic-access port is initially a member of no VLAN and receives its assignment based on the packet it receives.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

The no switchport access command resets the access mode VLAN to the appropriate default VLAN for the device.

The port must be in access mode before the switchport access vlan command can take effect.

An access port can be assigned to only one VLAN.

The VMPS server (such as a Catalyst 6000 series switch) must be configured before a port is configured as dynamic.

These restrictions apply to dynamic-access ports:

The software implements the VLAN Query Protocol (VQP) client, which can query a VMPS such as a Catalyst 6000 series switch. The Catalyst 2960 switches are not VMPS servers. The VMPS server must be configured before a port is configured as dynamic.

Use dynamic-access ports only to connect end stations. Connecting them to switches or routers (that use bridging protocols) can cause a loss of connectivity.

Configure the network so that STP does not put the dynamic-access port into an STP blocking state. The Port Fast feature is automatically enabled on dynamic-access ports.

Dynamic-access ports can only be in one VLAN and do not use VLAN tagging.

Dynamic-access ports cannot be configured as

Members of an EtherChannel port group (dynamic-access ports cannot be grouped with any other port, including other dynamic ports).

Source or destination ports in a static address entry.

Monitor ports.

Examples

This example shows how to change a switched port interface that is operating in access mode to operate in VLAN 2 instead of the default VLAN:

Switch(config-if)# switchport access vlan 2

You can verify your setting by entering the show interfaces interface-id switchport privileged EXEC command and examining information in the Administrative Mode and Operational Mode rows.

Related Commands

Command
Description

show interfaces switchport

Displays the administrative and operational status of a switching port, including port blocking and port protection settings.

switchport mode

Configures the VLAN membership mode of a port.


switchport backup interface

Use the switchport backup interface interface configuration command on a Layer 2 interface to configure Flex Links, a pair of interfaces that provide backup to each other. Use the no form of this command to remove the Flex Links configuration.

switchport backup interface [FastEthernet interface-id | GigabitEthernet interface-id | Port-channel interface-id | TenGigabitEthernet interface-id ] {mmu primary vlan interface-id | multicast fast-convergence | preemption {delay delay-time | mode} | prefer vlan vlan-id}

no switchport backup interface [FastEthernet interface-id | GigabitEthernet interface-id | Port-channel interface-id | TenGigabitEthernet interface-id ] {mmu primary vlan interface-id | multicast fast-convergence | preemption {delay delay-time | mode} | prefer vlan vlan-id}


Note To use this command, the switch must be running the LAN Base image.


Syntax Description

FastEthernet

FastEthernet IEEE 802.3 port name. Valid range is 0 to 9.

GigabitEthernet

GigabitEthernet IEEE 802.3z port name. Valid range is 0 to 9.

Port-channel

Ethernet Channel of interface. Valid range is 0 to 48.

TenGigabitEthernet

Ten Gigabit Ethernet port name. Valid range is 0 to 9.

interface-id

Specify that the Layer 2 interface to act as a backup link to the interface being configured. The interface can be a physical interface or port channel. The port-channel range is 1 to 486.

mmu

MAC-address move update. Configure the MAC move update (MMU) for a backup interface pair.

primary vlan vlan-id

The VLAN ID of the private-VLAN primary VLAN; valid range is 1 to 4,094.

multicast fast-convergence

Multicast Fast-convergence parameter.

preemption

Configure a preemption scheme for a backup interface pair.

delay delay-time

(Optional) Specify a preemption delay; the valid values are 1 to 300 seconds.

mode

Specify a preemption mode as bandwidth, forced, or off.

prefer vlan vlan-id

Specify that VLANs are carried on the backup interfaces of a Flex Link pair. VLAN ID range is 1 to 4,094.

off

(Optional) Specify that no preemption occurs from backup to active.

delay delay-time

(Optional) Specify a preemption delay; the valid values are 1 to 300 seconds.


Defaults

The default is to have no Flex Links defined. Preemption mode is off. No preemption occurs. Preemption delay is set to 35 seconds.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.

12.2(25)SEE

Added preemption, mode, forced, bandwidth, off, and delay keywords.

12.2(37)SE

Added prefer vlan keyword.

12.2(44)SE

The multicast, fast-convergence, delay, mode, prefer, and vlan keywords were added.


Usage Guidelines

With Flex Links configured, one link acts as the primary interface and forwards traffic, while the other interface is in standby mode, ready to begin forwarding traffic if the primary link shuts down. The interface being configured is referred to as the active link; the specified interface is identified as the backup link. The feature provides an alternative to the Spanning Tree Protocol (STP), allowing users to turn off STP and still retain basic link redundancy.

This command is available only for Layer 2 interfaces.

You can configure only one Flex Link backup link for any active link, and it must be a different interface from the active interface.

An interface can belong to only one Flex Link pair. An interface can be a backup link for only one active link. An active link cannot belong to another Flex Link pair.

A backup link does not have to be the same type (Fast Ethernet or Gigabit Ethernet, for instance) as the active link. However, you should configure both Flex Links with similar characteristics so that there are no loops or changes in behavior if the standby link begins to forward traffic.

Neither of the links can be a port that belongs to an EtherChannel. However, you can configure two port channels (EtherChannel logical interfaces) as Flex Links, and you can configure a port channel and a physical interface as Flex Links, with either the port channel or the physical interface as the active link.

If STP is configured on the switch, Flex Links do not participate in STP in all valid VLANs. If STP is not running, be sure that there are no loops in the configured topology.

Examples

This example shows how to configure two interfaces as Flex Links:

Switch# configure terminal 
Switch(conf)# interface fastethernet0/1
Switch(conf-if)# switchport backup interface fastethernet0/2
Switch(conf-if)# end

This example shows how to configure the Fast Ethernet interface to always preempt the backup:

Switch# configure terminal 
Switch(conf)# interface fastethernet0/1
Switch(conf-if)# switchport backup interface fastethernet0/2 preemption forced
Switch(conf-if)# end

This example shows how to configure the Fast Ethernet interface preemption delay time:

Switch# configure terminal 
Switch(conf)# interface fastethernet0/1
Switch(conf-if)# switchport backup interface fastethernet0/2 preemption delay 150
Switch(conf-if)# end

This example shows how to configure the Fast Ethernet interface as the MMU primary VLAN:

Switch# configure terminal 
Switch(conf)# interface fastethernet0/1
Switch(conf-if)# switchport backup interface fastethernet0/2 mmu primary vlan 1021
Switch(conf-if)# end

You can verify your setting by entering the show interfaces switchport backup privileged EXEC 
command.

The following example shows how to configure preferred VLANs:

Switch(config)# interface gigabitethernet 0/6
Switch(config-if)# switchport backup interface gigabitethernet 0/8 prefer vlan 60,100-120

You can verify your setting by entering the show interfaces switchport backup privileged EXEC command.

In the following example, VLANs 60, and 100 to 120 are configured on the switch:

Switch(config)# interface gigabitEthernet 0/6
Switch(config-if)# switchport backup interface gigabitEthernet 0/8 prefer vlan 60,100-120

When both interfaces are up, Gi0/6 forwards traffic for VLANs 1 to 50, and Gi0/8 forwards traffic for VLANs 60 and 100 to 120.

Switch# show interfaces switchport backup
Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
GigabitEthernet0/6 GigabitEthernet0/8 Active Up/Backup Up

Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120

When a Flex Link interface goes down (LINK_DOWN), VLANs preferred on this interface are moved to the peer interface of the Flex Link pair. In this example, if interface Gi0/6 goes down, Gi0/8 carries all VLANs of the Flex Link pair.

Switch# show interfaces switchport backup
Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
GigabitEthernet0/6 GigabitEthernet0/8 Active Down/Backup Up

Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120

When a Flex Link interface comes up, VLANs preferred on this interface are blocked on the peer interface and moved to the forwarding state on the interface that has just come up. In this example, if interface Gi0/6 comes up, VLANs preferred on this interface are blocked on the peer interface Gi0/8 and forwarded on Gi0/6.

Switch# show interfaces switchport backup
Switch Backup Interface Pairs:

Active Interface        Backup Interface        State
------------------------------------------------------------------------
GigabitEthernet0/6 GigabitEthernet0/8 Active Up/Backup Up

Vlans Preferred on Active Interface: 1-50
Vlans Preferred on Backup Interface: 60, 100-120

This example shows how to configure multicast fast-convergence on interface Gi0/11:

Switch# configure terminal 
Switch(config)# interface gigabitEthernet 0/11
Switch(config-if)# switchport backup interface gigabitEthernet 0/12 multicast 
fast-convergence
Switch(config-if)# end
 

You can verify your setting by entering the show interfaces switchport backup detail privileged EXEC command.

 
Switch# show interfaces switchport backup detail 
 
Switch Backup Interface Pairs:
 
Active Interface        Backup Interface        State
------------------------------------------------------------------------
GigabitEthernet0/11 GigabitEthernet0/12 Active Up/Backup Standby
        Preemption Mode  : off
        Multicast Fast Convergence  : On
        Bandwidth : 1000000 Kbit (Gi0/11), 1000000 Kbit (Gi0/12)
        Mac Address Move Update Vlan : auto

Related Commands

Command
Description

show interfaces [interface-id] switchport backup

Displays the configured Flex Links and their status on the switch or for the specified interface.


switchport block

Use the switchport block interface configuration command to prevent unknown multicast or unicast packets from being forwarded. Use the no form of this command to allow forwarding unknown multicast or unicast packets.

switchport block {multicast | unicast}

no switchport block {multicast | unicast}

Syntax Description

multicast

Specify that unknown multicast traffic should be blocked.

Note Only pure Layer 2 multicast traffic is blocked. Multicast packets that contain IPv4 or IPv6 information in the header are not blocked.

unicast

Specify that unknown unicast traffic should be blocked.


Defaults

Unknown multicast and unicast traffic is not blocked.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

By default, all traffic with unknown MAC addresses is sent to all ports. You can block unknown multicast or unicast traffic on protected or nonprotected ports. If unknown multicast or unicast traffic is not blocked on a protected port, there could be security issues.

With multicast traffic, the port blocking feature blocks only pure Layer 2 packets. Multicast packets that contain IPv4 or IPv6 information in the header are not blocked.

Blocking unknown multicast or unicast traffic is not automatically enabled on protected ports; you must explicitly configure it.

For more information about blocking packets, see the software configuration guide for this release.

Examples

This example shows how to block unknown unicast traffic on an interface:

Switch(config-if)# switchport block unicast

You can verify your setting by entering the show interfaces interface-id switchport privileged EXEC command.

Related Commands

Command
Description

show interfaces switchport

Displays the administrative and operational status of a switching port, including port blocking and port protection settings.


switchport host

Use the switchport host interface configuration command to optimize a port for a host connection. The no form of this command has no affect on the system.

switchport host

Syntax Description

This command has no arguments or keywords.

Defaults

The default is for the port to not be optimized for a host connection.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

To optimize the port for a host connection, the switchport host command sets switch port mode to access, enables spanning tree Port Fast, and disables channel grouping. Only an end station can accept this configuration.

Because spanning tree Port Fast is enabled, you should enter the switchport host command only on ports that are connected to a single host. Connecting other switches, hubs, concentrators, or bridges to a fast-start port can cause temporary spanning-tree loops.

Enable the switchport host command to decrease the time that it takes to start up packet forwarding.

Examples

This example shows how to optimize the port configuration for a host connection:

Switch(config-if)# switchport host 
switchport mode will be set to access 
spanning-tree portfast will be enabled 
channel group will be disabled 
Switch(config-if)# 

You can verify your setting by entering the show interfaces interface-id switchport privileged EXEC command.

Related Commands

Command
Description

show interfaces switchport

Displays the administrative and operational status of a switching port, including switchport mode.


switchport mode

Use the switchport mode interface configuration command to configure the VLAN membership mode of a port. Use the no form of this command to reset the mode to the appropriate default for the device.

switchport mode {access | dynamic {auto | desirable} | trunk}

no switchport mode {access | dynamic | trunk}

Syntax Description

access

Set the port to access mode (either static-access or dynamic-access depending on the setting of the switchport access vlan interface configuration command). The port is set to access unconditionally and operates as a nontrunking, single VLAN interface that sends and receives nonencapsulated (non-tagged) frames. An access port can be assigned to only one VLAN.

dynamic auto

Set the interface trunking mode dynamic parameter to auto to specify that the interface convert the link to a trunk link. This is the default switchport mode.

dynamic desirable

Set the interface trunking mode dynamic parameter to desirable to specify that the interface actively attempt to convert the link to a trunk link.

trunk

Set the port to trunk unconditionally. The port is a trunking VLAN Layer 2 interface. The port sends and receives encapsulated (tagged) frames that identify the VLAN of origination. A trunk is a point-to-point link between two switches or between a switch and a router.


Defaults

The default mode is dynamic auto.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

A configuration that uses the access or trunk keywords takes effect only when you configure the port in the appropriate mode by using the switchport mode command. The static-access and trunk configuration are saved, but only one configuration is active at a time.

When you enter access mode, the interface changes to permanent nontrunking mode and negotiates to convert the link into a nontrunk link even if the neighboring interface does not agree to the change.

When you enter trunk mode, the interface changes to permanent trunking mode and negotiates to convert the link into a trunk link even if the interface connecting to it does not agree to the change.

When you enter dynamic auto mode, the interface converts the link to a trunk link if the neighboring interface is set to trunk or desirable mode.

When you enter dynamic desirable mode, the interface becomes a trunk interface if the neighboring interface is set to trunk, desirable, or auto mode.

To autonegotiate trunking, the interfaces must be in the same VLAN Trunking Protocol (VTP) domain. Trunk negotiation is managed by the Dynamic Trunking Protocol (DTP), which is a point-to-point protocol. However, some internetworking devices might forward DTP frames improperly, which could cause misconfigurations. To avoid this, you should configure interfaces connected to devices that do not support DTP to not forward DTP frames, which turns off DTP.

If you do not intend to trunk across those links, use the switchport mode access interface configuration command to disable trunking.

To enable trunking to a device that does not support DTP, use the switchport mode trunk and switchport nonegotiate interface configuration commands to cause the interface to become a trunk but to not generate DTP frames.

Access ports and trunk ports are mutually exclusive.

The IEEE 802.1x feature interacts with switchport modes in these ways:

If you try to enable IEEE 802.1x on a trunk port, an error message appears, and IEEE 802.1x is not enabled. If you try to change the mode of an IEEE 802.1x-enabled port to trunk, the port mode is not changed.

If you try to enable IEEE 802.1x on a port set to dynamic auto or dynamic desirable, an error message appears, and IEEE 802.1x is not enabled. If you try to change the mode of an IEEE 802.1x-enabled port to dynamic auto or dynamic desirable, the port mode is not changed.

If you try to enable IEEE 802.1x on a dynamic-access (VLAN Query Protocol [VQP]) port, an error message appears, and IEEE 802.1x is not enabled. If you try to change an IEEE 802.1x-enabled port to dynamic VLAN assignment, an error message appears, and the VLAN configuration is not changed.

Examples

This example shows how to configure a port for access mode:

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# switchport mode access

This example shows how set the port to dynamic desirable mode:

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# switchport mode dynamic desirable

This example shows how to configure a port for trunk mode:

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# switchport mode trunk

You can verify your settings by entering the show interfaces interface-id switchport privileged EXEC command and examining information in the Administrative Mode and Operational Mode rows.

Related Commands

Command
Description

show interfaces switchport

Displays the administrative and operational status of a switching port, including port blocking and port protection settings.

switchport access

Configures a port as a static-access or dynamic-access port.

switchport trunk

Configures the trunk characteristics when an interface is in trunking mode.


switchport nonegotiate

Use the switchport nonegotiate interface configuration command to specify that Dynamic Trunking Protocol (DTP) negotiation packets are not sent on the Layer 2 interface. The switch does not engage in DTP negotiation on this interface. Use the no form of this command to return to the default setting.

switchport nonegotiate

no switchport nonegotiate

Syntax Description

This command has no arguments or keywords.

Defaults

The default is to use DTP negotiation to learn the trunking status.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

The no form of the switchport nonegotiate command removes nonegotiate status.

This command is valid only when the interface switchport mode is access or trunk (configured by using the switchport mode access or the switchport mode trunk interface configuration command). This command returns an error if you attempt to execute it in dynamic (auto or desirable) mode.

Internetworking devices that do not support DTP might forward DTP frames improperly and cause misconfigurations. To avoid this, you should turn off DTP by using the switchport no negotiate command to configure the interfaces connected to devices that do not support DTP to not forward DTP frames.

When you enter the switchport nonegotiate command, DTP negotiation packets are not sent on the interface. The device does or does not trunk according to the mode parameter: access or trunk.

If you do not intend to trunk across those links, use the switchport mode access interface configuration command to disable trunking.

To enable trunking on a device that does not support DTP, use the switchport mode trunk and switchport nonegotiate interface configuration commands to cause the interface to become a trunk but to not generate DTP frames.

Examples

This example shows how to cause a port to refrain from negotiating trunking mode and to act as a trunk or access port (depending on the mode set):

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# switchport nonegotiate

You can verify your setting by entering the show interfaces interface-id switchport privileged EXEC command.

Related Commands

Command
Description

show interfaces switchport

Displays the administrative and operational status of a switching port, including port blocking and port protection settings.

switchport mode

Configures the VLAN membership mode of a port.


switchport port-security

Use the switchport port-security interface configuration command without keywords to enable port security on the interface. Use the keywords to configure secure MAC addresses, sticky MAC address learning, a maximum number of secure MAC addresses, or the violation mode. Use the no form of this command to disable port security or to set the parameters to their default states.

switchport port-security [mac-address mac-address [vlan {vlan-id | {access | voice}}] | mac-address sticky [mac-address | vlan {vlan-id | {access | voice}}]] [maximum value [vlan {vlan-list | {access | voice}}]]

no switchport port-security [mac-address mac-address [vlan {vlan-id | {access | voice}}] | mac-address sticky [mac-address | vlan {vlan-id | {access | voice}}]] [maximum value [vlan {vlan-list | {access | voice}}]]

switchport port-security [aging] [violation {protect | restrict | shutdown | shutdown vlan}]

no switchport port-security [aging] [violation {protect | restrict | shutdown | shutdown vlan}]

Syntax Description

aging

(Optional) See the switchport port-security aging command.

mac-address mac-address

(Optional) Specify a secure MAC address for the interface by entering a 48-bit MAC address. You can add additional secure MAC addresses up to the maximum value configured.

vlan vlan-id

(Optional) On a trunk port only, specify the VLAN ID and the MAC address. If no VLAN ID is specified, the native VLAN is used.

vlan access

(Optional) On an access port only, specify the VLAN as an access VLAN.

vlan voice

(Optional) On an access port only, specify the VLAN as a voice VLAN.

Note The voice keyword is available only if voice VLAN is configured on a port and if that port is not the access VLAN.

mac-address sticky [mac-address]

(Optional) Enable the interface for sticky learning by entering only the mac-address sticky keywords. When sticky learning is enabled, the interface adds all secure MAC addresses that are dynamically learned to the running configuration and converts these addresses to sticky secure MAC addresses.

(Optional) Enter a mac-address to specify a sticky secure MAC address.

maximum value

(Optional) Set the maximum number of secure MAC addresses for the interface.The maximum number of secure MAC addresses that you can configure on a switch is set by the maximum number of available MAC addresses allowed in the system. This number represents the total of available MAC addresses, including those used for other Layer 2 functions and any other secure MAC addresses configured on interfaces.

The default setting is 1.

vlan [vlan-list]

(Optional) For trunk ports, you can set the maximum number of secure MAC addresses on a VLAN. If the vlan keyword is not entered, the default value is used.

vlan—set a per-VLAN maximum value.

vlan vlan-list—set a per-VLAN maximum value on a range of VLANs separated by a hyphen or a series of VLANs separated by commas. For nonspecified VLANs, the per-VLAN maximum value is used.

violation

(Optional) Set the security violation mode or the action to be taken if port security is violated. The default is shutdown.

protect

Set the security violation protect mode. In this mode, when the number of port secure MAC addresses reaches the maximum limit allowed on the port, packets with unknown source addresses are dropped until you remove a sufficient number of secure MAC addresses to drop below the maximum value or increase the number of maximum allowable addresses. You are not notified that a security violation has occurred.

Note We do not recommend configuring the protect mode on a trunk port. The protect mode disables learning when any VLAN reaches its maximum limit, even if the port has not reached its maximum limit.

restrict

Set the security violation restrict mode. In this mode, when the number of secure MAC addresses reaches the limit allowed on the port, packets with unknown source addresses are dropped until you remove a sufficient number of secure MAC addresses or increase the number of maximum allowable addresses. An SNMP trap is sent, a syslog message is logged, and the violation counter increments.

shutdown

Set the security violation shutdown mode. In this mode, the interface is error-disabled when a violation occurs and the port LED turns off. An SNMP trap is sent, a syslog message is logged, and the violation counter increments. When a secure port is in the error-disabled state, you can bring it out of this state by entering the errdisable recovery cause psecure-violation global configuration command, or you can manually re-enable it by entering the shutdown and no shut down interface configuration commands.

shutdown vlan

Set the security violation mode to per-VLAN shutdown. In this mode, only the VLAN on which the violation occurred is error-disabled.


Defaults

The default is to disable port security.

When port security is enabled and no keywords are entered, the default maximum number of secure MAC addresses is 1.

The default violation mode is shutdown.

Sticky learning is disabled.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.

12.2(35)SE

The shutdown vlan keyword was added


Usage Guidelines

A secure port has the following limitations:

A secure port can be an access port or a trunk port; it cannot be a dynamic access port.

A secure port cannot be a protected port.

A secure port cannot be a destination port for Switched Port Analyzer (SPAN).

A secure port cannot belong to a Fast EtherChannel or Gigabit EtherChannel port group.

You cannot configure static secure or sticky secure MAC addresses in the voice VLAN.

When you enable port security on an interface that is also configured with a voice VLAN, set the maximum allowed secure addresses on the port to two. When the port is connected to a Cisco IP phone, the IP phone requires one MAC address. The Cisco IP phone address is learned on the voice VLAN, but is not learned on the access VLAN. If you connect a single PC to the Cisco IP phone, no additional MAC addresses are required. If you connect more than one PC to the Cisco IP phone, you must configure enough secure addresses to allow one for each PC and one for the Cisco IP phone.

Voice VLAN is supported only on access ports and not on trunk ports.

When you enter a maximum secure address value for an interface, if the new value is greater than the previous value, the new value overrides the previously configured value. If the new value is less than the previous value and the number of configured secure addresses on the interface exceeds the new value, the command is rejected.

The switch does not support port security aging of sticky secure MAC addresses.

A security violation occurs when the maximum number of secure MAC addresses are in the address table and a station whose MAC address is not in the address table attempts to access the interface or when a station whose MAC address is configured as a secure MAC address on another secure port attempts to access the interface.

When a secure port is in the error-disabled state, you can bring it out of this state by entering the errdisable recovery cause psecure-violation global configuration command. You can manually re-enable the port by entering the shutdown and no shut down interface configuration commands or by using the clear errdisable interface privileged EXEC command.

Setting a maximum number of addresses to one and configuring the MAC address of an attached device ensures that the device has the full bandwidth of the port.

When you enter a maximum secure address value for an interface, this occurs:

If the new value is greater than the previous value, the new value overrides the previously configured value.

If the new value is less than the previous value and the number of configured secure addresses on the interface exceeds the new value, the command is rejected.

Sticky secure MAC addresses have these characteristics:

When you enable sticky learning on an interface by using the switchport port-security mac-address sticky interface configuration command, the interface converts all the dynamic secure MAC addresses, including those that were dynamically learned before sticky learning was enabled, to sticky secure MAC addresses and adds all sticky secure MAC addresses to the running configuration.

If you disable sticky learning by using the no switchport port-security mac-address sticky interface configuration command or the running configuration is removed, the sticky secure MAC addresses remain part of the running configuration but are removed from the address table. The addresses that were removed can be dynamically reconfigured and added to the address table as dynamic addresses.

When you configure sticky secure MAC addresses by using the switchport port-security mac-address sticky mac-address interface configuration command, these addresses are added to the address table and the running configuration. If port security is disabled, the sticky secure MAC addresses remain in the running configuration.

If you save the sticky secure MAC addresses in the configuration file, when the switch restarts or the interface shuts down, the interface does not need to relearn these addresses. If you do not save the sticky secure addresses, they are lost. If sticky learning is disabled, the sticky secure MAC addresses are converted to dynamic secure addresses and are removed from the running configuration.

If you disable sticky learning and enter the switchport port-security mac-address sticky mac-address interface configuration command, an error message appears, and the sticky secure MAC address is not added to the running configuration.

Examples

This example shows how to enable port security on a port and to set the maximum number of secure addresses to 5. The violation mode is the default, and no secure MAC addresses are configured.

Switch(config)# interface gigabitethernet 0/2
Switch(config-if)# switchport mode access
Switch(config-if)# switchport port-security
Switch(config-if)# switchport port-security maximum 5

This example shows how to configure a secure MAC address and a VLAN ID on a port:

Switch(config)# interface gigabitethernet 0/2
Switch(config-if)# switchport mode trunk
Switch(config-if)# switchport port-security
Switch(config-if)# switchport port-security mac-address 1000.2000.3000 vlan 3

This example shows how to enable sticky learning and to enter two sticky secure MAC addresses on a port:

Switch(config)# interface gigabitethernet 0/2
Switch(config-if)# switchport port-security mac-address sticky 
Switch(config-if)# switchport port-security mac-address sticky 0000.0000.4141
Switch(config-if)# switchport port-security mac-address sticky 0000.0000.000f

This example show how to configure a port to shut down only the VLAN if a violation occurs:

Switch(config)# interface gigabitethernet 0/2
Switch(config)# switchport port-security violation shutdown vlan

You can verify your settings by using the show port-security privileged EXEC command.

Related Commands

Command
Description

clear port-security

Deletes from the MAC address table a specific type of secure address or all the secure addresses on the switch or an interface.

show port-security address

Displays all the secure addresses configured on the switch.

show port-security
interface
interface-id

Displays port security configuration for the switch or for the specified interface.


switchport port-security aging

Use the switchport port-security aging interface configuration command to set the aging time and type for secure address entries or to change the aging behavior for secure addresses on a particular port. Use the no form of this command to disable port security aging or to set the parameters to their default states.

switchport port-security aging {static | time time | type {absolute | inactivity}}

no switchport port-security aging {static | time | type}

Syntax Description

static

Enable aging for statically configured secure addresses on this port.

time time

Specify the aging time for this port. The range is 0 to 1440 minutes. If the time is 0, aging is disabled for this port.

type

Set the aging type.

absolute

Set absolute aging type. All the secure addresses on this port age out exactly after the time (minutes) specified and are removed from the secure address list.

inactivity

Set the inactivity aging type. The secure addresses on this port age out only if there is no data traffic from the secure source address for the specified time period.


Defaults

The port security aging feature is disabled. The default time is 0 minutes.

The default aging type is absolute.

The default static aging behavior is disabled.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

To enable secure address aging for a particular port, set the aging time to a value other than 0 for that port.

To allow limited time access to particular secure addresses, set the aging type as absolute. When the aging time lapses, the secure addresses are deleted.

To allow continuous access to a limited number of secure addresses, set the aging type as inactivity. This removes the secure address when it become inactive, and other addresses can become secure.

To allow unlimited access to a secure address, configure it as a secure address, and disable aging for the statically configured secure address by using the no switchport port-security aging static interface configuration command.

Examples

This example sets the aging time as 2 hours for absolute aging for all the secure addresses on the port:

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# switchport port-security aging time 120

This example sets the aging time as 2 minutes for inactivity aging type with aging enabled for configured secure addresses on the port:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport port-security aging time 2 
Switch(config-if)# switchport port-security aging type inactivity 
Switch(config-if)# switchport port-security aging static

This example shows how to disable aging for configured secure addresses:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# no switchport port-security aging static

Related Commands

Command
Description

show port-security

Displays the port security settings defined for the port.

switchport port-security

Enables port security on a port, restricts the use of the port to a user-defined group of stations, and configures secure MAC addresses.


switchport priority extend

Use the switchport priority extend interface configuration command to set a port priority for the incoming untagged frames or the priority of frames received by the IP phone connected to the specified port. Use the no form of this command to return to the default setting.

switchport priority extend {cos value | trust}

no switchport priority extend


Note To use this command, the switch must be running the LAN Base image.


Syntax Description

cos value

Set the IP phone port to override the IEEE 802.1p priority received from the PC or the attached device with the specified class of service (CoS) value. The range is 0 to 7. Seven is the highest priority. The default is 0.

trust

Set the IP phone port to trust the IEEE 802.1p priority received from the PC or the attached device.


Defaults

The default port priority is set to a CoS value of 0 for untagged frames received on the port.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

When voice VLAN is enabled, you can configure the switch to send the Cisco Discovery Protocol (CDP) packets to instruct the IP phone how to send data packets from the device attached to the access port on the Cisco IP Phone. You must enable CDP on the switch port connected to the Cisco IP Phone to send the configuration to the Cisco IP Phone. (CDP is enabled by default globally and on all switch interfaces.)

You should configure voice VLAN on switch access ports.

Before you enable voice VLAN, we recommend that you enable quality of service (QoS) on the switch by entering the mls qos global configuration command and configure the port trust state to trust by entering the mls qos trust cos interface configuration command.

Examples

This example shows how to configure the IP phone connected to the specified port to trust the received IEEE 802.1p priority:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport priority extend trust

You can verify your settings by entering the show interfaces interface-id switchport privileged EXEC command.

Related Commands

Command
Description

show interfaces

Displays the administrative and operational status of a switching port.

switchport voice vlan {vlan-id | dot1p | none | untagged}

Configures the voice VLAN on the port.


switchport protected

Use the switchport protected interface configuration command to isolate unicast, multicast, and broadcast traffic at Layer 2 from other protected ports on the same switch. Use the no form of this command to disable protection on the port.

switchport protected

no switchport protected

Syntax Description

This command has no arguments or keywords.

Defaults

No protected port is defined. All ports are nonprotected.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

The switchport protection feature is local to the switch; communication between protected ports on the same switch is possible only through a Layer 3 device. To prevent communication between protected ports on different switches, you must configure the protected ports for unique VLANs on each switch and configure a trunk link between the switches. A protected port is different from a secure port.

A protected port does not forward any traffic (unicast, multicast, or broadcast) to any other port that is also a protected port. Data traffic cannot be forwarded between protected ports at Layer 2; only control traffic, such as PIM packets, is forwarded because these packets are processed by the CPU and forwarded in software. All data traffic passing between protected ports must be forwarded through a Layer 3 device.

Port monitoring does not work if both the monitor and monitored ports are protected ports.

Examples

This example shows how to enable a protected port on an interface:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport protected

You can verify your settings by entering the show interfaces interface-id switchport privileged EXEC command.

Syntax Description

Command
Description

show interfaces switchport

Displays the administrative and operational status of a switching port, including port blocking and port protection settings.

switchport block

Prevents unknown multicast or unicast traffic on the interface.


switchport trunk

Use the switchport trunk interface configuration command to set the trunk characteristics when the interface is in trunking mode. Use the no form of this command to reset a trunking characteristic to the default.

switchport trunk {allowed vlan vlan-list | native vlan vlan-id | pruning vlan vlan-list}

no switchport trunk {allowed vlan | native vlan | {pruning vlan}

Syntax Description

allowed vlan vlan-list

Set the list of allowed VLANs that can receive and send traffic on this interface in tagged format when in trunking mode. See the following vlan-list format. The none keyword is not valid. The default is all.

native vlan vlan-id

Set the native VLAN for sending and receiving untagged traffic when the interface is in IEEE 802.1Q trunking mode. The range is 1 to 4094.

pruning vlan vlan-list

Set the list of VLANs that are eligible for VTP pruning when in trunking mode. The all keyword is not valid.


The vlan-list format is all | none | [add | remove | except] vlan-atom [,vlan-atom...] where:

all specifies all VLANs from 1 to 4094. This keyword is not allowed on commands that do not permit all VLANs in the list to be set at the same time.

none means an empty list. This keyword is not allowed on commands that require certain VLANs to be set or at least one VLAN to be set.

add adds the defined list of VLANs to those currently set instead of replacing the list. Valid IDs are from 1 to 1005; extended-range VLANs (VLAN IDs greater than 1005) are valid in some cases.


Note You can add extended-range VLANs to the allowed VLAN list, but not to the pruning-eligible VLAN list.


Separate nonconsecutive VLAN IDs with a comma; use a hyphen to designate a range of IDs.

remove removes the defined list of VLANs from those currently set instead of replacing the list. Valid IDs are from 1 to 1005; extended-range VLAN IDs are valid in some cases.


Note You can remove extended-range VLANs from the allowed VLAN list, but you cannot remove them from the pruning-eligible list.


Separate nonconsecutive VLAN IDs with a comma; use a hyphen to designate a range of IDs.

except lists the VLANs that should be calculated by inverting the defined list of VLANs. (VLANs are added except the ones specified.) Valid IDs are from 1 to 1005. Separate nonconsecutive VLAN IDs with a comma; use a hyphen to designate a range of IDs.

vlan-atom is either a single VLAN number from 1 to 4094 or a continuous range of VLANs described by two VLAN numbers, the lesser one first, separated by a hyphen.

Defaults

VLAN 1 is the default native VLAN ID on the port.

The default for all VLAN lists is to include all VLANs.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

Native VLANs:

All untagged traffic received on an IEEE 802.1Q trunk port is forwarded with the native VLAN configured for the port.

If a packet has a VLAN ID that is the same as the sending-port native VLAN ID, the packet is sent without a tag; otherwise, the switch sends the packet with a tag.

The no form of the native vlan command resets the native mode VLAN to the appropriate default VLAN for the device.

Allowed VLAN:

To reduce the risk of spanning-tree loops or storms, you can disable VLAN 1 on any individual VLAN trunk port by removing VLAN 1 from the allowed list. When you remove VLAN 1 from a trunk port, the interface continues to send and receive management traffic, for example, Cisco Discovery Protocol (CDP), Port Aggregation Protocol (PAgP), Link Aggregation Control Protocol (LACP), Dynamic Trunking Protocol (DTP), and VLAN Trunking Protocol (VTP) in VLAN 1.

The no form of the allowed vlan command resets the list to the default list, which allows all VLANs.

Trunk pruning:

The pruning-eligible list applies only to trunk ports.

Each trunk port has its own eligibility list.

If you do not want a VLAN to be pruned, remove it from the pruning-eligible list. VLANs that are pruning-ineligible receive flooded traffic.

VLAN 1, VLANs 1002 to 1005, and extended-range VLANs (VLANs 1006 to 4094) cannot be pruned.

Examples

This example shows how to configure VLAN 3 as the default for the port to send all untagged traffic:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport trunk native vlan 3

This example shows how to add VLANs 1, 2, 5, and 6 to the allowed list:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport trunk allowed vlan add 1,2,5,6

This example shows how to remove VLANs 3 and 10 to 15 from the pruning-eligible list:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport trunk pruning vlan remove 3,10-15

You can verify your settings by entering the show interfaces interface-id switchport privileged EXEC command.

Related Commands

Command
Description

show interfaces switchport

Displays the administrative and operational status of a switching port, including port blocking and port protection settings.

switchport mode

Configures the VLAN membership mode of a port.


switchport voice vlan

Use the switchport voice vlan interface configuration command to configure voice VLAN on the port. Use the no form of this command to return to the default setting.

switchport voice vlan {vlan-id | dot1p | none | untagged}

no switchport voice vlan

Syntax Description

vlan-id

Specify the VLAN to be used for voice traffic. The range is 1 to 4094. By default, the IP phone forwards the voice traffic with an IEEE 802.1Q priority of 5.

dot1p

Configure the telephone to use IEEE 802.1p priority tagging and uses VLAN 0 (the native VLAN). By default, the Cisco IP phone forwards the voice traffic with an IEEE 802.1p priority of 5.

none

Do not instruct the IP telephone about the voice VLAN. The telephone uses the configuration from the telephone key pad.

untagged

Configure the telephone to send untagged voice traffic. This is the default for the telephone.


Defaults

The switch default is not to automatically configure the telephone (none).

The telephone default is not to tag frames.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

You should configure voice VLAN on Layer 2 access ports.

You must enable Cisco Discovery Protocol (CDP) on the switchport connected to the Cisco IP phone for the switch to send configuration information to the phone. CDP is enabled by default globally and on the interface.

Before you enable voice VLAN, we recommend that you enable quality of service (QoS) on the switch by entering the mls qos global configuration command and configure the port trust state to trust by entering the mls qos trust cos interface configuration command.

When you enter a VLAN ID, the IP phone forwards voice traffic in IEEE 802.1Q frames, tagged with the specified VLAN ID. The switch puts IEEE 802.1Q voice traffic in the voice VLAN.

When you select dot1q, none, or untagged, the switch puts the indicated voice traffic in the access VLAN.

In all configurations, the voice traffic carries a Layer 2 IP precedence value. The default is 5 for voice traffic.

When you enable port security on an interface that is also configured with a voice VLAN, set the maximum allowed secure addresses on the port to two. When the port is connected to a Cisco IP phone, the IP phone requires one MAC address. The Cisco IP phone address is learned on the voice VLAN, but is not learned on the access VLAN. If you connect a single PC to the Cisco IP phone, no additional MAC addresses are required. If you connect more than one PC to the Cisco IP phone, you must configure enough secure addresses to allow one for each PC and one for the Cisco IP phone.

If any type of port security is enabled on the access VLAN, dynamic port security is automatically enabled on the voice VLAN.

You cannot configure static secure MAC addresses in the voice VLAN.

The Port Fast feature is automatically enabled when voice VLAN is configured. When you disable voice VLAN, the Port Fast feature is not automatically disabled.

Examples

This example shows how to configure VLAN 2 as the voice VLAN for the port:

Switch(config)# interface gigabitethernet0/2
Switch(config-if)# switchport voice vlan 2

You can verify your settings by entering the show interfaces interface-id switchport privileged EXEC command.

Related Commands

Command
Description

show interfaces interface-id switchport

Displays the administrative and operational status of a switching port.

switchport priority extend

Decides how the device connected to the specified port handles priority traffic received on its incoming port.


system mtu

Use the system mtu global configuration command to set the maximum packet size or maximum transmission unit (MTU) size for Gigabit Ethernet portsor for Fast Ethernet (10/100) ports. Use the no form of this command to restore the global MTU value to its default value.

system mtu {bytes | jumbo bytes}

no system mtu

Syntax Description

bytes

Set the system MTU for ports that are set to 10 or 100 Mb/s. The range is 1500 to 1998 bytes. This is the maximum MTU received at 10/100-Mb/s Ethernet switch ports.

jumbo bytes

Set the system jumbo MTU for Gigabit Ethernet ports operating at 1000 Mb/s or greater. The range is 1500 to 9000 bytes. This is the maximum MTU received at the physical port for Gigabit Ethernet ports.


Defaults

The default MTU size for all ports is 1500 bytes.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

When you use this command to change the system MTU or jumbo MTU size, you must reset the switch before the new configuration takes effect.The system MTU setting is saved in the switch environmental variable in NVRAM and becomes effective when the switch reloads. The MTU settings you enter with the system mtu and system mtu jumbo commands are not saved in the switch IOS configuration file, even if you enter the copy running-config startup-config privileged EXEC command. Therefore, if you use TFTP to configure a new switch by using a backup configuration file and want the system MTU to be other than the default, you must explicitly configure the system mtu and system mtu jumbo settings on the new switch and then reload the switch.

Gigabit Ethernet ports operating at 1000 Mb/s are not affected by the system mtu command, and 10/100-Mb/s ports are not affected by the system mtu jumbo command.

If you enter a value that is outside the range for the specific type of switch, the value is not accepted.


Note The switch does not support setting the MTU on a per-interface basis.


The size of frames that can be received by the switch CPU is limited to 1998 bytes, regardless of the value entered with the system mtu command. Although forwarded or routed frames are usually not received by the CPU, some packets (for example, control traffic, SNMP, Telnet, and routing protocols) are sent to the CPU.

For example, if the system mtu value is 1998 bytes and the system mtu jumbo value is 5000 bytes, packets up to 5000 bytes can be received on interfaces operating at 1000 Mb/s. However, although a packet larger than 1998 bytes can be received on an interface operating at 1000 Mb/s, if its destination interface is operating at 10 or 100 Mb/s, the packet is dropped.

Examples

This example shows how to set the maximum jumbo packet size for Gigabit Ethernet ports operating at 1000 Mb/s or greater to 1800 bytes:

Switch(config)# system mtu jumbo 1800
Switch(config)# exit
Switch# reload

You can verify your setting by entering the show system mtu privileged EXEC command.

Related Commands

Command
Description

show system mtu

Displays the packet size set for Fast Ethernetand Gigabit Ethernet ports.


test cable-diagnostics tdr

Use the test cable-diagnostics tdr privileged EXEC command to run the Time Domain Reflector (TDR) feature on an interface.

test cable-diagnostics tdr interface interface-id

Syntax Description

interface-id

Specify the interface on which to run TDR.


Defaults

There is no default.

Command Modes

Privileged EXEC

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

TDR is supported only on 10/100 and 10/100/1000 copper Ethernet ports. It is not supported on SFP module ports. For more information about TDR, see the software configuration guide for this release.

After you run TDR by using the test cable-diagnostics tdr interface interface-id command, use the show cable-diagnostics tdr interface interface-id privileged EXEC command to display the results.

Examples

This example shows how to run TDR on an interface:

Switch# test cable-diagnostics tdr interface gigabitethernet0/2
TDR test started on interface Gi0/2
A TDR test can take a few seconds to run on an interface
Use 'show cable-diagnostics tdr' to read the TDR results.

If you enter the test cable-diagnostics tdr interface interface-id command on an interface that has a link status of up and a speed of 10 or 100 Mb/s, these messages appear:

Switch# test cable-diagnostics tdr interface gigabitethernet0/3
TDR test on Gi0/3 will affect link state and traffic
TDR test started on interface Gi0/3
A TDR test can take a few seconds to run on an interface
Use 'show cable-diagnostics tdr' to read the TDR results.

Related Commands

Command
Description

show cable-diagnostics tdr

Displays the TDR results.


traceroute mac

Use the traceroute mac privileged EXEC command to display the Layer 2 path taken by the packets from the specified source MAC address to the specified destination MAC address.

traceroute mac [interface interface-id] {source-mac-address} [interface interface-id] {destination-mac-address} [vlan vlan-id] [detail]

Syntax Description

interface interface-id

(Optional) Specify an interface on the source or destination switch.

source-mac-address

Specify the MAC address of the source switch in hexadecimal format.

destination-mac-address

Specify the MAC address of the destination switch in hexadecimal format.

vlan vlan-id

(Optional) Specify the VLAN on which to trace the Layer 2 path that the packets take from the source switch to the destination switch. Valid VLAN IDs are 1 to 4094.

detail

(Optional) Specify that detailed information appears.


Defaults

There is no default.

Command Modes

Privileged EXEC

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

For Layer 2 traceroute to function properly, Cisco Discovery Protocol (CDP) must be enabled on all the switches in the network. Do not disable CDP.

When the switch detects a device in the Layer 2 path that does not support Layer 2 traceroute, the switch continues to send Layer 2 trace queries and lets them time out.

The maximum number of hops identified in the path is ten.

Layer 2 traceroute supports only unicast traffic. If you specify a multicast source or destination MAC address, the physical path is not identified, and an error message appears.

The traceroute mac command output shows the Layer 2 path when the specified source and destination addresses belong to the same VLAN. If you specify source and destination addresses that belong to different VLANs, the Layer 2 path is not identified, and an error message appears.

If the source or destination MAC address belongs to multiple VLANs, you must specify the VLAN to which both the source and destination MAC addresses belong. If the VLAN is not specified, the path is not identified, and an error message appears.

The Layer 2 traceroute feature is not supported when multiple devices are attached to one port through hubs (for example, multiple CDP neighbors are detected on a port). When more than one CDP neighbor is detected on a port, the Layer 2 path is not identified, and an error message appears.

This feature is not supported in Token Ring VLANs.

Examples

This example shows how to display the Layer 2 path by specifying the source and destination MAC addresses:

Switch# traceroute mac 0000.0201.0601 0000.0201.0201
Source 0000.0201.0601 found on con6[switch_mmodel] (2.2.6.6)
con6 (2.2.6.6) :Gi0/1 => Gi0/3
con5                 (2.2.5.5        )  :    Gi0/3 => Gi0/1
con1                 (2.2.1.1        )  :    Gi0/1 => Gi0/2
con2                 (2.2.2.2        )  :    Gi0/2 => Gi0/1
Destination 0000.0201.0201 found on con2[WS-C3550-24] (2.2.2.2)
Layer 2 trace completed

This example shows how to display the Layer 2 path by using the detail keyword:

Switch# traceroute mac 0000.0201.0601 0000.0201.0201 detail
Source 0000.0201.0601 found on con6[switch_mmodel] (2.2.6.6)
con6 /switch_mmodel/ 2.2.6.6 :
        Gi0/2 [auto, auto] => Gi0/3 [auto, auto]
con5 / switch_mmodel / 2.2.5.5 :
        Fa0/3 [auto, auto] => Gi0/1 [auto, auto]
con1 / switch_mmodel / 2.2.1.1 :
        Gi0/1 [auto, auto] => Gi0/2 [auto, auto]
con2 /switch_mmodel / 2.2.2.2 :
        Gi0/2 [auto, auto] => Fa0/1 [auto, auto]
Destination 0000.0201.0201 found on con2[WS-C3550-24] (2.2.2.2)
Layer 2 trace completed.

This example shows how to display the Layer 2 path by specifying the interfaces on the source and destination switches:

Switch# traceroute mac interface fastethernet0/1 0000.0201.0601 interface fastethernet0/3 
0000.0201.0201
Source 0000.0201.0601 found on con6[switch_mmodel] (2.2.6.6)
con6 (2.2.6.6) :Gi0/1 => Gi0/3
con5                 (2.2.5.5        )  :    Gi0/3 => Gi0/1
con1                 (2.2.1.1        )  :    Gi0/1 => G0/2
con2                 (2.2.2.2        )  :    Gi0/2 => Gi0/1
Destination 0000.0201.0201 found on con2[WS-C3550-24] (2.2.2.2)
Layer 2 trace completed

This example shows the Layer 2 path when the switch is not connected to the source switch:

Switch# traceroute mac 0000.0201.0501 0000.0201.0201 detail
Source not directly connected, tracing source .....
Source 0000.0201.0501 found on con5[switch_mmodel] (2.2.5.5)
con5 / switch_mmodel / 2.2.5.5 :
        Gi0/1 [auto, auto] => Gi0/3 [auto, auto]
con1 / switch_mmodel / 2.2.1.1 :
        Gi0/1 [auto, auto] => Gi0/2 [auto, auto]
con2 / switch_mmodel / 2.2.2.2 :
        Gi0/2 [auto, auto] => Fa0/1 [auto, auto]
Destination 0000.0201.0201 found on con2[WS-C3550-24] (2.2.2.2)
Layer 2 trace completed.

This example shows the Layer 2 path when the switch cannot find the destination port for the source MAC address:

Switch# traceroute mac 0000.0011.1111 0000.0201.0201
Error:Source Mac address not found. 
Layer2 trace aborted.

This example shows the Layer 2 path when the source and destination devices are in different VLANs:

Switch# traceroute mac 0000.0201.0601 0000.0301.0201
Error:Source and destination macs are on different vlans. 
Layer2 trace aborted.

This example shows the Layer 2 path when the destination MAC address is a multicast address:

Switch# traceroute mac 0000.0201.0601 0100.0201.0201
Invalid destination mac address

This example shows the Layer 2 path when source and destination switches belong to multiple VLANs:

Switch# traceroute mac 0000.0201.0601 0000.0201.0201
Error:Mac found on multiple vlans.
Layer2 trace aborted.

Related Commands

Command
Description

traceroute mac ip

Displays the Layer 2 path taken by the packets from the specified source IP address or hostname to the specified destination IP address or hostname.


traceroute mac ip

Use the traceroute mac ip privileged EXEC command to display the Layer 2 path taken by the packets from the specified source IP address or hostname to the specified destination IP address or hostname.

traceroute mac ip {source-ip-address | source-hostname} {destination-ip-address | destination-hostname} [detail]

Syntax Description

source-ip-address

Specify the IP address of the source switch as a 32-bit quantity in dotted-decimal format.

destination-ip-address

Specify the IP address of the destination switch as a 32-bit quantity in dotted-decimal format.

source-hostname

Specify the IP hostname of the source switch.

destination-hostname

Specify the IP hostname of the destination switch.

detail

(Optional) Specify that detailed information appears.


Defaults

There is no default.

Command Modes

Privileged EXEC

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

For Layer 2 traceroute to function properly, Cisco Discovery Protocol (CDP) must be enabled on all the switches in the network. Do not disable CDP.

When the switch detects an device in the Layer 2 path that does not support Layer 2 traceroute, the switch continues to send Layer 2 trace queries and lets them time out.

The maximum number of hops identified in the path is ten.

The traceroute mac ip command output shows the Layer 2 path when the specified source and destination IP addresses are in the same subnet. When you specify the IP addresses, the switch uses Address Resolution Protocol (ARP) to associate the IP addresses with the corresponding MAC addresses and the VLAN IDs.

If an ARP entry exists for the specified IP address, the switch uses the associated MAC address and identifies the physical path.

If an ARP entry does not exist, the switch sends an ARP query and tries to resolve the IP address. The IP addresses must be in the same subnet. If the IP address is not resolved, the path is not identified, and an error message appears.

The Layer 2 traceroute feature is not supported when multiple devices are attached to one port through hubs (for example, multiple CDP neighbors are detected on a port). When more than one CDP neighbor is detected on a port, the Layer 2 path is not identified, and an error message appears.

This feature is not supported in Token Ring VLANs.

Examples

This example shows how to display the Layer 2 path by specifying the source and destination IP addresses and by using the detail keyword:

Switch# traceroute mac ip 2.2.66.66 2.2.22.22 detail
Translating IP to mac ..... 
2.2.66.66 => 0000.0201.0601
2.2.22.22 => 0000.0201.0201

Source 0000.0201.0601 found on con6[WS-C2950G-24-EI] (2.2.6.6)
con6 / switch_mmodel / 2.2.6.6 :
        Gi0/1 [auto, auto] => Gi0/3 [auto, auto]
con5 / switch_mmodel / 2.2.5.5 :
        Fa0/3 [auto, auto] => Gi0/1 [auto, auto]
con1 / switch_mmodel / 2.2.1.1 :
        Gi0/1 [auto, auto] => Gi0/2 [auto, auto]
con2 / switch_mmodel / 2.2.2.2 :
        Gi0/2 [auto, auto] => Fa0/1 [auto, auto]
Destination 0000.0201.0201 found on con2[WS-C3550-24] (2.2.2.2)
Layer 2 trace completed.

This example shows how to display the Layer 2 path by specifying the source and destination hostnames:

Switch# traceroute mac ip con6 con2
Translating IP to mac ..... 
2.2.66.66 => 0000.0201.0601
2.2.22.22 => 0000.0201.0201

Source 0000.0201.0601 found on con6
con6 (2.2.6.6) :Gi0/1 => Gi0/3
con5                 (2.2.5.5        )  :    Gi0/3 => Gi0/1
con1                 (2.2.1.1        )  :    Gi0/1 => Gi0/2
con2                 (2.2.2.2        )  :    Gi0/2 => Fa0/1
Destination 0000.0201.0201 found on con2
Layer 2 trace completed

This example shows the Layer 2 path when ARP cannot associate the source IP address with the corresponding MAC address:

Switch# traceroute mac ip 2.2.66.66 2.2.77.77
Arp failed for destination 2.2.77.77.
Layer2 trace aborted.

Related Commands

Command
Description

traceroute mac

Displays the Layer 2 path taken by the packets from the specified source MAC address to the specified destination MAC address.


trust

Use the trust policy-map class configuration command to define a trust state for traffic classified through the class policy-map configuration or the class-map global configuration command. Use the no form of this command to return to the default setting.

trust [cos | dscp | ip-precedence]

no trust [cos | dscp | ip-precedence]

Syntax Description

cos

(Optional) Classify an ingress packet by using the packet class of service (CoS) value. For an untagged packet, the port default CoS value is used.

dscp

(Optional) Classify an ingress packet by using the packet Differentiated Services Code Point (DSCP) values (most significant 6 bits of 8-bit service-type field). For a non-IP packet, the packet CoS value is used if the packet is tagged. If the packet is untagged, the default port CoS value is used to map CoS to DSCP.

ip-precedence

(Optional) Classify an ingress packet by using the packet IP-precedence value (most significant 3 bits of 8-bit service-type field). For a non-IP packet, the packet CoS value is used if the packet is tagged. If the packet is untagged, the port default CoS value is used to map CoS to DSCP.


Defaults

The action is not trusted. If no keyword is specified when the command is entered, the default is dscp.

Command Modes

Policy-map class configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

Use this command to distinguish the quality of service (QoS) trust behavior for certain traffic from other traffic. For example, incoming traffic with certain DSCP values can be trusted. You can configure a class map to match and trust the DSCP values in the incoming traffic.

Trust values set with this command supersede trust values set with the mls qos trust interface configuration command.

The trust command is mutually exclusive with set policy-map class configuration command within the same policy map.

If you specify trust cos, QoS uses the received or default port CoS value and the CoS-to-DSCP map to generate a DSCP value for the packet.

If you specify trust dscp, QoS uses the DSCP value from the ingress packet. For non-IP packets that are tagged, QoS uses the received CoS value; for non-IP packets that are untagged, QoS uses the default port CoS value. In either case, the DSCP value for the packet is derived from the CoS-to-DSCP map.

If you specify trust ip-precedence, QoS uses the IP precedence value from the ingress packet and the IP-precedence-to-DSCP map. For non-IP packets that are tagged, QoS uses the received CoS value; for non-IP packets that are untagged, QoS uses the default port CoS value. In either case, the DSCP for the packet is derived from the CoS-to-DSCP map.

To return to policy-map configuration mode, use the exit command. To return to privileged EXEC mode, use the end command.

Examples

This example shows how to define a port trust state to trust incoming DSCP values for traffic classified with class1:

Switch(config)# policy-map policy1
Switch(config-pmap)# class class1
Switch(config-pmap-c)# trust dscp
Switch(config-pmap-c)# police 1000000 20000 exceed-action policed-dscp-transmit
Switch(config-pmap-c)# exit

You can verify your settings by entering the show policy-map privileged EXEC command.

Related Commands

Command
Description

class

Defines a traffic classification match criteria (through the police, set, and trust policy-map class configuration commands) for the specified class-map name.

police

Defines a policer for classified traffic.

policy-map

Creates or modifies a policy map that can be attached to multiple ports to specify a service policy.

set

Classifies IP traffic by setting a DSCP or IP-precedence value in the packet.

show policy-map

Displays QoS policy maps.


udld

Use the udld global configuration command to enable aggressive or normal mode in the UniDirectional Link Detection (UDLD) and to set the configurable message timer time. Use the no form of the command to disable aggressive or normal mode UDLD on all fiber-optic ports.

udld {aggressive | enable | message time message-timer-interval}

no udld {aggressive | enable | message}

Syntax Description

aggressive

Enable UDLD in aggressive mode on all fiber-optic interfaces.

enable

Enable UDLD in normal mode on all fiber-optic interfaces.

message time message-timer-interval

Configure the period of time between UDLD probe messages on ports that are in the advertisement phase and are determined to be bidirectional. The range is 7 to 90 seconds.


Defaults

UDLD is disabled on all interfaces.

The message timer is set at 60 seconds.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

UDLD supports two modes of operation: normal (the default) and aggressive. In normal mode, UDLD detects unidirectional links due to misconnected interfaces on fiber-optic connections. In aggressive mode, UDLD also detects unidirectional links due to one-way traffic on fiber-optic and twisted-pair links and due to misconnected interfaces on fiber-optic links. For information about normal and aggressive modes, see the "Understanding UDLD" section in the software configuration guide for this release.

If you change the message time between probe packets, you are making a trade-off between the detection speed and the CPU load. By decreasing the time, you can make the detection-response faster but increase the load on the CPU.

This command affects fiber-optic interfaces only. Use the udld interface configuration command to enable UDLD on other interface types.

You can use these commands to reset an interface shut down by UDLD:

The udld reset privileged EXEC command to reset all interfaces shut down by UDLD

The shutdown and no shutdown interface configuration commands

The no udld enable global configuration command followed by the udld {aggressive | enable} global configuration command to re-enable UDLD globally

The no udld port interface configuration command followed by the udld port or udld port aggressive interface configuration command to re-enable UDLD on the specified interface

The errdisable recovery cause udld and errdisable recovery interval interval global configuration commands to automatically recover from the UDLD error-disabled state

Examples

This example shows how to enable UDLD on all fiber-optic interfaces:

Switch(config)# udld enable

You can verify your setting by entering the show udld privileged EXEC command.

Related Commands

Command
Description

show udld

Displays UDLD administrative and operational status for all ports or the specified port.

udld port

Enables UDLD on an individual interface or prevents a fiber-optic interface from being enabled by the udld global configuration command.

udld reset

Resets all interfaces shut down by UDLD and permits traffic to again pass through.


udld port

Use the udld port interface configuration command to enable the UniDirectional Link Detection (UDLD) on an individual interface or prevent a fiber-optic interface from being enabled by the udld global configuration command. Use the no form of this command to return to the udld global configuration command setting or to disable UDLD if entered for a nonfiber-optic port.

udld port [aggressive]

no udld port [aggressive]

Syntax Description

aggressive

Enable UDLD in aggressive mode on the specified interface.


Defaults

On fiber-optic interfaces, UDLD is not enabled, not in aggressive mode, and not disabled. For this reason, fiber-optic interfaces enable UDLD according to the state of the udld enable or udld aggressive global configuration command.

On nonfiber-optic interfaces, UDLD is disabled.

Command Modes

Interface configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

A UDLD-capable port cannot detect a unidirectional link if it is connected to a UDLD-incapable port of another switch.

UDLD supports two modes of operation: normal (the default) and aggressive. In normal mode, UDLD detects unidirectional links due to misconnected interfaces on fiber-optic connections. In aggressive mode, UDLD also detects unidirectional links due to one-way traffic on fiber-optic and twisted-pair links and due to misconnected interfaces on fiber-optic links. For information about normal and aggressive modes, see the "Configuring UDLD" chapter in the software configuration guide for this release.

To enable UDLD in normal mode, use the udld port interface configuration command. To enable UDLD in aggressive mode, use the udld port aggressive interface configuration command.

Use the no udld port command on fiber-optic ports to return control of UDLD to the udld enable global configuration command or to disable UDLD on nonfiber-optic ports.

Use the udld port aggressive command on fiber-optic ports to override the setting of the udld enable or udld aggressive global configuration command. Use the no form on fiber-optic ports to remove this setting and to return control of UDLD enabling to the udld global configuration command or to disable UDLD on nonfiber-optic ports.

You can use these commands to reset an interface shut down by UDLD:

The udld reset privileged EXEC command to reset all interfaces shut down by UDLD

The shutdown and no shutdown interface configuration commands

The no udld enable global configuration command followed by the udld {aggressive | enable} global configuration command to re-enable UDLD globally

The no udld port interface configuration command followed by the udld port or udld port aggressive interface configuration command to re-enable UDLD on the specified interface

The errdisable recovery cause udld and errdisable recovery interval interval global configuration commands to automatically recover from the UDLD error-disabled state

Examples

This example shows how to enable UDLD on an port:

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# udld port 

This example shows how to disable UDLD on a fiber-optic interface despite the setting of the udld global configuration command:

Switch(config)# interface gigabitethernet0/1
Switch(config-if)# no udld port

You can verify your settings by entering the show running-config or the show udld interface privileged EXEC command.

Related Commands

Command
Description

show running-config

Displays the running configuration on the switch. For syntax information, select Cisco IOS Configuration Fundamentals Command Reference, Release 12.2 > File Management Commands > Configuration File Management Commands.

show udld

Displays UDLD administrative and operational status for all ports or the specified port.

udld

Enables aggressive or normal mode in UDLD or sets the configurable message timer time.

udld reset

Resets all interfaces shut down by UDLD and permits traffic to again pass through.


udld reset

Use the udld reset privileged EXEC command to reset all interfaces disabled by the UniDirectional Link Detection (UDLD) and permit traffic to begin passing through them again (though other features, such as spanning tree, Port Aggregation Protocol (PAgP), and Dynamic Trunking Protocol (DTP) still have their normal effects, if enabled).

udld reset

Syntax Description

This command has no arguments or keywords.

Command Modes

Privileged EXEC

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

If the interface configuration is still enabled for UDLD, these ports begin to run UDLD again and are disabled for the same reason if the problem has not been corrected.

Examples

This example shows how to reset all interfaces disabled by UDLD:

Switch# udld reset
1 ports shutdown by UDLD were reset.

You can verify your setting by entering the show udld privileged EXEC command.

Related Commands

Command
Description

show running-config

Displays the running configuration on the switch. For syntax information, select Cisco IOS Configuration Fundamentals Command Reference, Release 12.2 > File Management Commands > Configuration File Management Commands.

show udld

Displays UDLD administrative and operational status for all ports or the specified port.

udld

Enables aggressive or normal mode in UDLD or sets the configurable message timer time.

udld port

Enables UDLD on an individual interface or prevents a fiber-optic interface from being enabled by the udld global configuration command.


vlan (global configuration)

Use the vlan global configuration command to add a VLAN and to enter the VLAN configuration mode. Use the no form of this command to delete the VLAN. Configuration information for normal-range VLANs (VLAN IDs 1 to 1005) is always saved in the VLAN database. When you are using (VLAN Trunking Protocol (VTP) version 3 or when VTP mode is transparent (VTP version 1 or 2), you can create extended-range VLANs (VLAN IDs greater than 1005). In VTP version 3, these VLANs are also saved in the VLAN database.

vlan vlan-id

no vlan vlan-id

Syntax Description

vlan-id

ID of the VLAN to be added and configured. For vlan-id, the range is 1 to 4094. You can enter a single VLAN ID, a series of VLAN IDs separated by commas, or a range of VLAN IDs separated by hyphens.


Defaults

This command has no default settings.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

You use the vlan vlan-id global configuration command to add normal-range VLANs (VLAN IDs 1 t0 1005) or extended-range VLANs (VLAN IDs 1006 to 4094). With VTP version 1 and version 2, before adding extended-range VLANs, you must use the vtp transparent global configuration command to put the switch in VTP transparent mode. With VTP version 1 and 2, extended-range VLANs are not learned by VTP and are not added to the VLAN database. When VTP mode is transparent, VTP mode and domain name and all VLAN configurations are saved in the running configuration, and you can save them in the switch startup configuration file.

VTP version 3 supports propagation of extended-range VLANs and you can create them in VTP server or client mode.

When you save the VLAN and VTP configurations in the startup configuration file and reboot the switch, the configuration is selected in these ways:

If both the VLAN database and the configuration file show the VTP mode as transparent and the VTP domain names match, the VLAN database is ignored. The VTP and VLAN configurations in the startup configuration file are used. The VLAN database revision number remains unchanged in the VLAN database.

If the VTP mode is server, or if the startup VTP mode or domain names do not match the VLAN database, the VTP mode and the VLAN configuration for the first 1005 VLANs use the VLAN database information. With VTP version 3, all VLAN-IDs are in the VLAN database.

With VTP version 1 and version 2, if you try to create an extended-range VLAN when the switch is not in VTP transparent mode, the VLAN is rejected, and you receive an error message.

If you enter an invalid VLAN ID, you receive an error message and do not enter config-vlan mode.

Entering the vlan command with a VLAN ID enables config-vlan mode. When you enter the VLAN ID of an existing VLAN, you do not create a new VLAN, but you can modify VLAN parameters for that VLAN. The specified VLANs are added or modified when you exit the config-vlan mode. Only the shutdown command (for VLANs 1 to 1005) takes effect immediately.

These configuration commands are available in config-vlan mode. The no form of each command returns the characteristic to its default state.


Note Although all commands are visible, the only VLAN configuration commands that are supported on extended-range VLANs are mtu mtu-size and remote-span. For extended-range VLANs, all other characteristics must remain at the default state.


are are-number: defines the maximum number of all-routes explorer (ARE) hops for this VLAN. This keyword applies only to TrCRF VLANs.The range is 0 to 13. The default is 7. If no value is entered, 0 is assumed to be the maximum.

backupcrf: specifies the backup CRF mode. This keyword applies only to TrCRF VLANs.

enable backup CRF mode for this VLAN.

disable backup CRF mode for this VLAN (the default).

bridge {bridge-number| type}: specifies the logical distributed source-routing bridge, the bridge that interconnects all logical rings having this VLAN as a parent VLAN in FDDI-NET, Token Ring-NET, and TrBRF VLANs. The range is 0 to 15. The default bridge number is 0 (no source-routing bridge) for FDDI-NET, TrBRF, and Token Ring-NET VLANs. The type keyword applies only to TrCRF VLANs and is one of these:

srb (source-route bridging)

srt (source-route transparent) bridging VLAN

exit: applies changes, increments the VLAN database revision number (VLANs 1 to 1005 only), and exits config-vlan mode.

media: defines the VLAN media type. See Table 2-40 for valid commands and syntax for different media types.


Note The switch supports only Ethernet ports. You configure only FDDI and Token Ring media-specific characteristics for VLAN Trunking Protocol (VTP) global advertisements to other switches. These VLANs are locally suspended.


ethernet is Ethernet media type (the default).

fddi is FDDI media type.

fd-net is FDDI network entity title (NET) media type.

tokenring is Token Ring media type if the VTP v2 mode is disabled, or TrCRF if the VTP Version 2 (v) mode is enabled.

tr-net is Token Ring network entity title (NET) media type if the VTP v2 mode is disabled or TrBRF media type if the VTP v2 mode is enabled.

mtu mtu-size: specifies the maximum transmission unit (MTU) (packet size in bytes). The range is 1500 to 18190. The default is 1500 bytes.

name vlan-name: names the VLAN with an ASCII string from 1 to 32 characters that must be unique within the administrative domain. The default is VLANxxxx where xxxx represents four numeric digits (including leading zeros) equal to the VLAN ID number.

no: negates a command or returns it to the default setting.

parent parent-vlan-id: specifies the parent VLAN of an existing FDDI, Token Ring, or TrCRF VLAN. This parameter identifies the TrBRF to which a TrCRF belongs and is required when defining a TrCRF. The range is 0 to 1005. The default parent VLAN ID is 0 (no parent VLAN) for FDDI and Token Ring VLANs. For both Token Ring and TrCRF VLANs, the parent VLAN ID must already exist in the database and be associated with a Token Ring-NET or TrBRF VLAN.

remote-span: configure the VLAN as a Remote SPAN (RSPAN) VLAN. When the RSPAN feature is added to an existing VLAN, the VLAN is first deleted and is then recreated with the RSPAN feature. Any access ports are deactivated until the RSPAN feature is removed. If VTP is enabled, the new RSPAN VLAN is propagated by VTP for VLAN-IDs that are lower than 1024. Learning is disabled on the VLAN. See the remote-span command for more information.

ring ring-number: defines the logical ring for an FDDI, Token Ring, or TrCRF VLAN. The range is 1 to 4095. The default for Token Ring VLANs is 0. For FDDI VLANs, there is no default.

said said-value: specifies the security association identifier (SAID) as documented in IEEE 802.10. The range is 1 to 4294967294, and the number must be unique within the administrative domain. The default value is 100000 plus the VLAN ID number.

shutdown: shuts down VLAN switching on the VLAN. This command takes effect immediately. Other commands take effect when you exit config-vlan mode.

state: specifies the VLAN state:

active means the VLAN is operational (the default).

suspend means the VLAN is suspended. Suspended VLANs do not pass packets.

ste ste-number: defines the maximum number of spanning-tree explorer (STE) hops. This keyword applies only to TrCRF VLANs. The range is 0 to 13. The default is 7.

stp type: defines the spanning-tree type for FDDI-NET, Token Ring-NET, or TrBRF VLANs. For FDDI-NET VLANs, the default STP type is ieee. For Token Ring-NET VLANs, the default STP type is ibm. For FDDI and Token Ring VLANs, the default is no type specified.

ieee for IEEE Ethernet STP running source-route transparent (SRT) bridging.

ibm for IBM STP running source-route bridging (SRB).

auto for STP running a combination of source-route transparent bridging (IEEE) and source-route bridging (IBM).

tb-vlan1 tb-vlan1-id and tb-vlan2 tb-vlan2-id: specifies the first and second VLAN to which this VLAN is translationally bridged. Translational VLANs translate FDDI or Token Ring to Ethernet, for example. The range is 0 to 1005. If no value is specified, 0 (no transitional bridging) is assumed.

Table 2-40 Valid Commands and Syntax for Different Media Types 

Media Type
Valid Syntax

Ethernet

name vlan-name, media ethernet, state {suspend | active}, said said-value, mtu mtu-size, remote-span, tb-vlan1 tb-vlan1-id, tb-vlan2 tb-vlan2-id

FDDI

name vlan-name, media fddi, state {suspend | active}, said said-value, mtu mtu-size, ring ring-number, parent parent-vlan-id, tb-vlan1 tb-vlan1-id, tb-vlan2 tb-vlan2-id

FDDI-NET

name vlan-name, media fd-net, state {suspend | active}, said said-value, mtu  mtu-size, bridge bridge-number, stp type {ieee | ibm | auto}, tb-vlan1 tb-vlan1-id, tb-vlan2 tb-vlan2-id

If VTP v2 mode is disabled, do not set the stp type to auto.

Token Ring

VTP v1 mode is enabled.

name vlan-name, media tokenring, state {suspend | active}, said said-value, mtu mtu-size, ring ring-number, parent parent-vlan-id, tb-vlan1 tb-vlan1-id, tb-vlan2 tb-vlan2-id

Token Ring concentrator relay function (TrCRF)

VTP v2 mode is enabled.

name vlan-name, media tokenring, state {suspend | active}, said said-value, mtu mtu-size, ring ring-number, parent parent-vlan-id, bridge type {srb | srt}, are are-number, ste ste-number, backupcrf {enable | disable}, tb-vlan1 tb-vlan1-id, tb-vlan2 tb-vlan2-id

Token Ring-NET

VTP v1 mode is enabled.

name vlan-name, media tr-net, state {suspend | active}, said said-value, mtu mtu-size, bridge bridge-number, stp type {ieee | ibm}, tb-vlan1 tb-vlan1-id, tb-vlan2 tb-vlan2-id

Token Ring bridge relay function (TrBRF)

VTP v2 mode is enabled.

name vlan-name, media tr-net, state {suspend | active}, said said-value, mtu mtu-size, bridge bridge-number, stp type {ieee | ibm | auto}, tb-vlan1 tb-vlan1-id, tb-vlan2 tb-vlan2-id


Table 2-41 describes the rules for configuring VLANs.

Table 2-41 VLAN Configuration Rules 

Configuration
Rule

VTP v2 mode is enabled, and you are configuring a TrCRF VLAN media type.

Specify a parent VLAN ID of a TrBRF that already exists in the database.

Specify a ring number. Do not leave this field blank.

Specify unique ring numbers when TrCRF VLANs have the same parent VLAN ID. Only one backup concentrator relay function (CRF) can be enabled.

VTP v2 mode is enabled, and you are configuring VLANs other than TrCRF media type.

Do not specify a backup CRF.

VTP v2 mode is enabled, and you are configuring a TrBRF VLAN media type.

Specify a bridge number. Do not leave this field blank.

VTP v1 mode is enabled.

No VLAN can have an STP type set to auto.

This rule applies to Ethernet, FDDI, FDDI-NET, Token Ring, and Token Ring-NET VLANs.

Add a VLAN that requires translational bridging (values are not set to zero).

The translational bridging VLAN IDs that are used must already exist in the database.

The translational bridging VLAN IDs that a configuration points to must also contain a pointer to the original VLAN in one of the translational bridging parameters (for example, Ethernet points to FDDI, and FDDI points to Ethernet).

The translational bridging VLAN IDs that a configuration points to must be different media types than the original VLAN (for example, Ethernet can point to Token Ring).

If both translational bridging VLAN IDs are configured, these VLANs must be different media types (for example, Ethernet can point to FDDI and Token Ring).


Examples

This example shows how to add an Ethernet VLAN with default media characteristics. The default includes a vlan-name of VLANxxx, where xxxx represents four numeric digits (including leading zeros) equal to the VLAN ID number. The default media option is ethernet; the state option is active. The default said-value variable is 100000 plus the VLAN ID; the mtu-size variable is 1500; the stp-type option is ieee. When you enter the exit config-vlan configuration command, the VLAN is added if it did not already exist; otherwise, this command does nothing.

This example shows how to create a new VLAN with all default characteristics and enter config-vlan mode:

Switch(config)# vlan 200
Switch(config-vlan)# exit
Switch(config)#

This example shows how to create a new extended-range VLAN with all the default characteristics, to enter config-vlan mode, and to save the new VLAN in the switch startup configuration file:

Switch(config)# vtp mode transparent
Switch(config)# vlan 2000
Switch(config-vlan)# end
Switch# copy running-config startup config

You can verify your setting by entering the show vlan privileged EXEC command.

Related Commands

Command
Description

show vlan

Displays the parameters for all configured VLANs or one VLAN (if the VLAN ID or name is specified) in the administrative domain.


vlan (VLAN configuration)

This command is no longer supported.

Use the vlan VLAN configuration command to configure VLAN characteristics for a normal-range VLAN (VLAN IDs 1 to 1005) in the VLAN database. You access VLAN configuration mode by entering the vlan database privileged EXEC command.

vlan vlan-id [are are-number] [backupcrf {enable | disable}] [bridge bridge-number |
type {srb | srt}] [media {ethernet | fddi | fdi-net | tokenring | tr-net}] [mtu mtu-size]
[
name vlan-name] [parent parent-vlan-id] [ring ring-number] [said said-value]
[
state {suspend | active}] [ste ste-number] [stp type {ieee | ibm | auto}]
[
tb-vlan1 tb-vlan1-id] [tb-vlan2 tb-vlan2-id]

vlan database

This command is no longer supported.

Use the vlan database privileged EXEC command to enter VLAN configuration mode. From this mode, you can add, delete, and modify VLAN configurations for normal-range VLANs and globally propagate these changes by using the VLAN Trunking Protocol (VTP). Configuration information is saved in the VLAN database.

vlan database

vmps reconfirm (privileged EXEC)

Use the vmps reconfirm privileged EXEC command to immediately send VLAN Query Protocol (VQP) queries to reconfirm all dynamic VLAN assignments with the VLAN Membership Policy Server (VMPS).

vmps reconfirm

Syntax Description

This command has no arguments or keywords.

Defaults

No default is defined.

Command Modes

Privileged EXEC

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Examples

This example shows how to immediately send VQP queries to the VMPS:

Switch# vmps reconfirm

You can verify your setting by entering the show vmps privileged EXEC command and examining the VMPS Action row of the Reconfirmation Status section. The show vmps command shows the result of the last time the assignments were reconfirmed either because the reconfirmation timer expired or because the vmps reconfirm command was entered.

Related Commands

Command
Description

show vmps

Displays VQP and VMPS information.

vmps reconfirm (global configuration)

Changes the reconfirmation interval for the VQP client.


vmps reconfirm (global configuration)

Use the vmps reconfirm global configuration command to change the reconfirmation interval for the VLAN Query Protocol (VQP) client. Use the no form of this command to return to the default setting.

vmps reconfirm interval

no vmps reconfirm

Syntax Description

interval

Reconfirmation interval for VQP client queries to the VLAN Membership Policy Server (VMPS) to reconfirm dynamic VLAN assignments. The range is 1 to 120 minutes.


Defaults

The default reconfirmation interval is 60 minutes.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Examples

This example shows how to set the VQP client to reconfirm dynamic VLAN entries every 20 minutes:

Switch(config)# vmps reconfirm 20

You can verify your setting by entering the show vmps privileged EXEC command and examining information in the Reconfirm Interval row.

Related Commands

Command
Description

show vmps

Displays VQP and VMPS information.

vmps reconfirm (privileged EXEC)

Sends VQP queries to reconfirm all dynamic VLAN assignments with the VMPS.


vmps retry

Use the vmps retry global configuration command to configure the per-server retry count for the VLAN Query Protocol (VQP) client. Use the no form of this command to return to the default setting.

vmps retry count

no vmps retry

Syntax Description

count

Number of attempts to contact the VLAN Membership Policy Server (VMPS) by the client before querying the next server in the list. The range is 1 to 10.


Defaults

The default retry count is 3.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Examples

This example shows how to set the retry count to 7:

Switch(config)# vmps retry 7

You can verify your setting by entering the show vmps privileged EXEC command and examining information in the Server Retry Count row.

Related Commands

Command
Description

show vmps

Displays VQP and VMPS information.


vmps server

Use the vmps server global configuration command to configure the primary VLAN Membership Policy Server (VMPS) and up to three secondary servers. Use the no form of this command to remove a VMPS server.

vmps server ipaddress [primary]

no vmps server [ipaddress]

Syntax Description

ipaddress

IP address or hostname of the primary or secondary VMPS servers. If you specify a hostname, the Domain Name System (DNS) server must be configured.

primary

(Optional) Decides whether primary or secondary VMPS servers are being configured.


Defaults

No primary or secondary VMPS servers are defined.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.


Usage Guidelines

The first server entered is automatically selected as the primary server whether or not primary is entered. The first server address can be overridden by using primary in a subsequent command.

If a member switch in a cluster configuration does not have an IP address, the cluster does not use the VMPS server configured for that member switch. Instead, the cluster uses the VMPS server on the command switch, and the command switch proxies the VMPS requests. The VMPS server treats the cluster as a single switch and uses the IP address of the command switch to respond to requests.

When using the no form without specifying the ipaddress, all configured servers are deleted. If you delete all servers when dynamic-access ports are present, the switch cannot forward packets from new sources on these ports because it cannot query the VMPS.

Examples

This example shows how to configure the server with IP address 191.10.49.20 as the primary VMPS server. The servers with IP addresses 191.10.49.21 and 191.10.49.22 are configured as secondary servers:

Switch(config)# vmps server 191.10.49.20 primary
Switch(config)# vmps server 191.10.49.21
Switch(config)# vmps server 191.10.49.22

This example shows how to delete the server with IP address 191.10.49.21:

Switch(config)# no vmps server 191.10.49.21

You can verify your setting by entering the show vmps privileged EXEC command and examining information in the VMPS Domain Server row.

Related Commands

Command
Description

show vmps

Displays VQP and VMPS information.


vtp (global configuration)

Use the vtp global configuration command to set or modify the VLAN Trunking Protocol (VTP) configuration characteristics. Use the no form of this command to remove the settings or to return to the default settings.

vtp {domain domain-name | file filename | interface name [only] | mode {client | off | server | transparent} [mst | unknown | vlan] | password password [hidden | secret] | pruning | version number}

no vtp {file | interface | mode [client | off | server | transparent] [mst | unknown | vlan] | password | pruning | version}

Syntax Description

domain domain-name

Specify the VTP domain name, an ASCII string from 1 to 32 characters that identifies the VTP administrative domain for the switch. The domain name is case sensitive.

file filename

Specify the Cisco IOS file system file where the VTP VLAN configuration is stored.

interface name

Specify the name of the interface providing the VTP ID updated for this device.

only

(Optional) Use only the IP address of this interface as the VTP IP updater.

mode

Specify the VTP device mode as client, server, or transparent.

client

Place the switch in VTP client mode. A switch in VTP client mode is enabled for VTP, and can send advertisements, but does not have enough nonvolatile storage to store VLAN configurations. You cannot configure VLANs on the switch. When a VTP client starts up, it does not send VTP advertisements until it receives advertisements to initialize its VLAN database.

off

Place the switch in VTP off mode. A switch in off VTP off mode functions the same as a VTP transparent device except that it does not forward VTP advertisements on trunk ports.

server

Place the switch in VTP server mode. A switch in VTP server mode is enabled for VTP and sends advertisements. You can configure VLANs on the switch. The switch can recover all the VLAN information in the current VTP database from nonvolatile storage after reboot.

transparent

Place the switch in VTP transparent mode. A switch in VTP transparent mode is disabled for VTP, does not send advertisements or learn from advertisements sent by other devices, and cannot affect VLAN configurations on other devices in the network. The switch receives VTP advertisements and forwards them on all trunk ports except the one on which the advertisement was received.

When VTP mode is transparent, the mode and domain name are saved in the switch running configuration file, and you can save them in the switch startup configuration file by entering the copy running-config startup config privileged EXEC command.

mst

(Optional) Set the mode for the multiple spanning tree (MST) VTP database (only VTP version 3).

unknown

(Optional) Set the mode for unknown VTP databases (only VTP version 3).

vlan

(Optional) Set the mode for VLAN VTP database. This is the default (only VTP version 3).

password password

Set the administrative domain password for the generation of the 16-byte secret value used in MD5 digest calculation to be sent in VTP advertisements and to validate received VTP advertisements. The password can be an ASCII string from 1 to 32 characters. The password is case sensitive.

hidden

(Optional) Specify that the key generated from the password string is saved in the VLAN database file. When the hidden keyword is not specified, the password string is saved in clear text. When the hidden password is entered, you need to reenter the password to issue a command in the domain. This keyword is supported only in VTP version 3 .

secret

(Optional) Allow the user to directly configure the password secret key (only VTP version 3).

pruning

Enable VTP pruning on the switch.

version number

Set VTP version to version 1, version 2, or version 3.


Defaults

The default filename is flash:vlan.dat.

The default mode is server mode and the default database is VLAN.

In VTP version 3, for the MST database, the default mode is transparent.

No domain name or password is defined.

No password is configured.

Pruning is disabled.

The default version is Version 1.

Command Modes

Global configuration

Command History

Release
Modification

12.2(25)FX

This command was introduced.

12.2(52)SE

The mode off keyword was added, support was added for VTP version 3, and the password hidden and secret keywords and the mode database keywords (vlan, mst, and unknown) were added with VTP version 3.


Usage Guidelines

VTP version 3 is supported only when the switch is running the LAN base image.

When you save VTP mode, domain name, and VLAN configurations in the switch startup configuration file and reboot the switch, the VTP and VLAN configurations are selected by these conditions:

If both the VLAN database and the configuration file show the VTP mode as transparent and the VTP domain names match, the VLAN database is ignored. The VTP and VLAN configurations in the startup configuration file are used. The VLAN database revision number remains unchanged in the VLAN database.

If the startup VTP mode is server mode, or the startup VTP mode or domain names do not match the VLAN database, VTP mode and VLAN configuration for the first 1005 VLANs are selected by VLAN database information, and VLANs greater than 1005 are configured from the switch configuration file.

The vtp file filename cannot be used to load a new database; it renames only the file in which the existing database is stored.

Follow these guidelines when configuring a VTP domain name:

The switch is in the no-management-domain state until you configure a domain name. While in the no-management-domain state, the switch does not send any VTP advertisements even if changes occur to the local VLAN configuration. The switch leaves the no-management-domain state after it receives the first VTP summary packet on any port that is trunking or after you configure a domain name by using the vtp domain command. If the switch receives its domain from a summary packet, it resets its configuration revision number to 0. After the switch leaves the no-management-domain state, it can no be configured to re-enter it until you clear the NVRAM and reload the software.

Domain names are case-sensitive.

After you configure a domain name, it cannot be removed. You can only reassign it to a different domain.

Follow these guidelines when setting VTP mode:

The no vtp mode command returns the switch to VTP server mode.

The vtp mode server command is the same as no vtp mode except that it does not return an error if the switch is not in client or transparent mode.

If the receiving switch is in client mode, the client switch changes its configuration to duplicate the configuration of the server. If you have switches in client mode, be sure to make all VTP or VLAN configuration changes on a switch in server mode. If the receiving switch is in server mode or transparent mode, the switch configuration is not changed.

Switches in transparent mode do not participate in VTP. If you make VTP or VLAN configuration changes on a switch in transparent mode, the changes are not propagated to other switches in the network.

If you change the VTP or VLAN configuration on a switch that is in server mode, that change is propagated to all the switches in the same VTP domain.

The vtp mode transparent command disables VTP from the domain but does not remove the domain from the switch.

In VTP versions 1 and 2, the VTP mode must be transparent for you to add extended-range VLANs or for VTP and VLAN information to be saved in the running configuration file. VTP supports extended-range VLANs in client and server mode and saved them in the VLAN database.

With VTP versions 1 and 2, if extended-range VLANs are configured on the switch and you attempt to set the VTP mode to server or client, you receive an error message, and the configuration is not allowed. Changing VTP mode is allowed with extended VLANs in VTP version 3.

VTP can be set to either server or client mode only when dynamic VLAN creation is disabled.

The vtp mode off command sets the device to off. The no vtp mode off command resets the device to the VTP server mode.

Follow these guidelines when setting a VTP password:

Passwords are case sensitive. Passwords should match on all switches in the same domain.

When you use the no vtp password form of the command, the switch returns to the no-password state.

The hidden and secret keywords are supported only in VTP version 3. If you convert from VTP version 2 to VTP version 3, you must remove the hidden or secret keyword before the conversion.

Follow these guidelines when setting VTP pruning:

VTP pruning removes information about each pruning-eligible VLAN from VTP updates if there are no stations belonging to that VLAN.

If you enable pruning on the VTP server, it is enabled for the entire management domain for VLAN IDs 1 to 1005.

Only VLANs in the pruning-eligible list can be pruned.

Pruning is supported with VTP Version 1 and Version 2.

Follow these guidelines when setting the VTP version:

Toggling the Version 2 (v2) mode state modifies parameters of certain default VLANs.

Each VTP switch automatically detects the capabilities of all the other VTP devices. To use Version 2, all VTP switches in the network must support Version 2; otherwise, you must configure them to operate in VTP Version 1 mode.

If all switches in a domain are VTP Version 2-capable, you need only to configure Version 2 on one switch; the version number is then propagated to the other Version-2 capable switches in the VTP domain.

If you are using VTP in a Token Ring environment, VTP Version 2 must be enabled.

If you are configuring a Token Ring bridge relay function (TrBRF) or Token Ring concentrator relay function (TrCRF) VLAN media type, you must use Version 2.

If you are configuring a Token Ring or Token Ring-NET VLAN media type, you must use Version 1.

In VTP version 3, all database VTP information is propagated across the VTP domain, not only VLAN database information.

Two VTP version 3 regions can only communicate over a VTP version 1 or VTP version 2 region in transparent mode.

You cannot save password, pruning, and version configurations in the switch configuration file.

Examples

This example shows how to rename the filename for VTP configuration storage to vtpfilename:

Switch(config)# vtp file vtpfilename

This example shows how to clear the device storage filename:

Switch(config)# no vtp file vtpconfig
Clearing device storage filename.

This example shows how to specify the name of the interface providing the VTP updater ID for this device:

Switch(config)# vtp interface gigabitethernet

This example shows how to set the administrative domain for the switch:

Switch(config)# vtp domain OurDomainName

This example shows how to place the switch in VTP transparent mode:

Switch(config)# vtp mode transparent

This example shows how to configure the VTP domain password:

Switch(config)# vtp password ThisIsOurDomain'sPassword

This example shows how to enable pruning in the VLAN database:

Switch(config)# vtp pruning
Pruning switched ON

This example shows how to enable Version 2 mode in the VLAN database:

Switch(config)# vtp version 2

You can verify your settings by entering the show vtp status privileged EXEC command.

Related Commands

Command
Description

show vtp status

Displays the VTP statistics for the switch and general information about the VTP management domain status.

vtp (interface configuration)

Enables or disables VTP on an interface.


vtp (interface configuration)

Use the vtp interface configuration command to enable the VLAN Trunking Protocol (VTP) on a per-port basis. Use the no form of this command to disable VTP on the interface.

vtp

no vtp


Note This command is supported only when the switch is running the LAN base image and VTP version 3.


Syntax Description

This command has no keywords or arguments.

Command Default

This command has no default settings.

Command Modes

Interface configuration.

Command History

Release
Modification

12.2(52)SE

This command was introduced.


Usage Guidelines

Enter this command only interfaces that are switchport in trunk mode.

This command is supported only on switches configured for VTP version 3.

Examples

This example shows how to enable VTP on an interface:

Switch(config-if)# vtp

This example shows how to disable VTP on an interface:

Switch(config-if)# no vtp

Related Commands

Command
Description

vtp (global configuration)

Globally configures VTP domain-name, password, pruning, version, and mode.



vtp (VLAN configuration)

This command is no longer supported.

Use the vtp VLAN configuration command to configure VLAN Trunking Protocol (VTP) characteristics. You access VLAN configuration mode by entering the vlan database privileged EXEC command.

vtp {domain domain-name | password password | pruning | v2-mode | {server | client | transparent}}

no vtp {client | password | pruning | transparent | v2-mode}

vtp primary

Use the vtp primary privileged EXEC command to configure a switch as the VLAN Trunking Protocol (VTP) primary server.

vtp primary [mst | vlan] [force]

There is no no form of the command.


Note This command is supported only when the switch is running the LAN base image and VTP version 3.



Note Although visible in the command line help, the vtp {password password | pruning | version number} commands are not supported.


Syntax Description

mst

(Optional) Configure the switch as the primary VTP server for the multiple spanning tree (MST) feature.

vlan

(Optional) Configure the switch as the primary VTP server for VLANs .

force

(Optional) Configure the switch to not check for conflicting devices when configuring the primary server.


Defaults

The switch is a VTP secondary server.

Command Modes

Privileged EXEC

Command History

Release
Modification

12.2(52)SE

This command was introduced.


Usage Guidelines

This command is supported only on switches configured for VTP version 3.

A VTP primary server updates the database information and sends updates that are honored by all devices in the system. A VTP secondary server can only back up the updated VTP configurations received from the primary server to NVRAM.

By default, all devices come up as secondary servers. Primary server status is needed only for database updates when the administrator issues a takeover message in the domain. You can have a working VTP domain without any primary servers.

Primary server status is lost if the device reloads or domain parameters change.

Examples

This example shows how to configure the switch as the primary VTP server for VLANs:

Switch# vtp primary vlan
Setting device to VTP TRANSPARENT mode.

You can verify your settings by entering the show vtp status privileged EXEC command.

Related Commands

Command
Description

show vtp status

Displays the VTP statistics for the switch and general information about the VTP management domain status.

vtp (global configuration)

Configures the VTP filename, interface, domain name, mode, and version.