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Cisco IOS Interface and Hardware Component Command Reference
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Introduction
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A through B
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cable bundle through clock mode
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clock rate through cut-through
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D through E
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F through H
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I through K
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l2 vfi manual through loopback (PA-MC-8TE1 + port adapter)
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loopback (T1 interface) through nrzi-encoding
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O through R
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scramble through service-module t1 lbo
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service-module t1 linecode through show controllers satellite
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show controllers serial through show hw-module slot proc cpu
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show hw-module slot tech-support through show interfaces vg-anylan
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show interfaces vlan mapping through show scp
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show service-module serial through standby port
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squelch through system jumbomtu
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t1 through tug-2 e1 unframed
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tunnel bandwidth through yellow
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Table Of Contents
switchport capture allowed vlan
switchport port-security aging
switchport port-security mac-address
switchport port-security maximum
switchport port-security violation
switchport private-vlan host-association
switchport private-vlan mapping
switchport vlan mapping enable
squelch
To extend the Ethernet twisted-pair 10BASE-T capability beyond the standard 100 meters on the Cisco 4000 platform, use the squelch command in interface configuration mode. To restore the default, use the no form of this command.
squelch {normal | reduced}
no squelch
Syntax Description
Defaults
Normal range
Command Modes
Interface configuration
Command History
Examples
The following example extends the twisted-pair 10BASE-T capability on the cable attached to Ethernet interface 2:
Router(config)# interface ethernet 2Router(config-if)# squelch reducedsrp buffer-size
To make adjustments to buffer settings on the receive side for different priority traffic, use the srp buffer-size command in interface configuration mode. To disable buffer size configurations, use the no form of this command.
srp buffer-size receive [low buffer | medium buffer | high buffer]
no srp buffer-size receive [low buffer | medium buffer | high buffer]
Syntax Description
Defaults
low = 8192 kilobytes, medium = 4096 kilobytes, high = 4096 kilobytes
Command Modes
Interface configuration
Command History
Examples
The following example sets the buffer size for the receive side at the high setting of 17 kilobytes:
Router(config-if)# srp buffer-size receive high 17Related Commands
mtu
Adjusts the maximum packet size MTU size.
Transfers packets from the internal receive buffer to Cisco IOS software.
srp deficit-round-robin
To transfer packets from the internal receive buffer to Cisco IOS software, use the srp deficit-round-robin command in interface configuration mode. To disable the packet transfer, use the no form of this command.
srp deficit-round-robin [input | output] [low | medium | high ] [quantum number | deficit number]
no srp deficit-round-robin
Syntax Description
Defaults
quantum: 9216
deficit: 16384Command Modes
Interface configuration
Command History
Examples
The following example shows how to configure packets for the medium-priority input queue:
Router(config)# srp deficit-round-robin input medium deficit 15000Related Commands
srp loopback
To loop the spatial reuse protocol (SRP) interface on an OC-12c DPTIP, use the srp loopback command in interface configuration mode. To remove the loopback, use the no form of this command.
srp loopback {internal | line} {a | b}
no srp loopback
Syntax Description
Defaults
No loops are configured.
Command Modes
Interface configuration
Command History
Usage Guidelines
Use this command for troubleshooting purposes.
Examples
The following example configures the loopback test on the A side of the SRP interface:
Router(config-if)# srp loopback line asrp priority-map
To set priority mapping for transmitting and receiving packets, use the srp priority-map command in interface configuration mode. To disable priority mapping use the no form of this command.
srp priority-map {receive {low priority | medium priority | high priority | {transmit {medium priority | high priority}}
no srp priority-map
Syntax Description
Defaults
receive low: 1
receive medium: 3
receive high: 5
transmit high: 7Command Modes
Interface configuration
Command History
Usage Guidelines
The spatial reuse protocol (SRP) interface provides commands to enforce quality of service (QoS) functionality on the transmit side and receive side of Cisco routers. SRP uses the IP type of service (ToS) field values to determine packet priority.
The SRP interface classifies traffic on the transmit side into high- and low-priority traffic. High-priority traffic is rate shaped and has higher priority than low-priority traffic. You have the option to configure high- or low-priority traffic and can rate limit the high-priority traffic.
The srp priority-map transmit command enables the user to specify IP packets with values equal to or greater than the ToS value to be considered as high-priority traffic.
On the receive side, when WRED is enabled, SRP hardware classifies packets into high-, medium-, and low-priority packets on the basis of the IP ToS value. After classification, it stores the packet into the internal receive buffer. The receive buffer is partitioned for each priority packet. Cisco routers can employ WRED on the basis of the IP ToS value. Routers also employ the Deficit Round Robin (DRR) algorithm to transfer packets from the internal receive buffer to Cisco IOS software.
The srp priority-map receive command enables the user to classify packets as high, medium, or low based on the IP ToS value.
Examples
The following example configures Cisco 7500 series routers to transmit packets with priority greater than 5 as high-priority packets:
Router(config-if)# srp priority-map transmit high 6Related Commands
srp random-detect
To configure weighted RED (WRED) parameters on packets received through an spatial reuse protocol (SRP) interface, use the srp random-detect command in interface configuration mode. To return the value to the default, use the no form of this command.
srp random-detect {compute-interval interval | enable | input [low | medium | high] |
[exponential-weight weight | precedence precedence]}no srp random-detect
Syntax Description
Defaults
compute-interval: 128
weight: 6
precedence: 7Command Modes
Interface configuration
Command History
Examples
The following example configures WRED parameters on packets received through an SRP interface with a weight factor of 5:
Router(config-if)# srp random-detect input high exponential-weight 5srp shutdown
To disable the spatial reuse protocol (SRP) interface, use the srp shutdown command in interface configuration mode. To restart a disabled interface, use the no form of this command.
srp shutdown [a | b]
no srp shutdown [a | b]
Syntax Description
a
(Optional) Specifies side A of the SRP interface.
b
(Optional) Specifies side B of the SRP interface.
Defaults
The SRP interface continues to be enabled until this command is issued.
Command Modes
Interface configuration
Command History
Usage Guidelines
The srp shutdown command disables all functions on the specified side.
Examples
The following example turns off side A of the SRP interface:
Router(config-if)# srp shutdown asrp tx-traffic-rate
To limit the amount of high-priority traffic that the spatial reuse protocol (SRP) interface can handle, use the srp tx-traffic-rate command in interface configuration mode. Use the no form of this command to disable transmitted traffic rate.
srp tx-traffic-rate number
no srp tx-traffic-rate number
Syntax Description
Defaults
number: 10
Command Modes
Interface configuration
Command History
Examples
The following example configures SRP traffic to transmit at 1000 kilobits per second:
Router(config-if)# srp tx-traffic-rate 1000stack-mib portname
To specify a name string for a port, use the stack-mib portname command in interface configuration mode.
stack-mib portname portname
Syntax Description
Defaults
This command has no default settings.
Command Modes
Interface configuration
Command History
Usage Guidelines
Using the stack-mib command to set a name string to a port corresponds to the portName MIB object in the portTable of CISCO-STACK-MIB. portName is the MIB object in the portTable of CISCO-STACK-MIB. You can set this object to be descriptive text describing the function of the interface.
Examples
This example shows how to set a name to a port:
Router(config-if)# stack-mib portname portallRouter(config-if)#storm-control
To enable broadcast, multicast, or unicast storm control on a port or to specify the action taken when a storm occurs on a port, use the storm-control command in interface configuration mode. To disable storm control for broadcast, multicast, or unicast traffic or to disable the specified storm-control action, use the no form of this command.
storm-control {{broadcast | multicast | unicast} level level [lower-level] | action shutdown}
no storm-control {{broadcast | multicast | unicast} level | action shutdown}
Syntax Description
Defaults
Broadcast, multicast, and unicast storm control is disabled.
The default action is to filter traffic.Command Modes
Interface configuration
Command History
Usage Guidelines
Use the storm-control command to enable or disable broadcast, multicast, or unicast storm control on a port. After a port is disabled during a storm, use the no form of the shutdown interface configuration command to enable the port.
The suppression levels are entered as a percentage of total bandwidth. A suppression value of 100 percent means that no limit is placed on the specified traffic type. This command 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 that is causing the storm.
When a storm occurs and the action is to filter traffic, if the falling suppression level is not specified, the networking device blocks all traffic until the traffic rate drops below the rising suppression level. If the falling suppression level is specified, the networking device blocks traffic until the traffic rate drops below this level.
When a multicast or unicast storm occurs and the action is to filter traffic, the networking device blocks all traffic (broadcast, multicast, and unicast traffic) and sends only Spanning Tree Protocol (STP) packets.
When a broadcast storm occurs and the action is to filter traffic, the networking device blocks only broadcast traffic.
Examples
The following example shows how to enable broadcast storm control on a port with a 75.67 percent rising suppression level:
Router(config-if)# storm-control broadcast level 75.67The following example shows how to enable multicast storm control on a port with an 87 percent rising suppression level and a 65 percent falling suppression level:
Router(config-if)# storm-control multicast level 87 65The following example shows how to enable the shutdown action on a port:
Router(config-if)# storm-control action shutdownThe following example shows how to disable the shutdown action on a port:
Router(config-if)# no storm-control action shutdownRelated Commands
show storm-control
Displays the packet-storm control information.
shutdown (interface)
Disables an interface.
storm-control level
To set the suppression level, use the storm-control level command in interface configuration mode. To turn off the suppression mode, use the no form of this command.
storm-control {broadcast | multicast | unicast} level level[.level]
no storm-control {broadcast | multicast | unicast} level
Syntax Description
Command Default
All packets are passed.
Command Modes
Interface configuration (config-if)
Command History
Usage Guidelines
You can enter this command on switch ports and router ports.
Enter the storm-control level command to enable traffic storm control on the interface, configure the traffic storm-control level, and apply the traffic storm-control level to all traffic storm-control modes that are enabled on the interface.
Only one suppression level is shared by all three suppression modes. For example, if you set the broadcast level to 30 and set the multicast level to 40, both levels are enabled and set to 40.
The Cisco 7600 series router supports storm control for multicast and unicast traffic only on Gigabit Ethernet LAN ports. The switch supports storm control for broadcast traffic on all LAN ports.
The multicast and unicast keywords are supported on Gigabit Ethernet LAN ports only. These keywords are not supported on 10 Mbps, 10/100 Mbps, 100 Mbps, or 10-Gigabit Ethernet modules.
The period is required when you enter the fractional-suppression level.
The suppression level is entered as a percentage of the total bandwidth. A threshold value of 100 percent means that no limit is placed on traffic. A threshold value of 0 or 0.0 (fractional) percent means that all specified traffic is blocked on a port, with the following guidelines:
•
A fractional level value of 0.33 or lower is the same as 0.0 on the following modules:
–
–
–
–
•
•
Enter the show interfaces counters broadcast command to display the discard count.
Enter the show running-config command to display the enabled suppression mode and level setting.
To turn off suppression for the specified traffic type, you can do one of the following:
•
•
Examples
This example shows how to enable and set the suppression level:
Router(config-if)# storm-control broadcast level 30This example shows how to disable the suppression mode:
Router(config-if)# no storm-control multicast levelRelated Commands
show interfaces counters
Displays the traffic that the physical interface sees.
show running-config
Displays the status and configuration of the module or Layer 2 VLAN.
subslot
To add an IPSec VPN SPA to a Blade Failure Group, use the subslot command in redundancy-linecard configuration mode.
subslot slot subslot
Syntax Description
Defaults
No default behavior or values.
Command Modes
Redundancy-linecard configuration
Command History
12.2(18)SXE2
This command was introduced.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
Usage Guidelines
To complete the configuration of a Blade Failure Group, you must repeat the subslot command for each IPSec VPN SPA in the group.
Examples
The following example configures a Blade Failure Group that has a group ID of 1 and consists of two IPSec VPN SPAs—one IPSec VPN SPA is in slot 5, subslot 1 and one IPSec VPN SPA is in slot 6, subslot 1:
Router(config)# redundancyRouter(config-red)# linecard-group 1 feature-cardRouter(config-r-lc)# subslot 5/1Router(config-r-lc)# subslot 6/1Related Commands
switchport
Cisco 3550, 4000, and 4500 Series Switches
To put an interface that is in Layer 3 mode into Layer 2 mode for Layer 2 configuration, use the switchport command in interface configuration mode. To put an interface into Layer 3 mode, use the no form of this command.
switchport
no switchport
Cisco Catalyst 6500/6000 Series Switches and Cisco 7600 Series Routers
To modify the switching characteristics of the Layer 2-switched interface, use the switchport command (without keywords). Use the no form of this command (without keywords) to return the interface to the routed-interface status and cause all further Layer 2 configuration to be erased. Use the switchport commands (with keywords) to configure the switching characteristics.
switchport
switchport {host | nonegotiate}
no switchport
no switchport nonegotiate
Syntax Description
Cisco 3550, 4000, and 4500 Series Switches
This command has no arguments or keywords.
Cisco Catalyst 6500/6000 Series Switches and Cisco 7600 Series Routers
host
Optimizes the port configuration for a host connection.
nonegotiate
Specifies that the device will not engage in negotiation protocol on this interface.
Defaults
Cisco 3550, 4000, and 4500 Series Switches
All interfaces are in Layer 2 mode.
Catalyst 6500/6000 Series Switches and 7600 Series Routers
The default access VLAN and trunk-interface native VLAN are default VLANs that correspond to the platform or interface hardware.
Command Modes
Interface configuration
Command History
Usage Guidelines
Cisco 3550, 4000, and 4500 Series Switches
Use the no switchport command to put the interface into the routed-interface status and to erase all Layer 2 configurations. You must use this command before assigning an IP address to a routed port. Entering the no switchport command shuts down the port and then reenables it, which might generate messages on the device to which the port is connected.
You can verify the switchport status of an interface by entering the show running-config privileged EXEC command.
Cisco Catalyst 6500/6000 Series Switches and Cisco 7600 Series Routers
You must enter the switchport command without any keywords to configure the LAN interface as a Layer 2 interface before you can enter additional switchport commands with keywords. This action is required only if you have not entered the switchport command for the interface.
Entering the no switchport command shuts down the port and then reenables it. This action may generate messages on the device to which the port is connected.
To optimize the port configuration, entering the switchport host command sets the switch port mode to access, enables spanning tree PortFast, and disables channel grouping. Only an end station can accept this configuration.
Because spanning-tree PortFast is enabled, you should enter the switchport host command only on ports that are connected to a single host. Connecting other Cisco 7600 series routers, hubs, concentrators, switches, and 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.
The no form of the switchport nonegotiate command removes nonegotiate status.
When using the nonegotiate keyword, Dynamic Inter-Switch Link Protocol and Dynamic Trunking Protocol (DISL/DTP)-negotiation packets are not sent on the interface. The device trunks or does not trunk according to the mode parameter given: access or trunk. This command returns an error if you attempt to execute it in dynamic (auto or desirable) mode.
You must force a port to trunk before you can configure it as a SPAN-destination port. Use the switchport nonegotiate command to force the port to trunk.
Examples
Cisco 3550, 4000, and 4500 Series Switches
The following example shows how to cause an interface to cease operating as a Layer 2 port and become a Cisco-routed (Layer 3) port:
Router(config-if)# no switchportCisco Catalyst 6500/6000 Series Switches and Cisco 7600 Series Routers
The following example shows how to cause the port interface to stop operating as a Cisco-routed port and convert to a Layer 2-switched interface:
Router(config-if)# switchportRouter(config-if)#
Note
The following example shows how to optimize the port configuration for a host connection:
Router(config-if)# switchport hostswitchport mode will be set to accessspanning-tree portfast will be enabledchannel group will be disabledRouter(config-if)#This example shows how to cause a port interface that has already been configured as a switched interface to refrain from negotiating trunking mode and act as a trunk or access port (depending on the mode set):
Router(config-if)# switchport nonegotiateRouter(config-if)#The following example shows how to cause an interface to cease operating as a Cisco-routed port and to convert it into a Layer 2 switched interface:
Router(config-if)# switchport
Note
ports. All physical ports on such platforms are assumed to be Layer 2 switched interfaces.Related Commands
switchport access vlan
To set the VLAN when the interface is in access mode, use the switchport access vlan command in interface configuration mode. To reset the access-mode VLAN to the appropriate default VLAN for the device, use the no form of this command.
switchport access vlan vlan-id
no switchport access vlan
Syntax Description
Defaults
The defaults are as follows:
•
•
Command Modes
Interface configuration
Command History
Usage Guidelines
You must enter the switchport command without any keywords to configure the LAN interface as a Layer 2 interface before you can enter the switchport access vlan command. This action is required only if you have not entered the switchport command for the interface.
Entering the no switchport command shuts down the port and then reenables it. This action may generate messages on the device to which the port is connected.
The no form of the switchport access vlan command resets the access-mode VLAN to the appropriate default VLAN for the device.
Examples
This example shows how to cause the port interface to stop operating as a Cisco-routed port and convert to a Layer 2 switched interface:
Router(config-if)# switchport
Note
This example shows how to cause a port interface that has already been configured as a switched interface to operate in VLAN 2 instead of the platform's default VLAN in the interface-configuration mode:
Router(config-if)# switchport access vlan 2Related Commands
show interfaces switchport
Displays the administrative and operational status of a switching (nonrouting) port.
switchport
Configures a LAN interface as a Layer 2 interface.
switchport autostate exclude
To exclude a port from the VLAN interface link-up calculation, use the switchport autostate exclude command in interface configuration mode. To return to the default settings, use the no form of this command.
switchport autostate exclude
no switchport autostate exclude
Syntax Description
This command has no keywords or arguments.
Defaults
All ports are included in the VLAN interface link-up calculation.
Command Modes
Interface configuration
Command History
Usage Guidelines
You must enter the switchport command without any keywords to configure the LAN interface as a Layer 2 interface before you can enter the switchport autostate exclude command. This action is required only if you have not entered the switchport command for the interface.
Note
A VLAN interface configured on the MSFC is considered up if there are ports forwarding in the associated VLAN. When all ports on a VLAN are down or blocking, the VLAN interface on the MSFC is considered down. For the VLAN interface to be considered up, all the ports in the VLAN need to be up and forwarding. You can enter the switchport autostate exclude command to exclude a port from the VLAN interface link-up calculation.
The switchport autostate exclude command marks the port to be excluded from the interface VLAN up calculation when there are multiple ports in the VLAN.
The show interface interface switchport command displays the autostate mode if the mode has been set. If the mode has not been set, the autostate mode is not displayed.
Examples
This example shows how to exclude a port from the VLAN interface link-up calculation:
Router(config-if)# switchport autostate excludeThis example shows how to include a port in the VLAN interface link-up calculation:
Router(config-if)# no switchport autostate excludeRelated Commands
show interfaces switchport
Displays the administrative and operational status of a switching (nonrouting) port.
switchport
Configures a LAN interface as a Layer 2 interface.
switchport backup
To configure an interface as a Flexlink backup interface, use the switchport backup command in interface configuration mode. To disable Flexlink, use the no form of this command.
switchport backup interface type number
no switchport backup interface type number
Syntax Description
interface type number
Specifies the interface type and the module and port number to configure as a Flexlink backup interface.
Defaults
Disabled
Command Modes
Interface configuration
Command History
12.2(18)SXF
Support for this command was introduced on the Supervisor Engine 720.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
Usage Guidelines
When you enable Flexlink, both the active and the standby links are up physically and mutual backup is provided.
Flexlink is supported on Layer 2 interfaces only and does not support routed ports.
Flexlink does not switch back to the original active interface after recovery.
The number designates the module and port number. Valid values depend on the chassis and module that are used. For example, if you have a 48-port 10/100BASE-T Ethernet module that is installed in a 13-slot chassis, valid values for the slot number are from 1 to 13 and valid values for the port number are from 1 to 48.
Flexlink is designed for simple access topologies (two uplinks from a leaf node). You must ensure that there are no loops from the wiring closet to the distribution/core network to enable Flexlink to perform correctly.
Flexlink converges faster for directly connected link failures only. Any other network failure has no improvement with Flexlink fast convergence.
You must enter the switchport command without any keywords to configure the LAN interface as a Layer 2 interface before you can enter the switchport autostate exclude command. This action is required only if you have not entered the switchport command for the interface.
Note
Examples
This example shows how to enable Flexlink on an interface:
Router(config-if)# switchport backup interface fastethernet 4/1This example shows how to disable Flexlink on an interface:
Router(config-if)# switchport backup interface fastethernet 4/1Related Commands
switchport block unicast
To prevent the unknown unicast packets from being forwarded, use the switchport block unicast command in interface configuration mode. To allow the unknown unicast packets to be forwarded, use the no form of this command.
switchport block unicast
no switchport block unicast
Syntax Description
This command has no arguments or keywords.
Defaults
The default settings are as follows:
•
•
Command Modes
Interface configuration
Command History
12.2(18)SXE
Support for this command was introduced on the Supervisor Engine 720.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
Usage Guidelines
You can block the unknown unicast traffic on the switch ports.
Blocking the unknown unicast traffic is not automatically enabled on the switch ports; you must explicitly configure it.
Note
You can verify your setting by entering the show interfaces interface-id switchport command.
Examples
This example shows how to block the unknown unicast traffic on an interface:
Router(config-if)# switchport block unicastRelated Commands
show interfaces switchport
Displays the administrative and operational status of a switching (nonrouting) port.
switchport capture
To configure the port to capture VACL-filtered traffic, use the switchport capture command in interface configuration mode. To disable the capture mode on the port, use the no form of this command.
switchport capture
no switchport capture
Syntax Description
This command has no keywords or arguments.
Defaults
Disabled
Command Modes
Interface configuration
Command History
Usage Guidelines
You must enter the switchport command without any keywords to configure the LAN interface as a Layer 2 switched interface before you can enter additional switchport commands with keywords. This action is required only if you have not entered the switchport command for the interface.
The VACL capture function for the NAM is supported on the Supervisor Engine 720 but is not supported with the IDSM-2.
The switchport capture command applies only to Layer 2 switched interfaces.
WAN interfaces support only the capture functionality of VACLs.
Entering the no switchport command shuts down the port and then reenables it. This action may generate messages on the device to which the port is connected.
Entering the switchport capture command sets the capture function on the interface so that the packets with the capture bit set are received by the interface.
There is no restriction on the order that you enter the switchport capture and switchport capture allowed vlan commands. The port does not become a capture port until you enter the switchport capture (with no arguments) command.
The capture port must allow the destination VLANs of the captured packets. Once you enable a capture port, the packets are allowed from all VLANs by default, the capture port is on longer in the originally configured mode, and the capture mode enters monitor mode. In monitor mode, the capture port does the following:
•
•
•
•
•
Examples
This example shows how to configure an interface to capture VACL-filtered traffic:
Router(config-if)# switchport captureRelated Commands
switchport capture allowed vlan
To specify the destination VLANs of the VACL-filtered traffic, use the switchport capture allowed vlan command in interface configuration mode. To clear the configured-destination VLAN list and return to the default settings, use the no form of this command.
switchport capture allowed vlan {add | all | except | remove} vlan-id [,vlan-id[,vlan-id[,...]]]
no switchport capture allowed vlan
Syntax Description
Defaults
all
Command Modes
Interface configuration
Command History
Usage Guidelines
You must enter the switchport command without any keywords to configure the LAN interface as a Layer 2-switched interface before you can enter additional switchport commands with keywords. This action is required only if you have not entered the switchport command for the interface.
The switchport capture allowed vlan command applies only to Layer 2-switched interfaces.
Entering the no switchport command shuts down the port and then reenables it. This action may generate messages on the device to which the port is connected.
You can enter the vlan-id as a single VLAN, a group of VLANs, or both. For example, you would enter switchport capture allowed vlan 1-1000, 2000, 3000-3100.
There is no restriction on the order in which you enter the switchport capture and switchport capture allowed vlan commands. The port does not become a capture port until you enter the switchport capture (with no arguments) command.
WAN interfaces support only the capture functionality of VACLs.
Examples
This example shows how to add the specified VLAN to capture VACL-filtered traffic:
Router(config-if)# switchport capture allowed vlan add 100Related Commands
switchport dot1q ethertype
To specify the EtherType value to be programmed on the interface, use the switchport dot1q ethertype command in interface configuration mode. To return to the default settings, use the no form of this command.
switchport dot1q ethertype value
no switchport dot1q ethertype value
Syntax Description
Defaults
The value is 0x8100.
Command Modes
Interface configuration
Command History
Usage Guidelines
You can configure a custom EtherType-field value on trunk ports and on access ports.
Each port supports only one EtherType-field value. A port that is configured with a custom EtherType-field value does not recognize frames that have any other EtherType-field value as tagged frames.
Caution
You can configure a custom EtherType-field value on the following modules:
•
•
•
Note
9 through 16).•
•
•
•
•
You cannot configure a custom EtherType-field value on the ports in an EtherChannel.
You cannot form an EtherChannel from ports that are configured with custom EtherType-field values.
Examples
This example shows how to set the EtherType value to be programmed on the interface:
Router (config-if)# switchport dot1q ethertype 1234Related Commands
show interfaces switchport
Displays the administrative and operational status of a switching (nonrouting) port.
switchport mode
To set the interface type, use the switchport mode command in interface configuration mode. Use the appropriate no form of this command to reset the mode to the appropriate default mode for the device.
Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
switchport mode {access | trunk}
no switchport mode
Cisco Catalyst 6500/6000 Series Switches
switchport mode {access | dot1q-tunnel | dynamic {auto | desirable} | trunk}
no switchport mode
Cisco 7600 Series Routers
switchport mode {access | dot1q-tunnel | dynamic {auto | desirable} | private-vlan | trunk}
no switchport mode
switchport mode private-vlan {host | promiscuous}
no switchport mode private-vlan
Syntax Description
Defaults
Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
The default is access mode.
Cisco Catalyst 6500/6000 Switches
The default mode is dependent on the platform; it should be either dynamic auto for platforms that are intended as wiring closets or dynamic desirable for platforms that are intended as backbone switches. The default for PVLAN ports is that no mode is set.
Cisco 7600 Series Routers
The defaults are as follows:
•
•
Command Modes
Interface configuration
Command History
Usage Guidelines
Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
If you enter a forced mode, the interface does not negotiate the link to the neighboring interface. Ensure that the interface ends match.
The no form of the command is not supported on the Cisco 2600 series, Cisco 3600 series, and Cisco 3700 series routers.
Cisco Catalyst 6500/6000 Switches and Cisco 7600 Series Routers
If you enter access mode, the interface goes into permanent nontrunking mode and negotiates to convert the link into a nontrunk link even if the neighboring interface does not agree to the change.
If you enter trunk mode, the interface goes into permanent trunking mode and negotiates to convert the link into a trunk link even if the neighboring interface does not agree to the change.
If 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.
If you enter dynamic desirable mode, the interface becomes a trunk interface if the neighboring interface is set to trunk, desirable, or auto mode.
If you configure a port as a promiscuous or host-PVLAN port and one of the following applies, the port becomes inactive:
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If you delete a private-port PVLAN association or mapping, or if you configure a private port as a SPAN destination, the deleted private-port PVLAN association or mapping or the private port that is configured as a SPAN destination becomes inactive.
If you enter dot1q-tunnel mode, PortFast Bridge Protocol Data Unit (BPDU) filtering is enabled and Cisco Discovery Protocol (CDP) is disabled on protocol-tunneled interfaces.
Examples
Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
The following example shows how to set the interface to access desirable mode:
Router(config-if)# switchport mode access
The following example shows how to set the interface to trunk mode:
Router(config-if)# switchport mode trunk
Cisco Catalyst 6500/6000 Switches and Cisco 7600 Series Routers
The following example shows how to set the interface to dynamic desirable mode:
Router(config-if)# switchport mode dynamic desirableRouter(config-if)#The following example shows how to set a port to PVLAN-host mode:
Router(config-if)# switchport mode private-vlan hostRouter(config-if)#The following example shows how to set a port to PVLAN-promiscuous mode:
Router(config-if)# switchport mode private-vlan promiscuousRouter(config-if)#Related Commands
switchport port-security
To enable port security on an interface, use the switchport port-security command in interface configuration mode. To disable port security, use the no form of this command.
switchport port-security
no switchport port-security
Syntax Description
This command has no keywords or arguments.
Defaults
Disabled
Command Modes
Interface configuration
Command History
Usage Guidelines
Follow these guidelines when configuring port security:
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Examples
This example shows how to enable port security:
Router(config-if)# switchport port-securityThis example shows how to disable port security:
Related Commands
switchport port-security aging
To configure the port security aging, use the switchport port-security aging time command in interface configuration mode. To disable aging, use the no form of this command.
switchport port-security aging {time time | type {absolute | inactivity}}
no switchport port-security aging
Syntax Description
Defaults
The defaults are as follows:
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Command Modes
Interface configuration
Command History
Usage Guidelines
Follow these guidelines when configuring port security:
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You can apply one of two types of aging for automatically learned addresses on a secure port:
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Examples
This example shows how to set the aging time as 2 hours:
Router(config-if)# switchport port-security aging time 120This example shows how to set the aging time as 2 minutes:
Router(config-if)# switchport port-security aging time 2This example shows how to set the aging type on a port to absolute aging:
Router(config-if) switchport port-security aging type absoluteThis example shows how to set the aging type on a port to inactivity aging:
Router(config-if) switchport port-security aging type inactivityRelated Commands
switchport port-security mac-address
To add a MAC address to the list of secure MAC addresses, use the switchport port-security mac-address command. To remove a MAC address from the list of secure MAC addresses, use the no form of this command.
switchport port-security mac-address {mac-addr | {sticky [mac-addr]} [vlan access | voice]}
no switchport port-security mac-address {mac-addr | {sticky [mac-addr]} [vlan access | voice]}
Syntax Description
Defaults
This command has no default settings.
Command Modes
Interface configuration
Command History
Usage Guidelines
If you configure fewer secure MAC addresses than the maximum number of secure MAC addresses on all interfaces, the remaining MAC addresses are dynamically learned.
To clear multiple MAC addresses, you must enter the no form of this command once for each MAC address to be cleared.
The vlan-list argument is visible only if the port has been configured and is operational as a trunk. Enter the switchport mode trunk command and then enter the switchport nonegotiate command.
The sticky keyword configures the dynamic MAC addresses as sticky on an interface. Sticky MAC addresses configure the static Layer 2 entry to stay sticky to a particular interface. This feature can prevent MAC moves or prevent the entry from being learned on a different interface.
You can configure the sticky feature even when the port security feature is not enabled on the interface. It becomes operational once port security is enabled on the interface.
Note
You can configure MAC address with voice keyword only when there is a valid voice vlan configured for that port.
When port security is enabled, disabling the sticky feature causes all configured and learned sticky addresses to be deleted from the configuration and converted into dynamic secure addresses.
When port security is disabled, disabling the sticky feature causes all configured and learned sticky addresses to be deleted from the configuration.
Examples
This example shows how to configure a secure MAC address:
Router(config-if)# switchport port-security mac-address 1000.2000.3000This example shows how to delete a secure MAC address from the address table:
Router(config-if)# no switchport port-security mac-address 1000.2000.3000This example shows how to enable the sticky feature on an interface:
Router(config-if)# switchport port-security mac-address stickyThis example shows how to disable the sticky feature on an interface:
Router(config-if)# no switchport port-security mac-address stickyThis example shows how to make a specific MAC address as a sticky address:
Router(config-if)# switchport port-security mac-address sticky 0000.0000.0001This example shows how to delete a specific sticky address:
Router(config-if)# no switchport port-security mac-address sticky 0000.0000.0001This example shows how to delete all sticky and static addresses that are configured on an interface:
Router(config-if)# no switchport port-security mac-addressRelated Commands
switchport port-security maximum
To set the maximum number of secure MAC addresses on a port, use the switchport port-security maximum command in interface configuration mode. To return to the default settings, use the no form of this command.
switchport port-security maximum maximum [vlan vlan | vlan-list]
no switchport port-security maximum
Syntax Description
Defaults
This command has no default setings.
Command Modes
Interface configuration
Command History
Usage Guidelines
If you enter this command more than once, subsequent use of this command overrides the previous value of maximum. If the new maximum argument is larger than the current number of the secured addresses on this port, there is no effect except to increase the value of the maximum.
If the new maximum is smaller than the old maximum and there are more secure addresses on the old maximum, the command is rejected.
If you configure fewer secure MAC addresses than the maximum number of secure MAC addresses on the port, the remaining MAC addresses are dynamically learned.
Once the maximum number of secure MAC addresses for the port is reached, no more addresses are learned on that port even if the per-VLAN port maximum is different from the aggregate maximum number.
You can override the maximum number of secure MAC addresses for the port for a specific VLAN or VLANs by entering the switchport port-security maximum maximum vlan vlan | vlan-list command.
The vlan-list argument allows you to enter ranges, commas, and delimited entries such as 1,7,9-15,17.
The vlan-list argument is visible only if the port has been configured and is operational as a trunk. Enter the switchport mode trunk command and then enter the switchport nonegotiate command.
Examples
This example shows how to set the maximum number of secure MAC addresses that are allowed on this port:
Router(config-if)# switchport port-security maximum 5This command shows how to override the maximum set for a specific VLAN:
Router(config-if)# switchport port-security maximum 3 vlan 102Related Commands
show port-security
Display information about the port-security setting.
switchport nonegotiate
Configures the LAN port into permanent trunking mode.
switchport port-security violation
To set the action to be taken when a security violation is detected, use the switchport port-security violation command in interface configuration mode. To return to the default settings, use the no form of this command.
switchport port-security violation{shutdown | restrict | protect}
no switchport port-security violation{shutdown | restrict | protect}
Syntax Description
Command Default
The port security violation is shutdown.
Command Modes
Interface configuration (config-if)
Command History
Usage Guidelines
When a security violation is detected, one of the following actions occurs:
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Platform port-security disable traps is configurable only when the violation mode is set to protect. When this option is configured, drop entries will not be installed into hardware for violating addresses, thus allowing traffic to continue to flow to violating address from legitimate ports. To protect switch CPU against overload when this option is enabled, we recommend that you configure the port-security rate-limiter to 2000 packets per second with a burst rate of 10.
Note
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Examples
This example shows how to set the action to be taken when a security violation is detected:
Router(config-if)# switchport port-security violation restrictThis example allows the traffic to a secured MAC address on one port to flow even in the presence of violations on other ports while in protect mode.
Router(config-if)# switchport port-security violation protectRouter(config-if)# platform port-security disable trapsRelated Commands
switchport private-vlan host-association
To define a PVLAN association for an isolated or community port, use the switchport private-vlan host-association command in interface configuration mode. To remove the PVLAN mapping from the port, use the no form of this command.
switchport private-vlan host-association primary-vlan-id secondary-vlan-id
no switchport private-vlan host-association
Syntax Description
Defaults
No PVLAN is configured.
Command Modes
Interface configuration
Command History
Usage Guidelines
There is no run-time effect on the port unless it is in PVLAN-host mode. If the port is in PVLAN-host mode but neither of the VLANs exist, the command is allowed but the port is made inactive.
The secondary VLAN may be an isolated or community VLAN.
Examples
This example shows how to configure a port with a primary VLAN (VLAN 18) and secondary VLAN (VLAN 20):
Router(config-if)# switchport private-vlan host-association 18 20This example shows how to remove the PVLAN association from the port:
Router(config-if)# no switchport private-vlan host-associationRelated Commands
switchport private-vlan mapping
To define the PVLAN mapping for a promiscuous port, use the switchport private-vlan mapping command in interface configuration mode. To clear all mappings from the primary VLAN, use the no form of this command.
switchport private-vlan mapping primary-vlan-id secondary-vlan-list | add secondary-vlan-list | remove secondary-vlan-list
no switchport private-vlan mapping
Syntax Description
Defaults
No PVLAN mappings are configured.
Command Modes
Interface configuration
Command History
Usage Guidelines
There is no run-time effect on the port unless it is in PVLAN-promiscuous mode. If the port is in PVLAN-promiscuous mode but the VLANs do not exist, the command is allowed but the port is made inactive.
The secondary VLAN may be an isolated or community VLAN.
Examples
This example shows how to configure the mapping of primary VLAN 18 to secondary isolated VLAN 20 on a port:
Router(config-if)# switchport private-vlan mapping 18 20This example shows how to add a VLAN to the mapping:
Router(config-if)# switchport private-vlan mapping 18 add 21This example shows how to remove the PVLAN mapping from the port:
Router(config-if)# no switchport private-vlan mappingRelated Commands
show interfaces private-vlan mapping
Displays the information about the PVLAN mapping for VLAN SVIs.
switchport trunk
To set the trunk characteristics when the interface is in trunking mode, use the switchport trunk command in interface configuration mode. To reset all of the trunking characteristics back to the original defaults, use the no form of this command.
Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
switchport trunk {encapsulation dot1q | native vlan | allowed vlan}
no switchport trunk {encapsulation dot1q | native vlan | allowed vlan}
Cisco 7600 Series Routers and Catalyst 6500 Series Switches
switchport trunk {encapsulation {isl | dot1q [ethertype value] | negotiate}} | { native vlan {tag | vlan-id}} | {allowed vlan vlan-list} | {pruning vlan vlan-list}
no switchport trunk {encapsulation {isl | dot1q [ethertype value] | negotiate} | native vlan [tag]| allowed vlan | pruning vlan}
Syntax Description
Defaults
Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
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Cisco 7600 Series Routers and Catalyst 6500 Series Switches
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Command Modes
Interface configuration (config-if)
Command History
Usage Guidelines
802.1Q Trunks
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Cisco 2600 Series, Cisco 3600 Series, and Cisco 3700 Series Routers
The switchport trunk encapsulation command is supported only for platforms and interface hardware that can support 802.1Q formats.
The vlan-list format is all | none | add | remove | except vlan-list[,vlan-list...] where:
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Cisco 7600 Series Routers and Catalyst 6500 Series Switches
This command is not supported on GE Layer 2 WAN ports.
The switchport trunk encapsulation dot1q command is supported only for platforms and interface hardware that can support both ISL and 802.1Q formats. Only 802.1Q encapsulation is supported by shared port adapters (SPAs).
If you enter the switchport trunk encapsulation isl command on a port channel containing an interface that does not support ISL-trunk encapsulation, the command is rejected.
You can enter the switchport trunk allowed vlan command on interfaces where the span destination port is either a trunk or an access port.
You can enter the switchport trunk native vlan tag command to enable the tagging of native VLAN traffic on a per-port basis. When tagging is enabled, all the packets on the native VLAN are tagged and all incoming untagged data packets are dropped, but untagged control packets are accepted. When tagging is disabled, the native VLAN packets going out on trunk ports are not tagged and the incoming untagged packets are allowed and assigned to the native VLAN. The no switchport trunk native vlan tag command overrides the vlan dot1q tag native command for global tagging.
Note
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The dot1q ethertype value keyword and argument are not supported on port-channel interfaces. You can enter the command on the individual port interface only. Also, you can configure the ports in a channel group to have different EtherType configurations.
Caution
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The vlan-list format is all | none | add | remove | except [vlan-list[,vlan-list...]] where:
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To specify a range of VLANs, enter the smaller VLAN number first, separated by a hyphen and the larger VLAN number at the end of the range.
Do not enable the reserved VLAN range (1006 to 1024) on trunks when connecting a Cisco 7600 series router running the Cisco IOS software on both the supervisor engine and the Multilayer Switch Feature Card (MSFC) to a Cisco 7600 series router running the Catalyst operating system. These VLANs are reserved in Cisco 7600 series routers running the Catalyst operating system. If enabled, Cisco 7600 series routers running the Catalyst operating system may disable the ports if a trunking channel is between these systems.
Examples
The following example shows how to cause a port interface configured as a switched interface to encapsulate in 802.1Q trunking format regardless of its default trunking format in trunking mode:
Router(config-if)# switchport trunk encapsulation dot1q
The following example shows how to configure the Layer 2 port to tag native VLAN traffic:
Router(config-if)# switchport trunk native vlan tagRelated Commands
show interfaces switchport
Displays administrative and operational status of a switching (nonrouting) port.
vlan dot1q tag native
Enables dot1q tagging for all VLANs in a trunk.
switchport vlan mapping
To map the traffic arriving on the VLAN original-vlan-id to the VLAN translated-vlan-id and the traffic that is internally tagged with the VLAN translated-vlan-id with the VLAN original-vlan-id before leaving the port, use the switchport vlan mapping command in interface configuration mode. To clear the mapping between a pair of VLANs or clear all the mappings that are configured on the switch port, use the no form of this command.
switchport vlan mapping original-vlan-id translated-vlan-id
no switchport vlan mapping {original-vlan-id translated-vlan-id | all}
Syntax Description
Defaults
No mappings are configured on any switch port.
Command Modes
Interface configuration
Command History
Usage Guidelines
This command is not supported on Cisco 7600 series routers that are configured with a Supervisor Engine 2.
This command is not supported on GE Layer 2 WAN ports.
You must enable VLAN translation on the port where you want VLAN translation to work. Use the switchport vlan mapping enable command to enable VLAN translation.
Do not remove the VLAN that you are translating from the trunk. When you map VLANs, make sure that both VLANs are allowed on the trunk that carries the traffic.
Table 170 lists the VLAN translation, the type of VLAN translation support, the number of ports that you can configure per port group, and the trunk type for each module that supports VLAN translation.
The mapping that you configured using the switchport vlan mapping command does not become effective until the switch port becomes an operational trunk port.
The VLAN mapping that is configured on a port may apply to all the other ports on the same ASIC. In some cases, a mapping that is configured on one of the ports on an ASIC can overwrite a mapping that is already configured on another port on the same ASIC.
The port VLAN mapping is applied to all the ports on a port ASIC if that ASIC does not support per-port VLAN mapping.
If you configure VLAN mapping on the port ASIC that is a router port, the port-VLAN mapping does not take effect until the port becomes a switch port.
You can map any two VLANs regardless of the trunk types carrying the VLANs.
Examples
This example shows how to map the original VLAN to the translated VLAN:
Router(config-if)# switchport vlan mapping 100 201This example shows how to clear the mappings that are between a pair of VLANs:
Router(config-if)# no switchport vlan mapping 100 201This example shows how to clear all the mappings that are configured on the switch port:
Router(config-if)# no switchport vlan mapping allRelated Commands
switchport vlan mapping enable
To enable VLAN mapping per switch port, use the switchport vlan mapping enable command in interface configuration mode. To disable VLAN mapping per switch port, use the no form of this command.
switchport vlan mapping enable
no switchport vlan mapping enable
Syntax Description
This command has no arguments or keywords.
Defaults
VLAN mapping is disabled on all switch ports.
Command Modes
Interface configuration
Command History
12.2(17b)SXA
Support for this command was introduced on the Supervisor Engine 720.
12.2(33)SRA
This command was integrated into Cisco IOS Release 12.2(33)SRA.
Usage Guidelines
This command is not supported on Cisco 7600 series routers that are configured with a Supervisor Engine 2.
Note
The switchport vlan mapping enable command enables or disables VLAN-mapping lookup in the hardware regardless of whether the mapping is configured by the global VLAN mapping command or the switchport VLAN mapping command.
This command is useful on the hardware that supports VLAN mapping per ASIC only because you can turn on or off VLAN translation selectively on ports that are connected to the same port ASIC.
Examples
This example shows how to enable VLAN mapping per switch port:
Router(config-if)# switchport vlan mapping enableThis example shows how to disable VLAN mapping per switch port:
Router(config-if)# no switchport vlan mapping enableRelated Commands
switchport voice vlan
To configure a voice VLAN on a multiple-VLAN access port, use the switchport voice vlan command in interface configuration mode. To remove the voice VLAN from the switch port, use the no form of the command.
switchport voice vlan {vlan-id | dot1p | none | untagged}
no switchport voice vlan
Syntax Description
Defaults
The switch default is to not automatically configure the telephone (none).
The Cisco IP 7960 telephone default is to generate an 802.1Q/802.1P frame.
Command Modes
Interface configuration
Command History
Usage Guidelines
This command does not create a voice VLAN. You can create a voice VLAN in VLAN-configuration mode by entering the vlan (global configuration mode) command. If you configure both the native VLAN and the voice VLAN in the VLAN database and set the switch port to multiple-VLAN access mode, this command brings up the switch port as operational.
If you enter a voice VLAN identifier, the switch port sends CDP packets that configure the IP phone to transmit voice traffic in the voice VLAN in 802.1Q frames that are tagged with a Layer 2 CoS value.The default Layer 2 CoS is 5. The default Layer 3 IP-precedence value is 5.
If you enter dot1p, the switch port sends CDP packets that configure the IP phone to transmit voice traffic in the default VLAN in 802.1p frames that are tagged with a Layer 2 CoS value.
If you enter none, the switch port does not send CDP packets with VVID TLVs.
If you enter untagged, the switch port is enabled to receive untagged packets only.
Examples
This example shows how to create an operational multiple-VLAN access port with VLAN 101 as the voice VLAN:
Router(config-if)# switchportRouter(config-if)# switchport mode accessRouter(config-if)# switchport access vlan 100Router(config-if)# switchport voice vlan 101Router(config-if)This example shows how to change the multiple-VLAN access port to a normal access port:
Router(config-if)# interface fastethernet5/1Router(config-if)# no switchport voice vlanRouter(config-if)Related Commands
switchport access vlan
Sets the VLAN when the interface is in access mode.
switchport mode
Sets the interface type.
sync-restart-delay
To set the synchronization-restart delay timer to ensure accurate status reporting, use the sync-restart-delay command in interface configuration mode. To disable the synchronization-restart delay timer, use the no form of this command.
sync-restart-delay timer
no sync-restart-delay timer
Syntax Description
Defaults
timer is 210 milliseconds.
Command Modes
Interface configuration
Command History
Usage Guidelines
This command is supported on Gigabit Ethernet fiber ports only.
The status register records the current status of the link partner.
Examples
This example shows how to set the Gigabit Ethernet synchronization-restart delay timer:
Router(config-if)# sync-restart-delay 2000Related Commands
show running-config
Displays the status and configuration of the module or Layer 2 VLAN.
syscon address
To specify the system controller for a managed shelf, use the syscon address command in global configuration mode. To stop the management of the shelf by the system controller, use the no form of this command.
syscon address ip-address password
no syscon address
Syntax Description
Command Default
No system controller is specified.
Command Modes
Global configuration
Command History
Usage Guidelines
This command is required in order for the shelf to be managed by the system controller.
Examples
The following example configures a shelf to be managed by a system controller at 10.2.3.4 using the password green:
Router# syscon address 10.2.3.4 greenRelated Commands
show syscon sdp
Displays information about the Shelf Discovery Protocol.
syscon source-interface
Specifies the interface to use for the source address in SDP packets.
syscon shelf-id
To specify a shelf ID for a managed shelf, use the syscon shelf-id command in global configuration mode. To remove the shelf ID, use the no form of this command.
syscon shelf-id number
no syscon shelf-id
Syntax Description
Command Default
No shelf ID is specified.
Command Modes
Global configuration
Command History
Usage Guidelines
Use this command to specify a shelf ID for a managed shelf. Some platforms, such as the Cisco AS5800, use other commands to assign a shelf ID. In these situations, do not specify a shelf ID with the syscon shelf-id command. Use the platform-specific command instead.
Examples
The following example configures a shelf ID of 5 for the managed shelf:
Router# syscon shelf-id 5Related Commands
show syscon sdp
Displays information about the Shelf Discovery Protocol.
syscon address
Specifies the system controller for a managed shelf.
syscon source-interface
To specify the interface to use for the source address in Shelf Discovery Protocol (SDP) packets, use the syscon source-interface command in global configuration mode. To return to the default source interface for a packet (the interface that sent the packet from the shelf), use the no form of this command.
syscon source-interface type number
no syscon source-interface
Syntax Description
Command Default
SDP packets use the IP address of the output interface.
Command Modes
Global configuration
Command History
Usage Guidelines
Use this command to ensure that all SDP packets sent by the managed shelf have the same source IP address.
Examples
The following example configures a shelf to use the IP address of Ethernet interface 99/1/0:
Router# syscon source-address Ethernet99/1/0Related Commands
show syscon sdp
Displays information about the Shelf Discovery Protocol.
syscon shelf-id
Specifies a shelf ID for a managed shelf.
system flowcontrol bus
To set the FIFO overflow error count, use the system flowcontrol bus command in global configuration mode. To return to the original FIFO threshold settings, use the no form of this command.
[default] system flowcontrol bus {auto | on}
no system flowcontrol bus
Syntax Description
Defaults
auto
Command Modes
Global configuration
Command History
Usage Guidelines
Note
Examples
This example shows how to monitor the FIFO overflow error count and send a warning message if the FIFO overflow error count exceeds a configured error threshold in 5-second intervals:
Router(config)# system flowcontrol bus autoThis example shows how to specify the original FIFO threshold settings:
Router(config)# system flowcontrol bus onsystem jumbomtu
To set the maximum size of the Layer 2 and Layer 3 packets, use the system jumbomtu command in global configuration mode. To revert to the default MTU setting, use the no form of this command.
system jumbomtu mtu-size
no system jumbomtu
Syntax Description
Defaults
mtu-size is 9216 bytes.
Command Modes
Global configuration
Command History
Usage Guidelines
The mtu-size parameter specifies the Ethernet packet size, not the total Ethernet frame size. The Layer 3 MTU is changed as a result of entering the system jumbomtu command.
The system jumbomtu command enables the global MTU for port ASICs. On a port ASIC after jumbo frames are enabled, the port ASIC accepts any size packet on the ingress side and checks the outgoing packets on the egress side. The packets on the egress side that exceed the global MTU are dropped by the port ASIC.
For example, if you have port A in VLAN 1 and Port B in VLAN 2, and if VLAN 1 and VLAN 2 are configured for mtu 9216 and you enter the system jumbomtu 4000 command, the packets that are larger than 4000 bytes are not transmitted out because Ports B and A drop anything larger than 4000 bytes.
Examples
This example shows how to set the global MTU size to 1550 bytes:
Router(config)# system jumbomtu 1550This example shows how to revert to the default MTU setting:
Router(config)# no system jumbomtuRelated Commands
mtu
Adjusts the maximum packet size or MTU size.
show interfaces
Displays traffic that is seen by a specific interface.
show system jumbomtu
Displays the global MTU setting.
