Table of Contents

2

spanning-tree

Use the spanning-tree command to enable STP on a per-VLAN basis. Use the no form of this command to disable STP.

Syntax Description

stp-list

VLAN number; valid values are from 1 to 1005.

Defaults

The default is STP is enabled.

Command Modes

Interface configuration mode.

Usage Guidelines

When disabliing or reenabling STP, you must specify each VLAN you want to disable on a single command line.

When an STP VLAN is disabled and then enabled, all assigned VLANs continue to be its members. However, all spanning tree bridge parameters are returned to default settings.

Examples

This example shows how to disable STP on VLANs 1001 to 1004:

Router (config-if)# no spanning-tree vlan 1001
Router (config-if)# no spanning-tree vlan 1002
Router (config-if)# no spanning-tree vlan 1003
Router (config-if)# no spanning-tree vlan 1004
Router (config-if)# 
 

This example shows how to reenable STP on VLANs 1001 to 1004:

Router (config-if)# spanning-tree vlan 1001
Router (config-if)# spanning-tree vlan 1002
Router (config-if)# spanning-tree vlan 1003
Router (config-if)# spanning-tree vlan 1004
Router(config-if)# 

Related Commands

spanning-tree cost
spanning-tree port-priority
spanning-tree portfast (global configuration mode)
spanning-tree portfast (interface configuration mode)
spanning-tree uplinkfast
spanning-tree vlan

spanning-tree backbonefast

Use the spanning-tree backbonefast global configuration command to enable the BackboneFast feature on the specified spanning tree VLANs. Use the no form of the command to disable BackboneFast.

Syntax Description

This command has no arguments or keywords.

Defaults

The default is BackboneFast is disabled.

Command Modes

Global configuration mode.

Usage Guidelines

BackboneFast should be enabled on all Catalyst 6000 family switches to allow the detection of indirect link failures in order to start spanning tree reconfiguration sooner.

Router(config)# spanning-tree backbonefast vlan all ethernet 
Router(config)#

spanning-tree
spanning-tree cost
spanning-tree port-priority
spanning-tree portfast (global configuration mode)
spanning-tree portfast (interface configuration mode)
spanning-tree uplinkfast
spanning-tree vlan

spanning-tree cost

Use the spanning-tree cost command to set the path cost of the interface for STP calculations. Use the no form of this command to revert to the default value.

Syntax Description

cost	Path cost; valid values are from 1 to 65535.

Defaults

The default path cost is computed from the interface's bandwidth setting; 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 mode.

Usage Guidelines

When you configure the cost, higher values indicate higher costs. This range applies regardless of the protocol type specified.

Router(config)# interface ethernet 2/0
Router(config-if)# spanning-tree cost 250

spanning-tree
spanning-tree port-priority
spanning-tree portfast (global configuration mode)
spanning-tree portfast (interface configuration mode)
spanning-tree uplinkfast
spanning-tree vlan

spanning-tree portfast (global configuration mode)

Use the spanning-tree portfast command 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 no form of this command to disable PortFast mode.

Syntax Description

bpduguard

Keyword to enable PortFast BPDU guard on this switch.

Defaults

The default is PortFast is disabled.

Command Modes

Global configuration mode.

Usage Guidelines

This feature should only be used with interfaces that connect to end stations; otherwise, an accidental topology loop could cause a data packet loop and disrupt switch and network operation.

An interface with PortFast mode enabled is moved directly to the spanning tree forwarding state when linkup occurs without waiting the standard forward-time delay.

Examples

This example shows how to enable PortFast mode:

Router(config)# spanning-tree portfast bpduguard
Router(config)#

Related Commands

spanning-tree
spanning-tree cost
spanning-tree port-priority
spanning-tree portfast (interface configuration mode)
spanning-tree uplinkfast
spanning-tree vlan

spanning-tree portfast (interface configuration mode)

Use the spanning-tree portfast command 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 no form of this command to disable PortFast mode.

Syntax Description

This command has no argurments or keywords.

Defaults

The default is PortFast is disabled.

Command Modes

Interface configuration mode.

Usage Guidelines

This feature should be used only with interfaces that connect to end stations; otherwise, an accidental topology loop could cause a data packet loop and disrupt switch and network operation.

An interface with PortFast mode enabled is moved directly to the spanning tree forwarding state when linkup occurs without waiting the standard forward-time delay.

Examples

This example shows how to enable PortFast mode:

Router(config-if)# spanning-port portfast
Router(config-if)#

Related Commands

spanning-tree
spanning-tree cost
spanning-tree port-priority
spanning-tree portfast (global configuration mode)
spanning-tree uplinkfast
spanning-tree vlan

spanning-tree port-priority

Use the spanning-tree port-priority command to set an interface priority when two bridges tie for position as the root bridge. The priority you set breaks the tie. Use the no from of this command to revert to the default value.

Syntax Description

port_priority

Port priority; valid values are from 2 to 255.

Defaults

The default configuration is for IEEE is 128.

Command Modes

Interface configuration mode.

Examples

This example shows how to increase the likelihood that the spanning tree instance 20 will be chosen as the root-bridge on interface ethernet 2/0.

Router(config-if)# spanning-tree port-priority 0
Router(config-if)#

Related Commands

spanning-tree
spanning-tree cost
spanning-tree portfast (global configuration mode)
spanning-tree portfast (interface configuration mode)
spanning-tree uplinkfast
spanning-tree vlan

spanning-tree uplinkfast

Use the spanning-tree uplinkfast command to enable the UplinkFast feature. Use the no form of the command to disable UplinkFast.

Syntax Description

max-update-rate packets_per_second

(Optional) Keywords and variable to specify the maximum rate (in packets per second) at which update packets are sent; valid values are from 0 to 65535.

Defaults

The default is UplinkFast is disabled, and max-update-rate is 150 packets per second.

Command Modes

Global configuration mode.

Usage Guidelines

This command should be used only on access switches.

Router(config)# spanning-tree uplinkfast max-update-rate 200
Router(config)# 

spanning-tree
spanning-tree cost
spanning-tree port-priority
spanning-tree portfast (global configuration mode)
spanning-tree portfast (interface configuration mode)
spanning-tree vlan

spanning-tree vlan

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

Syntax Description

forward-time seconds	(Optional) Keyword and variable to set the STP forward delay time; valid values are from 4 to 30 seconds.
hello-time hello-time	(Optional) Keyword and variable to specify in seconds, the duration between the generation of configuration messages by the root switch; valid values are from 1 to 10 seconds.
max-age seconds	(Optional) Keyword to set the maximum number of seconds the information in a BPDU is valid; valid values are from 6 to 40 seconds.
priority priority	(Optional) Keyword to set the STP bridge priority; valid values are from 0 to 65535.
protocol protocol	(Optional) Keyword to set the STP. See the "" section for a list of valid values.
root primary	(Optional) Keywords to force this switch to be the root bridge.
root secondary	(Optional) Keywords to specify this switch act as the root switch should the primary root fail.
diameter net-diameter	(Optional) Keyword and variable to specify the maximum number of bridges between any two points of attachment of end stations; valid values are from 2 through 7.

Defaults

The defaults are:

• forward-time---15 seconds

• hello-time---2 seconds

• max-age---20 seconds

• priority---The default with IEEE STP enabled is 32768; with STP enabled is 128.

• protocol---ieee

• root---No STP root

Command Modes

Global configuration mode.

Usage Guidelines

When setting the max-age seconds, if a bridge does not hear BPDUs from the root bridge within the specified interval, it assumes that the network has changed and recomputes the spanning tree topology.

Router(config)# spanning-tree vlan 200 
Router(config)# 
 

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

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

spanning-tree
spanning-tree cost
spanning-tree port-priority
spanning-tree portfast (global configuration mode)
spanning-tree portfast (interface configuration mode)
spanning-tree uplinkfast

speed

Use the speed command to configure the interface speed. Use the no form of this command to disable a speed setting.

Syntax Description

10	(Optional) Keyword to configure the interface to transmit at 10 Mbps.
100	(Optional) Keyword to configure the interface to transmit at 100 Mbps.
auto	(Optional) Keyword to enable the auto-negotiation capability.
nonegotiate	(Optional) Keyword to enable the nonegotiate feature.

Defaults

See Table 2-9 for a list of default settings.

Command Modes

Interface configuration mode.

Usage Guidelines

Table 2-9 lists the supported command options by interface.

Table 2-9: Supported speed Command Options

Interface Type	Supported Syntax	Default Setting	Usage Guidelines
10/100-Mbps module (WS-X6248-RJ-45)	speed [10 | 100 | auto]	auto	If the speed is set to auto, you will not be able to set duplex. If the speed is set to 10 or 100, and you do not configure the duplex setting, the duplex is set to half.
100-Mbps fiber modules (WS-X6224- 100FX-MT)	Not supported.	Not supported.
Gigabit Ethernet Interface (WS-X6408-GBIC)	speed nonegotiate	Nonegotiate is disabled.
10-Mbps ports	Not supported.	Not supported.

If you decide to configure the interface speed and duplex commands manually, and enter a value other than speed auto (for example, 10 or 100 Mbps), ensure that you configure the connecting interface speed command to a matching speed but do not use the auto parameter.

When manually configuring the interface speed to either 10 or 100 Mbps, the switch prompts you to also configure duplex mode on the interface.

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Note Catalyst 6000 family switches cannot automatically negotiate interface speed and duplex mode if either connecting interface is configured to a value other than auto.

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Caution Changing the interface speed and duplex mode configuration might shut down and reenable the interface during the reconfiguration.

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Table 2-10 describes the system's performance for different combinations of the duplex and speed modes. The specified duplex command configured with the specified speed command produces the resulting system action.

Table 2-10: Relationship Between duplex and speed Commands

duplex Command	speed Command	Resulting System Action
duplex half or duplex full	speed auto	Autonegotiates both speed and duplex modes
duplex half	speed 10	Forces 10 Mbps and half duplex
duplex full	speed 10	Forces 10 Mbps and full duplex
duplex half	speed 100	Forces 100 Mbps and half duplex
duplex full	speed 100	Forces 100 Mbps and full duplex

Router(config-if)# speed 100
Router(config-if)#

duplex
interface (refer to Cisco IOS documentation)
show controllers (refer to Cisco IOS documentation)
show interfaces (refer to Cisco IOS documentation)

stack-mib portname

Use the stack-mib command to specify a name string for a port.

Syntax Description

portname

Descriptive text describing the function of the interface.

Defaults

This command has no default setting.

Command Modes

Interface configuration mode.

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 portal_to_paradise
Router(config-if)#

switchport

Use the switchport command to modify the switching characteristics of the Layer 2-switched interface. Use the no form of this command (without parameters) to return the interface to the routed-interface status and cause all further Layer 2 configuration to be erased.

Syntax Description

access vlan vlan-id	Keywords and variable to set the VLAN when the interface is in access mode; valid values are from 1 to 1005.
access vlan dynamic	Keyword to specify that the access mode VLAN is dependent on the VMPS protocol.
multi vlan vlan-list	Keywords and variable to specify the list of VLANs when the interface is in "multiprotocol" trunk mode. See the "" section for formatting guidelines.
nonegotiate	Keyword to specify DISL/DTP negotiation packets will not be sent on the interface.

Defaults

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

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

Command Modes

Interface configuration mode.

Usage Guidelines

Entering the no switchport command shuts the port down and then reenables it, which may generate messages on the device to which the port is connected.

The no form of the switchport access command resets the access mode VLAN to the appropriate default VLAN for the device. The no form of the switchport nonegotiate command removes nonegotiate status.

When using the nonegotiate keyword, DISL/DTP negotiation packets will not be sent on the interface. The device will trunk or not trunk according to the mode parameter given: access or trunk. This command will return an error if you attempt to execute it in dynamic (auto or desirable) mode. This command is unnecessary and will be ignored if you attempt to execute it in in multi mode.

Examples

This example shows how to cause the port interface to cease operating as a Cisco-routed port and convert to a Layer 2-switched interface:

Router(config-if)# switchport
Router(config-if)#

---

Note The above command is not used on platforms that do not support Cisco-routed ports. All physical ports on such platforms are assumed to be Layer 2-switched interfaces.

---

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 when in access mode:

Router(config-if)# switchport access vlan 2
Router(config-if)#
 

This example shows how to cause a port interface that has already been configured as a switched interface to encapsulate in 802.1Q trunking format regardless of its default trunking format when in trunking mode:

Router(config-if)# switchport trunk encapsulation dot1q
Router(config-if)#
 

This example shows how to cause a port interface that has already been configured as a switched interface to negotiate trunking mode with its peer using the desirable parameter regardless of its DISL/DTP default parameters:

Router(config-if)# switchport dynamic desirable
Router(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 nonegotiate
Router(config-if)#

Related Commands

show interfaces switchport

switchport broadcast

Use the switchport broadcast command to set the broadcast suppression level on the interface. Use the no form of this command to disable broadcast suppression.

Syntax Description

level

Broadcast suppression level; valid values are from 0 to 100 percent.

Defaults

The default is broadcast suppression is disabled.

Command Modes

Interface configuration mode.

Usage Guidelines

The broadcast suppression level is entered as a percentage of the total bandwidth. A threshold value of 100 percent means that no limit is placed on broadcast traffic.

Examples

This example shows how to enable bandwidth-based broadcast suppression:

Router(config-if)# switchport broadcast 75 
Router(config-if)# 
 

This example shows how to disable bandwidth-based broadcast suppression:

Router(config-if)# no switchport broadcast 75 
Router(config-if)# 

Related Commands

switchport
show interfaces switchport
show broadcast interface (refer to Cisco IOS documentation)

switchport mode

Use the switchport mode command to set the Layer 2 interface type. Use the no form of the command to reset the mode to the appropriate default mode for the device.

Syntax Description

access	Keyword to specify a nontrunking, nontagged single VLAN Layer 2 interface.
trunk	Keyword to specify a trunking VLAN Layer 2 interface.
multi	Keyword to specify a nontagged, "multiprotocol" trunk (VLAN is determined by protocol type).
dynamic auto	Keywords to specify that the interface convert the link to a trunk link.
dynamic desirable	Keywords to specify that the interface actively attempt to convert the link to a trunk link.

Defaults

The default mode is dependent on the platform; it should either be dynamic auto for platforms that are intended for wiring closets or dynamic desirable for platforms that are intended as backbone switches.

Command Modes

Interface configuration mode.

Usage Guidelines

The multi keyword is not supported on some platforms. This mode implicitly turns off DISL and DTP protocols.

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.

Examples

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

Router(config-if)# switchport mode dynamic desirable
Router(config-if)#

Related Commands

switchport
show interfaces switchport

switchport protocol

Use the switchport protocol command to modify the protocol filtering mode for each included protocol when the port is in access mode. Use the no form of this command to disable protocol filtering.

Syntax Description

ip | ipx | appletalk	Keyword to specify the protocol filter type.
other	Keyword to specify protocols other than IP, IPX, and AppleTalk.
off	Keyword to cause packets of the specified protocols to be filtered.
on	Keyword to cause packets of the specified protocol to transmit to and from the interface.
auto	Keyword to cause packets of the specified protocol to transmit to and from the interface only if a packet of that protocol has been received by the device within the most recent 60 minutes (the aging time).

Defaults

The default is on for all other protocol types.

Command Modes

Interface configuration mode.

Usage Guidelines

You must use the protocol-filtering command to enable protocol filtering before setting the filtering mode.

The switchport protocol command is supported on platforms that support EARL 2 mode 1 address filtering only.

The no form of the command is synonymous with off.

Examples

This example shows how to set the protocol membership of an interface to receive IPX packets only:

Router(config-if)# switchport protocol appletalk off
Router(config-if)# switchport protocol ip off
Router(config-if)# switchport protocol ipx on

Related Commands

protocol-filtering
switchport
show interfaces switchport

switchport trunk

Use the switchport trunk commands to set the trunk characteristics when the interface is in trunking mode. Use the no form of this command to reset all of the trunking characteristics back to the original defaults.

Syntax Description

encapsulation isl	Keywords to set the trunk encapsulation format to ISL.
encapsulation dot1q	Keywords to set the trunk encapsulation format to 802.1Q.
encapsulation negotiate	Keywords to specify that if DISL and DTP negotiation do not resolve the encapsulation format, ISL is the selected format.
native vlan vlan-id	Keywords and variable to set the native VLAN for the trunk in 802.1Q trunking mode.
allowed vlan vlan-list	Keywords and variable to set the list of allowed VLANs that transmit this interface in tagged format when in trunking mode. See the "" section for vlan-list formatting guidelines.
pruning vlan vlan-list	Keywords and variable to set the list of VLANs that are enabled for VTP pruning when in trunking mode. See the "" section for vlan-list formatting guidelines.

Defaults

The default encapsulation type is dependent on the platform or interface hardware itself.

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

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

Command Modes

Interface configuration mode.

Usage Guidelines

The switchport trunk encapsulation command is supported only for platforms and interface hardware that can support both ISL and 802.1Q formats.

Router(config-if)# switchport trunk encapsulation dot1q
Router(config-if)#

show interfaces switchport

Posted: Thu Jul 20 15:29:58 PDT 2000
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