To display VLAN information, use the show vlan command in privileged EXEC mode.

Syntax Description

Command Modes

Privileged EXEC (#)

Command History

Usage Guidelines

Each Ethernet switch port and Ethernet repeater group belong to only one VLAN. Trunk ports can be on multiple VLANs.

If you shut down a VLAN using the state suspend or the state activecommand, these values appear in the Status field:

• suspended--VLAN is suspended.
• active--VLAN is active.

If you shut down a VLAN using the shutdown command, these values appear in the Status field:

• act/lshut--VLAN status is active but shut down locally.
• sus/lshut--VLAN status is suspended but shut down locally.

This is an example of the output for a VLAN (VLAN0002) that is active but shut down locally:

Router# show vlan
VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Fa5/9
2    VLAN0002                         act/lshut Fa5/9
<...Output truncated...>

If a VLAN is shut down internally, these values appear in the Status field:

• act/ishut--VLAN status is active but shut down internally.
• sus/ishut--VLAN status is suspended but shut down internally.

This is an example of the output for a VLAN (VLAN0002) that is active but shut down internally:

Router# show vlan
VLAN Name                             Status    Ports
---- -------------------------------- --------- -------------------------------
1    default                          active    Fa5/9
2    VLAN0002                         act/ishut Fa5/9
<...Output truncated...>

If a VLAN is shut down locally and internally, the value that is displayed in the Status field is act/ishut or sus/ishut. If a VLAN is shut down locally only, the value that is displayed in the Status field is act/lshut or sus/lshut.

Separate VLAN ranges with a hyphen, and separate VLANs with a comma and no spaces in between. For example, you can enter the following:

Router# show vlan id 1-4,3,7,5-20

When displaying a single VLAN both trunk and non-trunk ports are displayed. A non-trunk port is a port that is not configured as pm_port_mode_trunk. If an interface is configured as "switchport port mode trunk" it is displayed whether the link is up or down.

When displaying multiple VLANs only non-trunk ports are displayed.

Related Commands

To display VLAN access control list (VACL) logging configuration properties, use the showvlanaccess-logconfigcommand in privileged EXEC mode.

Syntax Description

This command has no arguments or keywords.

Command Modes

Privileged EXEC (#)

Command History

Usage Guidelines

Syslog messages are generated when the device reaches the set threshold, or five minutes after the previous message is displayed, whichever occurs first. The threshold controls the rate of the syslog message only and does not affect the log table entries. Packets exceeding the specified rate limit will not be logged.

Related Commands

To display VLAN access control list (VACL) flow table contents, use the showvlanaccess-logflowcommand in privileged EXEC mode.

Syntax Description

Command Modes

Privileged EXEC (#)

Command History

Usage Guidelines

Entries for the standard protocols or any protocol can be displayed by specifying the protocol name or protocol number. Entries are removed from the table, if there is no increment in the packet counter after the last syslog message.

Related Commands

To display VLAN access control list (VACL) packet counts, messages, and other statistics, use the showvlanaccess-logstatisticscommand in privileged EXEC mode.

Syntax Description

This command has no arguments or keywords.

Command Modes

Privileged EXEC (#)

Command History

Usage Guidelines

All platforms do not display VACL logging index. Packets that are dropped do not generate any syslog messages.

Related Commands

To display the contents of a VLAN-access map, use the showvlanaccess-map command in privileged EXEC mode.

Syntax Description

Command Modes

Privileged EXEC (#)

Command History

Related Commands

To display VLAN information for trunk and access ports, use theshowvlanall-ports command in privileged EXEC mode.

Syntax Description

This command has no arguments or keywords.

Command Modes

Privileged EXEC (#)

Command History

To display the software-cached counter values, use the showvlancounters command in privileged EXEC mode.

Syntax Description

Command Modes

Privileged EXEC (#)

Command History

Usage Guidelines

The showvlanidcounters command is not supported on switch virtual interfaces (SVIs).

For Layer 2 and Layer 3 VLAN interfaces and router ports, per-interface switching statistics and VLAN-counter information to the Multilayer Switching Feature Card 2 (MSFC2) are exported approximately every 3 minutes.

If you enter the showvlancounters command with no arguments, the software-cached counter values for all VLANs are displayed.

Related Commands

To display native VLAN-tagging information, use the showvlandot1qtagnative command in privileged EXEC mode.

Syntax Description

This command has no arguments or keywords.

Command Modes

Privileged EXEC (#)

Command History

Related Commands

To display information about the VLAN filter, use the showvlanfilter command in privileged EXEC mode.

Syntax Description

Command Modes

Privileged EXEC (#)

Command History

Usage Guidelines

The showvlanfiltermap-nameinterface command accepts only ATM, packet over SONET/SDH (POS), or serial interface types. If your system is not configured with any of these interface types, the interfaceinterfaceinterface-number keyword and arguments are not provided.

The interface-number argument designates the module and port number. Valid values for interface-number depend on the specified interface type and the chassis and module that are used. For example, if you specify a Gigabit Ethernet interface and have a 48-port 10/100BASE-T Ethernet module that is installed in a 13-slot chassis, valid values for the module number are from 2 to 13 and valid values for the port number are from 1 to 48.

If you do not specify an optional keyword and argument, all mappings are displayed. If you enter access-map map_name, all the VLANs and interfaces that are associated with the specified map are shown. If you enter vlan vlan-id or interfaceinterfaceinterface-number, its associated access map, if existing, is shown.

In the output for VLAN access control lists (VACLs) on VLANs, the following applies:

• Configured on VLANs--User configured
• Active on VLANs--VLAN list on which the VACL is active

In the WAN-interface outputs, the following applies:

• Configured on interfaces--User configured
• Active on Interfaces--Interfaces on which the VACL is active

Related Commands

To display the total number of free VLANs on a router, use the show vlan free command in privileged EXEC mode .

Syntax Description

This command has no arguments or keywords.

Command Default

All free VLANs are displayed.

Command Modes

Privileged EXEC (#)

Usage Guidelines

Theshowvlanfree command displays the total number of free VLANs on a router.

Command History

Related Commands

To display the usage summary information for VLANs, use the showfreevlansummary command in privileged EXEC mode .

Syntax Description

This command has no arguments or keywords.

Command Default

Usage summary information for all of the free VLANs is displayed.

Command Modes

Privileged EXEC (#)

Usage Guidelines

Theshowvlanfreesummarycommand displays the following VLAN information:

• Total number of available VLANs
• Total number of free VLANs
• Total number of used VLANs.

Command History

Related Commands

To display information about the internal VLAN allocation, use the showvlaninternalusage command in privileged EXEC mode.

Syntax Description

Command Modes

Privileged EXEC (#)

Command History

Usage Guidelines

In some cases, the output displays the following:

workaround vlan

A workaround VLAN is used to enable the Policy Feature Card (PFC)-based policing on the PWAN1 main interface. Without the workaround VLAN, the packets hit the PFC policer twice for PWAN1 because the same VLAN is used when packets traverse the local bus before and after Parallel eXpress Forwarding (PXF) processing.

Entering the showvlaninternalusage command displays the Optical Services Module (OSM) interfaces and subinterfaces in addition to the regular Ethernet interfaces.

To display the associated subinterfaces, enter the showcwanvlan command. The showcwanvlan command displays the mapping between the WAN subinterface and the internal VLANs in use.

To register a mapping of an 802.1Q VLAN to an Inter-Switch Link (ISL) VLAN, use the showvlanmapping command in privileged EXEC mode.

Syntax Description

This command has no arguments or keywords.

Command Modes

Privileged EXEC (#)

Command History

Related Commands

To display the VLAN port provisioning status, use the showvlanportprovisioningcommand in privileged EXEC mode.

Syntax Description

This command has no arguments or keywords.

Command Modes

Command History

Related Commands

To display private VLAN (PVLAN) information, use the show vlan private-vlan command in privileged EXEC mode.

Syntax Description

Command Modes

Privileged EXEC (#)

Command History

Usage Guidelines

In the showvlanprivate-vlantype command output display, "normal" displayed as a type indicates a regular VLAN that is configured in a PVLAN. A display of "normal" means that two VLANs have been associated before the type was set and that the PVLAN is not operational. This information is useful for debugging purposes.

Related Commands

To display a list of remote Switched Port Analyzer (RSPAN) VLANs, use the showvlanremote-spancommand in privileged EXEC mode.

Syntax Description

This command has no arguments or keywords.

Command Modes

Privileged EXEC (#)

Command History

Related Commands

To display the number of logical virtual ports required, use the show vlan virtual-port command in privileged EXEC mode.

Syntax Description

Command Modes

Privileged EXEC (#)

Command History

To display the VLAN range, use the showvlan-range command in privileged EXEC mode.

Syntax Description

This command has no arguments or keywords.

Command Modes

Privileged EXEC (#)

Command History

Related Commands

To display statistics about 802.1Q VLAN subinterfaces, use the showvlansdot1q command in privileged EXEC mode.

Syntax Description

Command Modes

Privileged EXEC (#)

Command History

Usage Guidelines

If no arguments or keywords are entered, statistics for all of the 802.1Q VLAN IDs are displayed.

The any keyword is not supported for IPoQinQ because IP routing is not supported on ambiguous subinterfaces. However, the second-dot1q inner-id keyword and argument can be used on IPoQinQ for a specific inner VLAN ID that is not an ambiguous subinterface.

Note	On the Cisco 10000 series router, the following is an implementation limitation--when a service policy is applied to a PPPoEoQinQ or IPoQinQ subinterface and the service policy drops some packets, the packets dropped are still displayed in the outgoing packet counters as output.

Note	For the Cisco ASR 1000 Series Aggregation Services Router only, the command output includes the total number of packets dropped from the shared port adapter (SPA) because of ingress oversubscription on the VLAN. An example of the output is included in the section below.

Related Commands

To display Token Ring VLANs, use the showvlanstokenring command in user EXEC or privileged EXEC mode.

Syntax Description

This command has no arguments or keywords.

Command Modes

User EXEC (>) Privileged EXEC (#)

Command History

Related Commands

To display VLAN information, use the showvlan-switch command in user EXEC or privileged EXEC mode.

Syntax Description

Command Modes

User EXEC (>) Privileged EXEC (#)

Command History

Usage Guidelines

Each Ethernet switch port and Ethernet repeater group belongs to only one VLAN. Trunk ports can be on multiple VLANs.

Related Commands

To display general information about the VLAN Trunking Protocol (VTP) management domain, status, and counters, use theshowvtp command in privileged EXEC mode.

Syntax Description

Command Modes

Privileged EXEC (#)

Command History

Usage Guidelines

In the output of the showvtpstatus command, the last modified time is of the modifier itself. For example, the time displayed in the line "Configuration last modified by 7.0.22.11 at 5-5-06 05:51:49", is the time that the modifier (7.0.22.11) last modified the VLAN configuration.

Related Commands

To shut down local traffic on a specified VLAN, use the shutdownvlan command in global configuration mode. To restart local traffic on the VLAN, use the no form of this command.

Syntax Description

Command Default

Local traffic on a specified VLAN is not shut down.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

This command does not support extended-range VLANs.

To enable the Simple Network Management Protocol (SNMP) trap notification on a LAN port when MAC addresses are added to or removed from the address table , use the snmptrapmac-notificationchange command in interface configuration mode. To disable the SNMP trap notification on a LAN port when MAC addresses are added to or removed from the address table , use the no form of this command.

Syntax Description

Command Default

The SNMP trap notification is disabled.

Command Modes

Interface configuration (config-if)

Command History

Related Commands

To configure more than one WAN interface in a single Encapsulated Remote Switched Port Analyzer (ERSPAN) session, use the source interface command in ERSPAN monitor source session configuration mode.

Syntax Description

Command Modes

ERSPAN monitor source session configuration mode (config-mon-erspan-src)

Command History

Usage Guidelines

• When you configure multiple interfaces in a session, list each interface along with its port and interface number, and separate each interface using a comma.

• You can configure more than one WAN interface in a single ERSPAN source monitor session by separating different WAN interfaces using a comma. You can configure 20 WAN interfaces separated by a comma and an unlimited interfaces using hyphens.

• The Serial keyword is displayed only if a serial interface is configured on the router.

• If the Source interface Serial command is configured, you cannot configure the source vlan command under the same ERSPAN source monitor session.

• You cannot configure a virtual LAN (VLAN) in an ERSPAN monitoring session on a WAN interface.

Related Commands

To enable bridge protocol data unit (BPDU) filtering by default on all PortFast ports, use the spanning-treeportfastbpdufilterdefaultcommand in global configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

Disabled

Command Modes

Global configuration (config)

Command History

Usage Guidelines

The spanning-treeportfastbpdufilter command enables BPDU filtering globally on PortFast ports. BPDU filtering prevents a port from sending or receiving any BPDUs.

You can override the effects of the portfastbpdufilterdefault command by configuring BPDU filtering at the interface level.

Note

Be careful when enabling BPDU filtering. The feature's functionality is different when you enable it on a per-port basis or globally. When enabled globally, BPDU filtering is applied only on ports that are in an operational PortFast state. Ports send a few BPDUs at linkup before they effectively filter outbound BPDUs. If a BPDU is received on an edge port, it immediately loses its operational PortFast status and BPDU filtering is disabled. When enabled locally on a port, BPDU filtering prevents the Cisco 7600 series router from receiving or sending BPDUs on this port.

Caution

Be careful when using this command. Using this command incorrectly can cause bridging loops.

Related Commands

To enable BackboneFast to allow a blocked port on a switch to change immediately to a listening mode, use the spanning-treebackbonefast command in global configuration mode. To return to the default setting, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

BackboneFast is disabled.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

BackboneFast should be enabled on all of the Cisco routers containing an Ethernet switch network module. BackboneFast provides for fast convergence in the network backbone after a spanning-tree topology change. It enables the switch to detect an indirect link failure and to start the spanning-tree reconfiguration sooner than it would under normal spanning-tree rules.

Use the showspanning-tree privileged EXEC command to verify your settings.

Related Commands

To enable bridge protocol data unit (BPDU) filtering on the interface, use the spanning-treebpdufiltercommand in interface configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

Command Default

The setting that is already configured when you enter the spanning-treeportfastbpdufilterdefault command .

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

Caution

Be careful when you enter the spanning-treebpdufilterenable command. Enabling BPDU filtering on an interface is similar to disabling the spanning tree for this interface. If you do not use this command correctly, you might create bridging loops.

Entering the spanning-treebpdufilterenable command to enable BPDU filtering overrides the PortFast configuration.

When configuring Layer 2-protocol tunneling on all the service-provider edge switches, you must enable spanning-tree BPDU filtering on the 802.1Q tunnel ports by entering the spanning-treebpdufilterenable command.

BPDU filtering prevents a port from sending and receiving BPDUs. The configuration is applicable to the whole interface, whether it is trunking or not. This command has three states:

• spanning-tree bpdufilter enable -- Unconditionally enables BPDU filtering on the interface.
• spanning-tree bpdufilter disable -- Unconditionally disables BPDU filtering on the interface.
• no spanning-tree bpdufilter -- Enables BPDU filtering on the interface if the interface is in operational PortFast state and if you configure the spanning-treeportfastbpdufilterdefault command.

Use the spanning-treeportfastbpdufilterdefaultcommand to enable BPDU filtering on all ports that are already configured for PortFast.

Related Commands

To enable bridge protocol data unit (BPDU) guard on the interface, use the spanning-treebpduguard command in interface configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

Command Default

The setting that is already configured when you enter the spanning-treeportfastbpduguarddefault command .

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

BPDU guard prevents a port from receiving BPDUs. Typically, this feature is used in a service-provider environment where the network administrator wants to prevent an access port from participating in the spanning tree. If the port still receives a BPDU, it is put in the error-disabled state as a protective measure. This command has three states:

• spanning-tree bpduguard enable -- Unconditionally enables BPDU guard on the interface.
• spanning-tree bpduguard disable -- Unconditionally disables BPDU guard on the interface.
• no spanning-tree bpduguard --E nables BPDU guard on the interface if it is in the operational PortFast state and if the spanning-treeportfastbpduguarddefault command is configured.

Related Commands

To enable Bridge Assurance on all network ports on the switch, use the spanning-treebridgeassurancecommand in global configuration mode. To disable Bridge Assurance, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

Bridge Assurance is enabled.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

Bridge Assurance protects against a unidirectional link failure or other software failure and a device that continues to forward data traffic when it is no longer running the spanning tree algorithm.

Bridge Assurance is enabled only on spanning tree network ports that are point-to-point links. Both ends of the link must have Bridge Assurance enabled. If the device on one side of the link has Bridge Assurance enabled and the device on the other side either does not support Bridge Assurance or does not have this feature enabled, the connecting port is blocked.

Disabling Bridge Assurance causes all configured network ports to behave as normal spanning tree ports.

Related Commands

To set the path cost of the interface for Spanning Tree Protocol (STP) calculations, use the spanning-treecost command in interface configuration mode. To revert to the default value, use the no form of this command.

Syntax Description

Command Default

The default path cost is computed from the bandwidth setting of the interface; default path costs are:

Ethernet: 100 16-Mb Token Ring: 62 FDDI: 10 FastEthernet: 10 ATM 155: 6 GigibitEthernet: 1 HSSI: 647

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

When you specify a value for the cost argument, higher values indicate higher costs. This range applies regardless of the protocol type specified.

Related Commands

To display an error message when a loop due to a channel misconfiguration is detected, use the spanning-treeetherchannelguardmisconfig command in global configuration mode. To disable the error message, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

Error messages are displayed.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

EtherChannel uses either Port Aggregation Protocol (PAgP) or Link Aggregation Control Protocol (LACP) and does not work if the EtherChannel mode of the interface is enabled using the channel-group group-number mode on command.

The spanning-treeetherchannelguardmisconfig command detects two types of errors: misconfiguration and misconnection errors. A misconfiguration error is an error between the port-channel and an individual port. A misconnection error is an error between a switch that is channeling more ports and a switch that is not using enough Spanning Tree Protocol (STP) Bridge Protocol Data Units (BPDUs) to detect the error. In this case, the switch will only error disable an EtherChannel if the switch is a nonroot switch.

When an EtherChannel-guard misconfiguration is detected, this error message displays:

msgdef(CHNL_MISCFG, SPANTREE, LOG_CRIT, 0, "Detected loop due to etherchannel misconfiguration of %s %s")

To determine which local ports are involved in the misconfiguration, enter the showinterfacesstatuserr-disabled command. To check the EtherChannel configuration on the remote device, enter the showetherchannelsummarycommand on the remote device.

After you correct the configuration, enter the shutdown and the noshutdown commands on the associated port-channel interface.

Related Commands

To enable the extended-system ID feature on chassis that support 1024 MAC addresses, use the spanning-treeextendsystem-id command in global configuration mode. To disable the extended system identification, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

Enabled on systems that do not provide 1024 MAC addresses.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

The Cisco 7600 series router can support 64 or up to 1024 MAC addresses. For a Cisco 7600 series router with 64 MAC addresses, STP uses the extended-system ID and a MAC address to make the bridge ID unique for each VLAN.

You cannot disable the extended-system ID on a Cisco 7600 series router that supports 64 MAC addresses.

Enabling or disabling the extended-system ID updates the bridge IDs of all active Spanning Tree Protocol (STP) instances, which might change the spanning-tree topology.

Related Commands

To enable or disable the guard mode, use the spanning-treeguardcommand in interface configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

Command Default

Guard mode is disabled.

Command Modes

Interface configuration (config-if)

Command History

Related Commands

To configure a link type for a port, use the spanning-treelink-type command in the interface configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

Command Default

Link type is automatically derived from the duplex setting unless you explicitly configure the link type.

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

Rapid Spanning Tree Protocol Plus (RSTP+) fast transition works only on point-to-point links between two bridges.

By default, the switch derives the link type of a port from the duplex mode. A full-duplex port is considered as a point-to-point link while a half-duplex configuration is assumed to be on a shared link.

If you designate a port as a shared link, RSTP+ fast transition is forbidden, regardless of the duplex setting.

Related Commands

To enable loop guard as a default on all ports of a given bridge, use the spanning-treeloopguarddefault command in global configuration mode. To disable loop guard, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

Loop guard is disabled.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

Loop guard provides additional security in the bridge network. Loop guard prevents alternate or root ports from becoming the designated port due to a failure that could lead to a unidirectional link.

Loop guard operates only on ports that are considered point to point by the spanning tree.

The individual loop-guard port configuration overrides this command.

Related Commands

To switch between Per-VLAN Spanning Tree+ (PVST+), Rapid-PVST+, and Multiple Spanning Tree (MST) modes, use the spanning-treemode command in global configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

Command Default

pvst

Command Modes

Global configuration (config)

Command History

Usage Guidelines

Caution

Be careful when using the spanning-treemode command to switch between PVST+, Rapid-PVST+, and MST modes. When you enter the command, all spanning-tree instances are stopped for the previous mode and are restarted in the new mode. Using this command may cause disruption of user traffic.

Related Commands

To set the path cost and port-priority parameters for any Multiple Spanning Tree (MST) instance (including the Common and Internal Spanning Tree [CIST] with instance ID 0), use the spanning-treemst command in interface configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

Command Default

The defaults are as follows:

• cost depends on the port speed; the faster interface speeds indicate smaller costs. MST always uses long path costs.
• priority is 128.

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

Higher cost costvalues indicate higher costs. When entering the cost, do not include a comma in the entry; for example, enter 1000, not 1,000.

Higher port-priority priorityvalues indicate smaller priorities.

Related Commands

To enter MST-configuration submode, use the spanning-treemstconfiguration command in global configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

The default value for the Multiple Spanning Tree (MST) configuration is the default value for all its parameters:

• No VLANs are mapped to any MST instance (all VLANs are mapped to the Common and Internal Spanning Tree [CIST] instance).
• The region name is an empty string.
• The revision number is 0.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

The MST configuration consists of three main parameters:

• Instance VLAN mapping--See the instance command
• Region name--See the name(MSTconfigurationsubmode) command
• Configuration revision number--See the revision command

The abort and exit commands allow you to exit MST configuration submode. The difference between the two commands depends on whether you want to save your changes or not.

The exit command commits all the changes before leaving MST configuration submode. If you do not map secondary VLANs to the same instance as the associated primary VLAN, when you exit MST-configuration submode, a warning message displays and lists the secondary VLANs that are not mapped to the same instance as the associated primary VLAN. The warning message is as follows:

These secondary vlans are not mapped to the same instance as their primary:
-> 3

The abort command leaves MST-configuration submode without committing any changes.

Changing an MST-configuration submode parameter can cause connectivity loss. To reduce service disruptions, when you enter MST-configuration submode, make changes to a copy of the current MST configuration. When you are done editing the configuration, you can apply all the changes at once by using the exit keyword, or you can exit the submode without committing any change to the configuration by using the abort keyword.

In the unlikely event that two users commit a new configuration at exactly at the same time, this warning message displays:

% MST CFG:Configuration change lost because of concurrent access

Related Commands

To set the forward-delay timer for all the instances on the Cisco 7600 series router, use the spanning-treemstforward-timecommand in global configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

Command Default

seconds is 15

Command Modes

Global configuration (config)

Command History

Related Commands

To set the hello-time delay timer for all the instances on the Cisco 7600 series router, use the spanning-treemsthello-time command in global configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

Command Default

2 seconds

Command Modes

Global configuration (config)

Command History

Usage Guidelines

If you do not specify the hello-time value, the value is calculated from the network diameter.

Related Commands

To set the max-age timer for all the instances on the Cisco 7600 series router, use the spanning-treemstmax-age command in global configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

Command Default

20 seconds

Command Modes

Global configuration (config)

Command History

Related Commands

To specify the number of possible hops in the region before a bridge protocol data unit (BPDU) is discarded, use the spanning-treemstmax-hops command in global configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

Command Default

20 hops

Command Modes

Global configuration (config)

Command History

Related Commands

To configure a port to transmit only prestandard bridge protocol data units (BPDUs), use the spanning-treemstpre-standard command in interface configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

The default is to automatically detect prestandard neighbors.

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

Even with the default configuration, the port can receive both prestandard and standard BPDUs.

Prestandard BPDUs are based on the Cisco IOS Multiple Spanning Tree (MST) implementation that was created before the IEEE standard was finalized. Standard BPDUs are based on the finalized IEEE standard.

If you configure a port to transmit prestandard BPDUs only, the prestandard flag displays in the showspanning-treecommands. The variations of the prestandard flag are as follows:

• Pre-STD (or pre-standard in long format)--This flag displays if the port is configured to transmit prestandard BPDUs and if a prestandard neighbor bridge has been detected on this interface.
• Pre-STD-Cf (or pre-standard (config) in long format)--This flag displays if the port is configured to transmit prestandard BPDUs but a prestandard BPDU has not been received on the port, the autodetection mechanism has failed, or a misconfiguration, if there is no prestandard neighbor, has occurred.
• Pre-STD-Rx (or pre-standard (rcvd) in long format)--This flag displays when a prestandard BPDU has been received on the port but it has not been configured to send prestandard BPDUs. The port will send prestandard BPDUs, but we recommend that you change the port configuration so that the interaction with the prestandard neighbor does not rely only on the autodetection mechanism.

If the MST configuration is not compatible with the prestandard (if it includes an instance ID greater than 15), only standard MST BPDUs are transmitted, regardless of the STP configuration on the port.

Related Commands

To set the bridge priority for an instance, use the spanning-treemstprioritycommand in global configuration mode. To return to the default setting, use the no form of this command.

Syntax Description

Command Default

priority is 32768

Command Modes

Global configuration (config)

Command History

Usage Guidelines

You can set the bridge priority in increments of 4096 only. When you set the priority, valid values are 0, 4096, 8192, 12288, 16384, 20480, 24576, 28672, 32768, 36864, 40960, 45056, 49152, 53248, 57344, and 61440.

You can set the priority to 0 to make the switch root.

You can enter instanceas a single instance or a range of instances, for example, 0-3,5,7-9.

Related Commands

To designate the primary and secondary root switch and set the timer value for an instance, use the spanning-treemstrootcommand in global configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

Command Default

The spanning-tree mst root command has no default settings.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

You can enter instanceas a single instance or a range of instances, for example, 0-3,5,7-9.

The spanning-treemstrootsecondary value is 16384.

The diameterdiameter and hello-timesecondskeywords and arguments are available for instance 0 only.

If you do not specify the secondsargument, the value for it is calculated from the network diameter.

Related Commands

To override the global Per-VLAN Spanning Tree (PVST) simulation setting for a port, use the spanning-treemstsimulatepvst interface command in interface configuration mode. To return to the default PVST simulation setting, use the no form of this command.

Syntax Description

Command Default

PVST simulation is enabled.

Command Modes

Interface configuration (config-if)

Command History

Usage Guidelines

PVST simulation is enabled by default so that an interface can interoperate between Multiple Spanning Tree (MST) and Rapid Per-VLAN Spanning Tree Plus (PVST+). To prevent an accidental connection to a device that does not run MST as the default Spanning Tree Protocol (STP) mode, you can disable PVST simulation. If you disable PVST simulation, the MST-enabled port moves to the blocking state once it detects it is connected to a Rapid PVST+-enabled port. This port remains in the inconsistent state until the port stops receiving Bridge Protocol Data Units (BPDUs), and then the port resumes the normal STP transition process.

Related Commands

To enable Per-VLAN Spanning Tree (PVST) simulation globally, enter the spanning-treemstsimulatepvstglobalcommand in global configuration mode. To disable PVST simulation globally, enter the noform of this command.

Syntax Description

This command has no arguments or keywords.

Command Default

PVST simulation is enabled.

Command Modes

Global configuration (config)

Command History

Usage Guidelines

PVST simulation is enabled by default so that all interfaces on the device interoperate between Multiple Spanning Tree (MST) and Rapid Per-VLAN Spanning Tree Plus (PVST+). To prevent an accidental connection to a device that does not run MST as the default Spanning Tree Protocol (STP) mode, you can disable PVST simulation. If you disable PVST simulation, the MST-enabled port moves to the blocking state once it detects it is connected to a Rapid PVST+-enabled port. This port remains in the inconsistent state until the port stops receiving Bridge Protocol Data Units (BPDUs), and then the port resumes the normal STP transition process.

To override the global PVST simulation setting for a port, enter the spanning-treemstsimulatepvst interface command in the interface command mode.

Related Commands

To set the default path-cost calculation method, use the spanning-tree pathcost method command in global configuration mode. To return to the default settings, use the no form of this command.

Syntax Description

Command Default

short

Command Modes

Global configuration (config)

Command History

Usage Guidelines

This command applies to all the spanning-tree instances on the Cisco 7600 series router.

The long path-cost calculation method utilizes all 32 bits for path-cost calculation and yields values in the range of 1 through 200,000,000.

The short path-cost calculation method (16 bits) yields values in the range of 1 through 65535.

Related Commands

To enable PortFast mode where the interface is immediately put into the forwarding state upon linkup without waiting for the timer to expire, use the spanning-treeportfast command in interface configuration mode. To return to the default settings, use the no form of this command.

Syntax Description