Usage Guidelines

For Layer 2 EtherChannels, the channel-group command automatically creates the port-channel interface when the channel group gets its first physical port. You do not have to use the interface port-channel command in global configuration mode to manually create a port-channel interface. If you create the port-channel interface first, the channel-group-number can be the same as the port-channel-number , or you can use a new number. If you use a new number, the channel-group command dynamically creates a new port channel.

Although it is not necessary to disable the IP address that is assigned to a physical port that is part of a channel group, we strongly recommend that you do so.

You create Layer 3 port channels by using the interface port-channel command followed by the no switchport interface configuration command. Manually configure the port-channel logical interface before putting the interface into the channel group.

After you configure an EtherChannel, configuration changes that you make on the port-channel interface apply to all the physical ports assigned to the port-channel interface. Configuration changes applied to the physical port affect only the port where you apply the configuration. To change the parameters of all ports in an EtherChannel, apply configuration commands to the port-channel interface, for example, spanning-tree commands or commands to configure a Layer 2 EtherChannel as a trunk.

Active mode places a port into a negotiating state in which the port initiates negotiations with other ports by sending LACP packets. A channel is formed with another port group in either the active or passive mode.

Auto mode places a port into a passive negotiating state in which the port responds to PAgP packets it receives but does not start PAgP packet negotiation. A channel is formed only with another port group in desirable mode. When auto is enabled, silent operation is the default.

Desirable mode places a port into an active negotiating state in which the port starts negotiations with other ports by sending PAgP packets. An EtherChannel is formed with another port group that is in the desirable or auto mode. When desirable is enabled, silent operation is the default.

If you do not specify non-silent with the auto or desirable mode, silent is assumed. The silent mode is used when the switch is connected to a device that is not PAgP-capable and rarely, if ever, sends packets. An example of a silent partner is a file server or a packet analyzer that is not generating traffic. In this case, running PAgP on a physical port prevents that port from ever becoming operational. However, it allows PAgP to operate, to attach the port to a channel group, and to use the port for transmission. Both ends of the link cannot be set to silent.

In on mode, a usable EtherChannel exists only when both connected port groups are in the on mode.

Caution

Use care when using the on mode. This is a manual configuration, and ports on both ends of the EtherChannel must have the same configuration. If the group is misconfigured, packet loss or spanning-tree loops can occur.

Passive mode places a port into a negotiating state in which the port responds to received LACP packets but does not initiate LACP packet negotiation. A channel is formed only with another port group in active mode.

Do not configure an EtherChannel in both the PAgP and LACP modes. EtherChannel groups running PAgP and LACP can coexist on the same switch or on different switches in the stack (but not in a cross-stack configuration). Individual EtherChannel groups can run either PAgP or LACP, but they cannot interoperate.

If you set the protocol by using the channel-protocol interface configuration command, the setting is not overridden by the channel-group interface configuration command.

Do not configure a port that is an active or a not-yet-active member of an EtherChannel as an IEEE 802.1x port. If you try to enable IEEE 802.1x authentication on an EtherChannel port, an error message appears, and IEEE 802.1x authentication is not enabled.

Do not configure a secure port as part of an EtherChannel or configure an EtherChannel port as a secure port.

For a complete list of configuration guidelines, see the “Configuring EtherChannels” chapter in the software configuration guide for this release.

Caution

Do not enable Layer 3 addresses on the physical EtherChannel ports. Do not assign bridge groups on the physical EtherChannel ports because it creates loops.

Usage Guidelines

Use the channel-protocol command only to restrict a channel to LACP or PAgP. If you set the protocol by using the channel-protocol command, the setting is not overridden by the channel-group command in interface configuration mode.

You must use the channel-group command in interface configuration mode to configure the EtherChannel parameters. The channel-group command also can set the mode for the EtherChannel.

You cannot enable both the PAgP and LACP modes on an EtherChannel group.

PAgP and LACP are not compatible; both ends of a channel must use the same protocol.

You cannot configure PAgP on cross-stack configurations.

Usage Guidelines

Use this command to clear protocol tunnel counters on the switch or on the specified interface.

Usage Guidelines

You can clear all counters by using the clear lacp counters command, or you can clear only the counters for the specified channel group by using the clear lacp channel-group-number counters command.

Usage Guidelines

You can clear all counters by using the clear pagp counters command, or you can clear only the counters for the specified channel group by using the clear pagp channel-group-number counters command.

Usage Guidelines

If the interface-id value is not specified, spanning-tree counters are cleared for all interfaces.

Usage Guidelines

A device running the rapid per-VLAN spanning-tree plus (rapid-PVST+) protocol or the Multiple Spanning Tree Protocol (MSTP) supports a built-in protocol migration method that enables it to interoperate with legacy IEEE 802.1D devices. If a rapid-PVST+ or an MSTP device receives a legacy IEEE 802.1D configuration bridge protocol data unit (BPDU) with the protocol version set to 0, the device sends only IEEE 802.1D BPDUs on that port. A multiple spanning-tree (MST) device can also detect that a port is at the boundary of a region when it receives a legacy BPDU, an MST BPDU (Version 3) associated with a different region, or a rapid spanning-tree (RST) BPDU (Version 2).

The device does not automatically revert to the rapid-PVST+ or the MSTP mode if it no longer receives IEEE 802.1D BPDUs because it cannot learn whether the legacy switch has been removed from the link unless the legacy switch is the designated switch. Use the clear spanning-tree detected-protocols command in this situation.

Usage Guidelines

The undebug etherchannel command is the same as the no debug etherchannel command.

Note	Although the linecard keyword is displayed in the command-line help, it is not supported.

Usage Guidelines

The undebug etherchannel command is the same as the no debug etherchannel command.

Usage Guidelines

The undebug pagp command is the same as the no debug pagp command.

Usage Guidelines

The undebug platform pm command is the same as the no debug platform pm command.

Usage Guidelines

The undebug platform udld command is the same as the no debug platform udld command.

When you enable debugging on a switch stack, it is enabled only on the active switch. To enable debugging on a stack member, you can start a session from the active switch by using the session switch-number command in privileged EXEC mode. Then enter the debug command at the command-line prompt of the stack member.

Usage Guidelines

The undebug spanning-tree command is the same as the no debug spanning-tree command.

When you enable debugging on a stack, it is enabled only on the active switch. To enable debugging on the standby switch, start a session from the active switch by using the session switch-number command in privileged EXEC mode. Enter the debug command at the command-line prompt of the standby switch.

To enable debugging on the standby switch without first starting a session on the active switch, use the remote command switch-number LINE command in privileged EXEC mode.

Usage Guidelines

The vlans vlan-range is entered as a single value or a range.

The mapping is incremental, not absolute. When you enter a range of VLANs, this range is added or removed to the existing instances.

Any unmapped VLAN is mapped to the CIST instance.

Usage Guidelines

For Layer 2 EtherChannels, you do not have to create a port-channel interface before assigning physical ports to a channel group. Instead, you can use the channel-group command in interface configuration mode, which automatically creates the port-channel interface when the channel group obtains its first physical port. If you create the port-channel interface first, the channel-group-number can be the same as the port-channel-number , or you can use a new number. If you use a new number, the channel-group command dynamically creates a new port channel.

You create Layer 3 port channels by using the interface port-channel command followed by the no switchport command in interface configuration mode. You should manually configure the port-channel logical interface before putting the interface into the channel group.

Only one port channel in a channel group is allowed.

Caution

When using a port-channel interface as a routed port, do not assign Layer 3 addresses on the physical ports that are assigned to the channel group.

Caution

Do not assign bridge groups on the physical ports in a channel group used as a Layer 3 port channel interface because it creates loops. You must also disable spanning tree.

Follow these guidelines when you use the interface port-channel command:

• If you want to use the Cisco Discovery Protocol (CDP), you must configure it on the physical port and not on the port channel interface.

• Do not configure a port that is an active member of an EtherChannel as an IEEE 802.1x port. If IEEE 802.1x is enabled on a not-yet active port of an EtherChannel, the port does not join the EtherChannel.

For a complete list of configuration guidelines, see the “Configuring EtherChannels” chapter in the software configuration guide for this release.

Usage Guidelines

You can enable tunneling for Cisco Discovery Protocol (CDP), Spanning Tree Protocol (STP), or VLAN Trunking Protocol (VTP) packets. You can also enable point-to-point tunneling for Port Aggregation Protocol (PAgP), Link Aggregation Control Protocol (LACP), or UniDirectional Link Detection (UDLD) packets.

You must enter this command, with or without protocol types, to tunnel Layer 2 packets.

If you enter this command for a port channel, all ports in the channel must have the same configuration.

Layer 2 protocol tunneling across a service-provider network ensures that Layer 2 information is propagated across the network to all customer locations. When protocol tunneling is enabled, protocol packets are encapsulated with a well-known Cisco multicast address for transmission across the network. When the packets reach their destination, the well-known MAC address is replaced by the Layer 2 protocol MAC address.

You can enable Layer 2 protocol tunneling for CDP, STP, and VTP individually or for all three protocols.

In a service-provider network, you can use Layer 2 protocol tunneling to enhance the creation of EtherChannels by emulating a point-to-point network topology. When protocol tunneling is enabled on the service-provider switch for PAgP or LACP, remote customer switches receive the protocol data units (PDUs) and can negotiate automatic creation of EtherChannels.

To enable tunneling of PAgP, LACP, and UDLD packets, you must have a point-to-point network topology. To decrease the link-down detection time, you should also enable UDLD on the interface when you enable tunneling of PAgP or LACP packets.

You can enable point-to-point protocol tunneling for PAgP, LACP, and UDLD individually or for all three protocols.

Caution

PAgP, LACP, and UDLD tunneling is only intended to emulate a point-to-point topology. An erroneous configuration that sends tunneled packets to many ports could lead to a network failure.

Enter the shutdown-threshold keyword to control the number of protocol packets per second that are received on an interface before it shuts down. When no protocol option is specified with the keyword, the threshold is applied to each of the tunneled Layer 2 protocol types. If you also set a drop threshold on the interface, the shutdown-threshold value must be greater than or equal to the drop-threshold value.

When the shutdown threshold is reached, the interface is error-disabled. If you enable error recovery by entering the errdisable recovery cause l2ptguard global configuration command, the interface is brought out of the error-disabled state and allowed to retry the operation again when all the causes have timed out. If the error recovery function is not enabled for l2ptguard , the interface stays in the error-disabled state until you enter the shutdown and no shutdown interface configuration commands.

Enter the drop-threshold keyword to control the number of protocol packets per second that are received on an interface before it drops packets. When no protocol option is specified with a keyword, the threshold is applied to each of the tunneled Layer 2 protocol types. If you also set a shutdown threshold on the interface, the drop-threshold value must be less than or equal to the shutdown-threshold value.

When the drop threshold is reached, the interface drops Layer 2 protocol packets until the rate at which they are received is below the drop threshold.

The configuration is saved in NVRAM.

For more information about Layer 2 protocol tunneling, see the software configuration guide for this release.

Usage Guidelines

Prior to entering the lacp fast-switchover command, you must ensure the following:

• The port channel protocol type is LACP.

• The lacp max-bundle 1 command has been entered on the port channel. Note that the lacp fast-switchover command will not affect the lacp max-bundle command.

Prior to entering the lacp fast-switchover dampening command, you must ensure the following:

• The port channel protocol type is LACP.

• The lacp max-bundle 1 and lacp fast-switchover commands have been entered on the port channel.

When you enable LACP 1:1 link redundancy, based on the system priority and port priority, the port with the higher system priority chooses one link as the active link and the other link as the standby link (lower the LACP port priority, higher the preference, and lower the LACP system priority, higher the preference). In the case of the LACP 1:1 Redundancy feature, when the active link fails, the standby link is selected as the new active link without taking down the port channel. When the original active link recovers, it reverts to its active link status. During this changeover, the port channel is also up.

In the case of LACP 1:1 Hot Standby Dampening feature, a timer is configured that delays the switchover back to the higher priority port after it becomes active.

Note	We recommend that you configure only two ports (one active and one hot standby) in the bundle, for optimum performance. LACP 1:1 redundancy must be enabled at both ends of the LACP EtherChannel. LACP 1:1 redundancy and dampening work only on LACP port channels.

Usage Guidelines

An LACP channel group can have up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in hot-standby mode. When there are more than eight ports in an LACP channel group, the device on the controlling end of the link uses port priorities to determine which ports are bundled into the channel and which ports are put in hot-standby mode. Port priorities on the other device (the noncontrolling end of the link) are ignored.

The lacp max-bundle command must specify a number greater than the number specified by the port-channel min-links command.

Use the show etherchannel summary command in privileged EXEC mode to see which ports are in the hot-standby mode (denoted with an H port-state flag in the output display).

Usage Guidelines

The lacp port-priority command in interface configuration mode determines which ports are bundled and which ports are put in hot-standby mode when there are more than eight ports in an LACP channel group.

An LACP channel group can have up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode.

In port-priority comparisons, a numerically lower value has a higher priority: When there are more than eight ports in an LACP channel group, the eight ports with the numerically lowest values (highest priority values) for LACP port priority are bundled into the channel group, and the lower-priority ports are put in hot-standby mode. If two or more ports have the same LACP port priority (for example, they are configured with the default setting of 65535), then an internal value for the port number determines the priority.

Note	The LACP port priorities are only effective if the ports are on the device that controls the LACP link. See the lacp system-priority command in global configuration mode for determining which device controls the link.

Use the show lacp internal command in privileged EXEC mode to display LACP port priorities and internal port number values.

For information about configuring LACP on physical ports, see the configuration guide for this release.

Usage Guidelines

Use this command to modify the duration of LACP timeout. The LACP timeout value on Cisco switch is three times the LACP rate that is configured on the interface. Using the lacp ratecommand, you can select the LACP timeout value for a switch to be either 90 seconds or 3 seconds.

This command is supported only on LACP-enabled interfaces.

Usage Guidelines

The lacp system-priority command determines which device in an LACP link controls port priorities.

An LACP channel group can have up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in standby mode. When there are more than eight ports in an LACP channel group, the device on the controlling end of the link uses port priorities to determine which ports are bundled into the channel and which ports are put in hot-standby mode. Port priorities on the other device (the noncontrolling end of the link) are ignored.

In priority comparisons, numerically lower values have a higher priority. Therefore, the system with the numerically lower value (higher priority value) for LACP system priority becomes the controlling system. If both devices have the same LACP system priority (for example, they are both configured with the default setting of 32768), the LACP system ID (the device MAC address) determines which device is in control.

The lacp system-priority command applies to all LACP EtherChannels on the device.

Use the show etherchannel summary command in privileged EXEC mode to see which ports are in the hot-standby mode (denoted with an H port-state flag in the output display).

Usage Guidelines

You can error-disable either the source port or the destination port depending on your requirement. When the loopdetect command is configured without any of the keywords or variables, the feature is enabled and the destination port is error-disabled when a loop is detected.We recommend that you error-disable the source port to better control traffic flow to and from your network.

The loopdetect action syslog command displays only a system message and does not error-disable the configured port. The no loopdetect action syslog command reverts the system to the last configured option.

Usage Guidelines

Two or more devices with the same VLAN mapping and configuration version number are considered to be in different MST regions if the region names are different.

Note	Be careful when using the name command to set the name of an MST region. If you make a mistake, you can put the device in a different region. The configuration name is a case-sensitive parameter.

Usage Guidelines

The learn method must be configured the same at both ends of the link.

The device supports address learning only on aggregate ports even though the physical-port keyword is provided in the command-line interface (CLI). The pagp learn-method and the pagp port-priority commands in interface configuration mode have no effect on the device hardware, but they are required for PAgP interoperability with devices that only support address learning by physical ports.

When the link partner to the device is a physical learner, we recommend that you configure the device as a physical-port learner by using the pagp learn-method physical-port command in interface configuration mode. We also recommend that you set the load-distribution method based on the source MAC address by using the port-channel load-balance src-mac command in global configuration mode. Use the pagp learn-method command in interface configuration mode only in this situation.

Usage Guidelines

The physical port with the highest priority that is operational and has membership in the same EtherChannel is the one selected for PAgP transmission.

The device supports address learning only on aggregate ports even though the physical-port keyword is provided in the command-line interface (CLI). The pagp learn-method and the pagp port-priority commands in interface configuration mode have no effect on the device hardware, but they are required for PAgP interoperability with devices that only support address learning by physical ports, such as the Catalyst 1900 switch.

When the link partner to the device is a physical learner, we recommend that you configure the device as a physical-port learner by using the pagp learn-method physical-port command in interface configuration mode. We also recommend that you set the load-distribution method based on the source MAC address by using the port-channel load-balance src-mac command in global configuration mode. Use the pagp learn-method command in interface configuration mode only in this situation.

Usage Guidelines

You must configure the PTP-property name using the ptp property command and configure a unicast IPv4 connection from a loopback interface using the transport unicast ipv4 local loopback command before connecting to a peer PTP-aware device.

Usage Guidelines

You can use the show etherchannel summary command in privileged EXEC mode to display the EtherChannel information.

Usage Guidelines

You can use the show etherchannel auto command in privileged EXEC mode to verify if the EtherChannel was created automatically.

Usage Guidelines

You can verify your setting by entering either the show running-config command in privileged EXEC mode or the show etherchannel load-balance command in privileged EXEC mode.

Usage Guidelines

You can verify your setting by entering either the show running-config command in privileged EXEC mode or the show etherchannel load-balance command in privileged EXEC mode.

Usage Guidelines

An LACP channel group can have up to 16 Ethernet ports of the same type. Up to eight ports can be active, and up to eight ports can be in hot-standby mode. When there are more than eight ports in an LACP channel group, the device on the controlling end of the link uses port priorities to determine which ports are bundled into the channel and which ports are put in hot-standby mode. Port priorities on the other device (the noncontrolling end of the link) are ignored.

The port-channel min-links command must specify a number a less than the number specified by the lacp max-bundle command.

Use the show etherchannel summary command in privileged EXEC mode to see which ports are in the hot-standby mode (denoted with an H port-state flag in the output display).

Usage Guidelines

Use this command for IEEE 1588 PTP profiles in IPv4 UDP transport mode only.

Usage Guidelines

You can configure more than one IPv4 unicast connection that connects to a different boundary clock under the same property name.

Usage Guidelines

Setting a port permanently ensures that the port remain as a primary (master) even if a clock connected to the port can be elected as grandmaster clock.

Note	The command ptp role primary must be used only on ports that are used as end nodes on a network that are connected to devices requiring synchronization.

Use the show ptp port interface_id command to verify if the port is set as primary (master).

Usage Guidelines

When you select an alternate port by entering an offset number, this number identifies the downstream neighbor port of an edge port. The primary edge port has an offset number of 1; positive numbers above 1 identify downstream neighbors of the primary edge port. Negative numbers identify the secondary edge port (offset number -1) and its downstream neighbors.

Note	Do not enter an offset value of 1 because that is the offset number of the primary edge port itself.

If you have configured a preempt delay time by entering the rep preempt delay seconds command in interface configuration mode and a link failure and recovery occurs, VLAN load balancing begins after the configured preemption time period elapses without another link failure. The alternate port specified in the load-balancing configuration blocks the configured VLANs and unblocks all the other segment ports. If the primary edge port cannot determine the alternate port for VLAN balancing, the default action is no preemption.

Each port in a segment has a unique port ID. To determine the port ID of a port, enter the show interfaces interface-id rep detail command in privileged EXEC mode.

Usage Guidelines

While configuring REP configurable timers, we recommend that you configure the REP LSL number of retries first and then configure the REP LSL age-out timer value.

Usage Guidelines

The rep lsl-retries command is used to configure the number of retries before the REP link is disabled. While configuring REP configurable timers, we recommend that you configure the REP LSL number of retries first and then configure the REP LSL age-out timer value.

Usage Guidelines

Enter this command on the REP primary edge port.

Enter this command and configure a preempt time delay for VLAN load balancing to be automatically triggered after a link failure and recovery.

If VLAN load balancing is configured after a segment port failure and recovery, the REP primary edge port starts a delay timer before VLAN load balancing occurs. Note that the timer restarts after each link failure. When the timer expires, the REP primary edge port alerts the alternate port to perform VLAN load balancing (configured by using the rep block port command in interface configuration mode) and prepares the segment for the new topology. The configured VLAN list is blocked at the alternate port, and all other VLANs are blocked at the primary edge port.

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

Usage Guidelines

Enter this command on the segment, which has the primary edge port on the device.

Ensure that all the other segment configuratios are completed before setting preemption for VLAN load balancing. When you enter the rep preempt segment segment-id command, a confirmation message appears before the command is executed because preemption for VLAN load balancing can disrupt the network.

If you do not enter the rep preempt delay seconds command in interface configuration mode on the primary edge port to configure a preemption time delay, the default configuration is to manually trigger VLAN load balancing on the segment.

Enter the show rep topology command in privileged EXEC mode to see which port in the segment is the primary edge port.

If you do not configure VLAN load balancing, entering the rep preempt segment segment-id command results in the default behavior, that is, the primary edge port blocks all the VLANs.

You can configure VLAN load balancing by entering the rep block port command in interface configuration mode on the REP primary edge port before you manually start preemption.

Usage Guidelines

REP ports must be a Layer 2 IEEE 802.1Q port or a 802.1AD port. You must configure two edge ports on each REP segment, a primary edge port and a secondary edge port.

If REP is enabled on two ports on a device, both the ports must be either regular segment ports or edge ports. REP ports follow these rules:

• If only one port on a device is configured in a segment, that port should be an edge port.

• If two ports on a device belong to the same segment, both the ports must be regular segment ports.

• If two ports on a device belong to the same segment, and one is configured as an edge port and one as a regular segment port (a misconfiguration), the edge port is treated as a regular segment port.

Caution

REP interfaces come up in a blocked state and remain in a blocked state until notified that it is safe to unblock. Be aware of this to avoid sudden connection losses.

When REP is enabled on an interface, the default is for that port to be a regular segment port.

Usage Guidelines

You can verify your settings by entering the show interfaces rep detail command in privileged EXEC mode.

Usage Guidelines

Devices that have the same configuration but different revision numbers are considered to be part of two different regions.

Note	Be careful when using the revision command to set the revision number of the MST configuration because a mistake can put the switch in a different region.

Usage Guidelines

If you do not specify a channel group number, all channel groups are displayed.

In the output, the passive port list field is displayed only for Layer 3 port channels. This field means that the physical port, which is still not up, is configured to be in the channel group (and indirectly is in the only port channel in the channel group).

Usage Guidelines

Enter this command on a segment edge port to send STCNs to one or more segments or to an interface.

You can verify your settings by entering the show interfaces rep detail command in privileged EXEC mode.

Usage Guidelines

After enabling Layer 2 protocol tunneling on an access or IEEE 802.1Q tunnel port by using the l2protocol-tunnel interface configuration command, you can configure some or all of these parameters:

• Protocol type to be tunneled

• Shutdown threshold

• Drop threshold

If you enter the show l2protocol-tunnel interface command, only information about the active ports on which all the parameters are configured appears.

If you enter the show l2protocol-tunnel summary command, only information about the active ports on which some or all of the parameters are configured appears.

Usage Guidelines

You can enter any show lacp command to display the active channel-group information. To display specific channel information, enter the show lacp command with a channel-group number.

If you do not specify a channel group, information for all channel groups appears.

You can enter the channel-group-number to specify a channel group for all keywords except sys-id .

Usage Guidelines

You can enter any show pagp command to display the active channel-group information. To display the nonactive information, enter the show pagp command with a channel-group number.

Usage Guidelines

Use this command only when you are working directly with a technical support representative while troubleshooting a problem.

Do not use this command unless a technical support representative asks you to do so.

Usage Guidelines

Use this command only when you are working directly with your technical support representative while troubleshooting a problem.

Do not use this command unless your technical support representative asks you to do so.

Usage Guidelines

The number of VLAN mappings configured on each ASIC can be derived by summing up the total number of interfaces on each ASIC. The output of the show platform software fed active ifm mappings command displays the ASIC number and the interface that is configured in separate columns.

Usage Guidelines

The keywords and arguments that are available with the show spanning-tree command vary depending on the platform you are using and the network modules that are installed and operational.

The port-channel number values from 257 to 282 are supported on the Content Switching Module (CSM) and the Firewal Services Module (FWSM) only.

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.

When checking spanning tree-active states and you have a large number of VLANs, you can enter the show spanning-tree summary total command. You can display the total number of VLANs without having to scroll through the list of VLANs.

The valid values for keyword pathcoast method are:

• append : Appends the redirected output to a URL (supporting the append operation).

• begin : Begins with the matching line.

• exclude : Excludes matching lines.

• include : Includes matching lines.

• redirect : Redirects output to a URL.

• tee : Copies output to a URL.

When you run the show spanning-tree command for a VLAN or an interface the switch router will display the different port states for the VLAN or interface. The valid spanning-tree port states are listening, learning, forwarding, blocking, disabled, and loopback.

Device# 
show spanning-tree
VLAN0001
  Spanning tree enabled protocol rstp
  Root ID    Priority    32769
             Address     5c71.0dfe.8380
             This bridge is the root
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec

  Bridge ID  Priority    32769  (priority 32768 sys-id-ext 1)
             Address     5c71.0dfe.8380
             Hello Time   2 sec  Max Age 20 sec  Forward Delay 15 sec
             Aging Time  300 sec

Interface           Role Sts Cost      Prio.Nbr Type
------------------- ---- --- --------- -------- --------------------------------
Gi1/0/1             Desg FWD 20000     128.1    P2p
Gi1/0/18            Desg FWD 20000     128.18   P2p
Gi1/0/21            Desg FWD 20000     128.21   P2p
Te1/0/25            Desg FWD 20000     128.25   P2p
Te1/0/37            Desg FWD 2000      128.37   P2p
Te1/0/38            Desg FWD 2000      128.38   P2p
Te1/0/45            Desg FWD 20000     128.45   P2p
Te1/0/48            Desg FWD 20000     128.48   P2p

See the table below for definitions of the port states:

Usage Guidelines

The valid values for the interface argument 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.

The number of valid values for port-channel number are a maximum of 64 values ranging from 1 to 282. The port-channel number values from 257 to 282 are supported on the Content Switching Module (CSM) and the Firewall Services Module (FWSM) only.

The number of valid values for vlan are from 1 to 4094.

In the output display of the show spanning-tree mst configuration command, a warning message may be displayed. This message appears if you do not map secondary VLANs to the same instance as the associated primary VLAN. The display includes a list of 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

In the output display of the show spanning-tree mst configuration digest command, if the output applies to both standard and prestandard bridges at the same time on a per-port basis, two different digests are displayed.

If you configure a port to transmit prestandard PortFast bridge protocol data units (BPDUs) only, the prestandard flag displays in the show spanning-tree commands. The variations of the prestandard flag are as follows:

• Pre-STD (or pre-standard in long format): This flag is displayed 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 is displayed 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 prestandard (rcvd) in long format): This flag is displayed 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 Cisco recommends that you change the port configuration so that the interaction with the prestandard neighbor does not rely only on the autodetection mechanism.

If the configuration is not prestandard compliant (for example, a single MST instance has an ID that is greater than or equal to 16,) the prestandard digest is not computed and the following output is displayed:

Device# show spanning-tree mst configuration digest 

Name      [region1]
Revision  2     Instances configured 3
Digest          0x3C60DBF24B03EBF09C5922F456D18A03
Pre-std Digest  N/A, configuration not pre-standard compatible

MST BPDUs include an MSTCI that consists of the region name, region revision, and an MD5 digest of the VLAN-to-instance mapping of the MST configuration.

See the show spanning-tree mst command field description table for output descriptions.