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Contents
- Managing Switch Stacks
- Finding Feature Information
- Prerequisites for Switch Stacks
- Restrictions for Switch Stacks
- Information About Switch Stacks
- Switch Stack Overview
- Supported Features in a Switch Stack
- Switch Stack Membership
- Stack Member Numbers
- Stack Member Priority Values
- Switch Stack Bridge ID
- Persistent MAC Address on the Switch Stack
- Active Switch Election and Re-Election
- Switch Stack Configuration Files
- Offline Configuration to Provision a Stack Member
- Effects of Adding a Provisioned Switch to a Switch Stack
- Effects of Replacing a Provisioned Switch in a Switch Stack
- Effects of Removing a Provisioned Switch from a Switch Stack
- Stack Protocol Version
- Major Stack Protocol Version Number Incompatibility Among Stack-Capable Switches
- Minor Stack Protocol Version Number Incompatibility Among Stack-Capable Switches
- SDM Template Mismatch in Switch Stacks
- Switch Stack Management Connectivity
- Connectivity to Specific Stack Members
- Connectivity to the Switch Stack Through an IP Address
- Connectivity to the Switch Stack Through an SSH Session
- Connectivity to the Switch Stack Through Console Ports or Ethernet Management Ports
- Switch Stack Upgrade
- Auto-Upgrade
- Auto-Advise
- Examples of Auto-Advise Messages
- How to Configure a Switch Stack
- Enabling Persistent MAC Address
- Assigning a Stack Member Number
- Setting the Stack Member Priority Value
- Removing Provisioned Switch Information
- Displaying Incompatible Switches in the Switch Stack
- Upgrading an Incompatible Switch in the Switch Stack
- Troubleshooting the Switch Stack
- Accessing the CLI of a Specific Member
- Temporarily Disabling a Stack Port
- Re-Enabling a Stack Port While Another Member Starts
- Monitoring the Switch Stack
- Configuration Examples for Switch Stacks
- Switch Stack Configuration Scenarios
- Enabling Persistent MAC Address: Example
- Provisioning a New Member for a Switch Stack: Example
- show switch stack-ports summary Output: Example
- Software Loopback: Examples
- Software Loopback With No Connected Stack Cable: Example
- Software Loopback With Connected Stack Cables: Examples
- Finding a Disconnected Stack Cable: Example
- Fixing a Bad Connection Between Stack Ports: Example
- Additional References for Switch Stacks
- Feature Information for Switch Stack Features
Managing Switch Stacks
Finding Feature Information
Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release.
Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.
Related References
Information About Switch Stacks
- Switch Stack Overview
- Switch Stack Membership
- Stack Member Numbers
- Stack Member Priority Values
- Switch Stack Bridge ID
- Active Switch Election and Re-Election
- Switch Stack Configuration Files
- Offline Configuration to Provision a Stack Member
- Stack Protocol Version
- SDM Template Mismatch in Switch Stacks
- Switch Stack Management Connectivity
- Switch Stack Upgrade
Switch Stack Overview
The active switch controls the operation of the switch stack, and is the single point of stack-wide management. From the active switch, you configure:
- System-level (global) features that apply to all stack members
- Interface-level features for each stack member
The active switch contains the saved and running configuration files for the switch stack. The configuration files include the system-level settings for the switch stack and the interface-level settings for each stack member. Each stack member has a current copy of these files for back-up purposes.
Supported Features in a Switch Stack
The system-level features supported on the active switch are supported on the entire switch stack. If a switch in the stack is running the IP Base or IP Services licence level and the cryptographic (that is, supporting encryption) universal software image, we recommend that this switch be the active switch. Encryption features are unavailable if the active switch is running the IP Base or IP Services licence level and the noncryptographic software image.
Switch Stack Membership
A standalone switch is a switch stack with one stack member that also operates as the active switch. You can connect one standalone switch to another to create a switch stack containing two stack members, with one of them as the active switch. You can connect standalone switches to an existing switch stack to increase the stack membership.
If you replace a stack member with an identical model, the new switch functions with exactly the same configuration as the replaced switch, assuming that the new switch (referred to as the provisioned switch) is using the same member number as the replaced switch.
The operation of the switch stack continues uninterrupted during membership changes unless you remove the active switch or you add powered-on standalone switches or switch stacks.
- Adding powered-on switches (merging) causes all switches to reload and elect a new active switch from among themselves. The newly elected active switch retains its role and configuration. All other switches change their stack member numbers to the lowest available numbers and use the stack configuration of the newly elected active switch.
- Removing powered-on stack members causes the switch stack to divide (partition) into two or more switch stacks, each with the same configuration. This can cause an IP address configuration conflict in your network. If you want the switch stacks to remain separate, change the IP address or addresses of the newly created switch stacks.
If a newly created switch stack does not have an active switch or standby switch, the switch stack will reload and elect a new active switch.
Note
Make sure that you power off the switches that you add to or remove from the switch stack.
After adding or removing stack members, make sure that the switch stack is operating at full bandwidth . Press the Mode button on a stack member until the Stack mode LED is on. The last two right port LEDs on all switches in the stack should be green. Depending on the switch model, the last two right ports are 10-Gigabit Ethernet ports or small form-factor pluggable (SFP) module ports (10/100/1000 ports). If one or both of these LEDs are not green on any of the switches, the stack is not operating at full bandwidth.
If you did not intend to partition the switch stack:
For cabling and power considerations that affect creating switch stacks, see the switch hardware installation guide.
Stack Member Numbers
A new, out-of-the-box switch (one that has not joined a switch stack or has not been manually assigned a stack member number) ships with a default stack member number of 1. When it joins a switch stack, its default stack member number changes to the lowest available member number in the stack.
Stack members in the same switch stack cannot have the same stack member number. Every stack member, including a standalone switch, retains its member number until you manually change the number or unless the number is already being used by another member in the stack.
- If you manually change the stack member number by using the switch current-stack-member-number renumber new-stack-member-number EXEC command, the new number goes into effect after that stack member resets (or after you use the reload slot stack-member-number privileged EXEC command) and only if that number is not already assigned to any other members in the stack. Another way to change the stack member number is by changing the SWITCH_NUMBER environment variable. If the number is being used by another member in the stack, the switch selects the lowest available number in the stack. If you manually change the number of a stack member and no interface-level configuration is associated with that new member number, that stack member resets to its default configuration. You cannot use the switch current-stack-member-number renumber new-stack-member-number EXEC command on a provisioned switch. If you do, the command is rejected.
- If you move a stack member to a different switch stack, the stack member retains its number only if the number is not being used by another member in the stack. If it is being used, the switch selects the lowest available number in the stack.
- If you merge switch stacks, the switches that join the switch stack of a new active switch select the lowest available numbers in the stack.
As described in the hardware installation guide, you can use the switch port LEDs in Stack mode to visually determine the stack member number of each stack member.
Stack Member Priority Values
A higher priority value for a stack member increases its likelihood of being elected active switch and retaining its stack member number. The priority value can be 1 to 15. The default priority value is 1. You can display the stack member priority value by using the show switch EXEC command.
Note
We recommend assigning the highest priority value to the switch that you prefer to be the active switch. This ensures that the switch is re-elected as active switch if a re-election occurs.
To change the priority value for a stack member, use the switch stack-member-number priority new priority-value EXEC command. Another way to change the member priority value is by changing the SWITCH_PRIORITY environment variable.
The new priority value takes effect immediately but does not affect the current active switch. The new priority value helps determine which stack member is elected as the new active switch when the current active switch or the switch stack resets.
Switch Stack Bridge ID
A switch stack is identified in the network by its bridge ID, which is determined by the MAC address of the stack master.
If the stack master changes, the MAC address of the new active switch determines the new bridge ID.
If the entire switch stack reloads ,the switch stack uses the MAC address of the active switch.
Persistent MAC Address on the Switch Stack
The switch stack MAC address is determined by the MAC address of the stack master. When a stack master is removed from the stack and a new stack master takes over, the default is for the MAC address of the new stack master to immediately become the new stack MAC address.
However, you can use the persistent MAC address feature to set a time delay before the stack MAC address changes. During this time period, if the previous stack master rejoins the stack, the stack continues to use that MAC address as the stack MAC address, even if the switch is now a stack member and not a stack master. If the previous stack master does not rejoin the stack during this period, the switch stack takes the MAC address of the new stack master as the stack MAC address.
You can also configure stack MAC persistency so that the stack MAC address never changes to the new master MAC address.
Note
If the entire switch stack reloads, it uses the MAC address of the stack master as the stack MAC address.
Active Switch Election and Re-Election
All stack members are eligible to be the active switch or the standby switch. If the active switch becomes unavailable, the standby switch becomes the active switch.
An active switch retains its role unless one of these events occurs:
The active switch is elected or re-elected based on one of these factors and in the order listed:
- The switch that is currently the active switch.
- The switch with the highest stack member priority value.
Note
We recommend assigning the highest priority value to the switch that you prefer to be the active switch. This ensures that the switch is re-elected as active switch if a re-election occurs.
- The switch with the shortest start-up time. Differences in start-up times between the feature image licenses determine the active switch. For example, a switch running the IP Services license level has a higher priority than the switch running the IP Base license level, but the switch running the IP Base license level becomes the active switch because the other switch takes 10 seconds longer to start. To avoid this problem, upgrade the switch running the IP Base license level to the same licensed feature set and software image as the other switch, or manually start the active switch and wait at least 8 seconds before starting the new member switch that is running the IP Base license level.
- The switch with the lowest MAC address.
After election, the new active switch becomes available after a few seconds. In the meantime, the switch stack uses the forwarding tables in memory to minimize network disruption. The physical interfaces on the other available stack members are not affected during a new active switch election and reset.
When the previous active switch becomes available, it does not resume its role as the active switch.
If you power on or reset an entire switch stack, some stack members might not participate in the active switch election. Stack members that are powered on within the same 2-minute timeframe participate in the active switch election and have a chance to become the active switch. Stack members that are powered on after the 20-second timeframe do not participate in this initial election and become stack members. For powering considerations that affect active-switch elections, see the switch hardware installation guide.
As described in the hardware installation guide, you can use the ACTV LED on the switch to see if the switch is the active switch.
Switch Stack Configuration Files
The active switch has the saved and running configuration files for the switch stack. All stack members periodically receive synchronized copies of the configuration files from the active switch. If the active switch becomes unavailable, any stack member assuming the role of active switch has the latest configuration files.
The configuration files record these settings:
- System-level (global) configuration settings—such as IP, STP, VLAN, and SNMP settings—that apply to all stack members
- Stack member interface-specific configuration settings that are specific for each stack member
Note
The interface-specific settings of the active switch are saved if the active switch is replaced without saving the running configuration to the startup configuration.
A new, out-of-box switch joining a switch stack uses the system-level settings of that switch stack. If a switch is moved to a different switch stack, that switch loses its saved configuration file and uses the system-level configuration of the new switch stack.
The interface-specific configuration of each stack member is associated with the stack member number. Stack members retain their numbers unless they are manually changed or they are already used by another member in the same switch stack.
- If an interface-specific configuration does not exist for that member number, the stack member uses its default interface-specific configuration.
- If an interface-specific configuration exists for that member number, the stack member uses the interface-specific configuration associated with that member number.
If you replace a failed member with an identical model, the replacement member automatically uses the same interface-specific configuration as the failed switch. You do not need to reconfigure the interface settings. The replacement switch (referred to as the provisioned switch) must have the same stack member number as the failed switch.
You back up and restore the stack configuration in the same way as you would for a standalone switch configuration.
Offline Configuration to Provision a Stack Member
You can use the offline configuration feature to provision (to supply a configuration to) a new switch before it joins the switch stack. You can configure the stack member number, the switch type, and the interfaces associated with a switch that is not currently part of the stack. The configuration that you create on the switch stack is called the provisioned configuration. The switch that is added to the switch stack and that receives this configuration is called the provisioned switch.
You manually create the provisioned configuration through the switch stack-member-number provision type global configuration command. The provisioned configuration is automatically created when a switch is added to a switch stack and when no provisioned configuration exists. When you configure the interfaces associated with a provisioned switch (for example, as part of a VLAN), the switch stack accepts the configuration, and the information appears in the running configuration. The interface associated with the provisioned switch is not active, operates as if it is administratively shut down, and the no shutdown interface configuration command does not return it to active service. The interface associated with the provisioned switch does not appear in the display of the specific feature; for example, it does not appear in the show vlan user EXEC command output.
The switch stack retains the provisioned configuration in the running configuration whether or not the provisioned switch is part of the stack. You can save the provisioned configuration to the startup configuration file by entering the copy running-config startup-config privileged EXEC command. The startup configuration file ensures that the switch stack can reload and can use the saved information whether or not the provisioned switch is part of the switch stack.
- Effects of Adding a Provisioned Switch to a Switch Stack
- Effects of Replacing a Provisioned Switch in a Switch Stack
- Effects of Removing a Provisioned Switch from a Switch Stack
Effects of Adding a Provisioned Switch to a Switch Stack
When you add a provisioned switch to the switch stack, the stack applies either the provisioned configuration or the default configuration. This table lists the events that occur when the switch stack compares the provisioned configuration with the provisioned switch.
Table 1 Results of Comparing the Provisioned Configuration with the Provisioned Switch Scenario
Result
The stack member numbers and the switch types match.
The switch stack applies the provisioned configuration to the provisioned switch and adds it to the stack.
The stack member numbers match but the switch types do not match.
The switch stack applies the default configuration to the provisioned switch and adds it to the stack.
The provisioned configuration is changed to reflect the new information.
The stack member number is not found in the provisioned configuration.
The switch stack applies the default configuration to the provisioned switch and adds it to the stack.
The provisioned configuration is changed to reflect the new information.
The stack member number of the provisioned switch is in conflict with an existing stack member.
The active switch assigns a new stack member number to the provisioned switch.
The stack member numbers and the switch types match:
The switch stack applies the provisioned configuration to the provisioned switch and adds it to the stack.
The provisioned configuration is changed to reflect the new information.
The stack member numbers match, but the switch types do not match:
The switch stack applies the default configuration to the provisioned switch and adds it to the stack.
The provisioned configuration is changed to reflect the new information.
The stack member number of the provisioned switch is not found in the provisioned configuration.
The switch stack applies the default configuration to the provisioned switch and adds it to the stack.
If you add a provisioned switch that is a different type than specified in the provisioned configuration to a powered-down switch stack and then apply power, the switch stack rejects the (now incorrect) switch stack-member-number provision type global configuration command in the startup configuration file. However, during stack initialization, the nondefault interface configuration information in the startup configuration file for the provisioned interfaces (potentially of the wrong type) is executed. Depending on the differences between the actual switch type and the previously provisioned switch type, some commands are rejected, and some commands are accepted.
Note
If the switch stack does not contain a provisioned configuration for a new switch, the switch joins the stack with the default interface configuration. The switch stack then adds to its running configuration with a switch stack-member-number provision type global configuration command that matches the new switch.
Effects of Replacing a Provisioned Switch in a Switch Stack
When a provisioned switch in a switch stack fails, is removed from the stack, and is replaced with another switch, the stack applies either the provisioned configuration or the default configuration to it. The events that occur when the switch stack compares the provisioned configuration with the provisioned switch are the same as those when you add a provisioned switch to a stack.
Effects of Removing a Provisioned Switch from a Switch Stack
If you remove a provisioned switch from the switch stack, the configuration associated with the removed stack member remains in the running configuration as provisioned information. To completely remove the configuration, use the no switch stack-member-number provision global configuration command.
Stack Protocol Version
Each software image includes a stack protocol version. The stack protocol version has a major version number and a minor version number (for example 1.4, where 1 is the major version number and 4 is the minor version number). Both version numbers determine the level of compatibility among the stack members.
Switches with the same Cisco IOS software version have the same stack protocol version. Such switches are fully compatible, and all features function properly across the switch stack. A switch with the same Cisco IOS software version as the active switch can immediately join the switch stack.
If an incompatibility exists, the fully functional stack members generate a system message that describes the cause of the incompatibility on the specific stack members. The active switch sends the message to all stack members.
- Major Stack Protocol Version Number Incompatibility Among Stack-Capable Switches
- Minor Stack Protocol Version Number Incompatibility Among Stack-Capable Switches
Major Stack Protocol Version Number Incompatibility Among Stack-Capable Switches
Switches with different major Cisco IOS software versions usually have different stack protocol versions. Switches with different major version numbers are incompatible and cannot exist in the same switch stack.
Minor Stack Protocol Version Number Incompatibility Among Stack-Capable Switches
Switches with the same major version number but with a different minor version number are considered partially compatible. When connected to a switch stack, a partially compatible switch enters version-mismatch (VM) mode and cannot join the stack as a fully functioning member. The software detects the mismatched software and tries to upgrade (or downgrade) the switch in VM mode with the switch stack image or with a tar file image from the switch stack flash memory. The software uses the automatic upgrade (auto-upgrade) and the automatic advise (auto-advise) features.
SDM Template Mismatch in Switch Stacks
All stack members use the Switch Database Management (SDM) template configured on the active switch.
Version-mismatch (VM) mode has priority over SDM-mismatch mode. If a VM-mode condition and an SDM-mismatch mode exist, the switch stack first attempts to resolve the VM-mode condition.
You can use the show switch privileged EXEC command to see if any stack members are in SDM-mismatch mode.
Switch Stack Management Connectivity
You manage the switch stack and the stack member interfaces through the active switch. You can use the CLI, SNMP, and supported network management applications such as CiscoWorks. You cannot manage stack members on an individual switch basis.
Note
Use SNMP to manage network features across the stack that are defined by supported MIBs. The switch does not support MIBs to manage stacking-specific features such as stack membership and election.
- Connectivity to Specific Stack Members
- Connectivity to the Switch Stack Through an IP Address
- Connectivity to the Switch Stack Through an SSH Session
- Connectivity to the Switch Stack Through Console Ports or Ethernet Management Ports
Connectivity to Specific Stack Members
If you want to configure a specific stack member port, you must include the stack member number in the CLI command interface notation.
Connectivity to the Switch Stack Through an IP Address
The switch stack is managed through a single IP address. The IP address is a system-level setting and is not specific to the active switch or to any other stack member. You can still manage the stack through the same IP address even if you remove the active switch or any other stack member from the stack, provided there is IP connectivity.
Note
Stack members retain their IP addresses when you remove them from a switch stack. To avoid a conflict by having two devices with the same IP address in your network, change the IP addresses of any switches that you remove from the switch stack.
Connectivity to the Switch Stack Through an SSH Session
In a mixed stack, Secure Shell (SSH) connectivity to the switch stack can be lost if an active switch running the cryptographic software image and the IP Base or IP Services license level fails and is replaced by a switch that is running the noncryptographic image and the same license level. We recommend that a switch running the cryptographic software image and the IP Base or IP Services license level be the an active switch. Encryption features are unavailable if the an active switch is running the noncryptographic software image.
Connectivity to the Switch Stack Through Console Ports or Ethernet Management Ports
You can connect to the active switch by using one of these methods:
- You can connect a terminal or a PC to the active switch through the console port of one or more stack members.
- You can connect a PC to the active switch through the Ethernet management ports of one or more stack members.
Be careful when using multiple CLI sessions to the active switch. Commands that you enter in one session are not displayed in the other sessions. Therefore, it is possible that you might not be able to identify the session from which you entered a command.
We recommend using only one CLI session when managing the switch stack.
Switch Stack Upgrade
Before you start the process, configure a redundant uplink to the network to ensure that the stack has network connectivity. You can also set the stack boot time.
When upgrading the whole switch stack, or a subset of switches in the stack, the active switch communicates with each stack member to coordinate the upgrade. When the upgrade completes, all switches in the stack reload to complete the installation.
The active switch copies the source bundle to each member in the stack. Each stack member then performs various installation steps. If any step fails on a stack member, the active switch instructs all stack members to abort the installation.
If the active switch becomes unavailable during the installation, all stack members abort the installation.
Auto-Upgrade
The purpose of the auto-upgrade feature is to allow a switch to be upgraded to a compatible software image, so that the switch can join the switch stack.
When a new switch attempts to join a switch stack, each stack member performs compatibility checks with itself and the new switch. Each stack member sends the results of the compatibility checks to the active switch, which uses the results to determine whether the switch can join the switch stack. If the software on the new switch is incompatible with the switch stack, the new switch enters version-mismatch (VM) mode.
If the auto-upgrade feature is enabled on the new switch, the active switch automatically upgrades the new switch with the same software image running on a compatible stack member. Auto-upgrade starts a few minutes after the mismatched software is detected before starting.
Auto-upgrade is disabled, by default.
Auto-upgrade includes an auto-copy process and an auto-extract process.
- Auto-copy automatically copies the software image running on any stack member to the new switch to automatically upgrade it. Auto-copy occurs if auto-upgrade is enabled, if there is enough flash memory in the new switch, and if the software image running on the switch stack is suitable for the new switch.
Note
A switch in VM mode might not run all released software. For example, new switch hardware is not recognized in earlier versions of software.- Automatic extraction (auto-extract) occurs when the auto-upgrade process cannot find the appropriate software in the stack to copy to the new switch. In that case, the auto-extract process searches all switches in the stack for the tar file needed to upgrade the switch stack or the new switch. The tar file can be in any flash file system in the switch stack or in the new switch. If a tar file suitable for the new switch is found on a stack member, the process extracts the file and automatically upgrades the new switch.
The auto-upgrade feature is not available in bundle mode. The switch stack must be running in installed mode. If the switch stack is in bundle mode, use the software expand privileged EXEC command to change to installed mode.
You can enable auto-upgrade by using the software auto-upgrade enable global configuration command on the new switch. You can check the status of auto-upgrade by using the show boot privileged EXEC command and by checking the Auto upgrade line in the display.
You can configure auto-upgrade to upgrade the new switch with a specific software bundle by using the software auto-upgrade source url global configuration command. If the software bundle is invalid, the new switch is upgraded with the same software image running on a compatible stack member.
When the auto-upgrade process is complete, the new switch reloads and joins the stack as a fully functioning member. If you have both cables connected during the reload, network downtime does not occur because the switch stack operates on two rings.
Note
Auto-upgrade performs the upgrade only when the two feature sets are the same type.Auto-Advise
The auto-advise feature is triggered when:
- The auto-upgrade feature is disabled.
- The new switch is in bundle mode and the stack is in installed mode. Auto-advise displays syslog messages about using the software auto-upgrade privileged EXEC command to change the new switch to installed mode.
- The stack is in bundle mode. Auto-advise displays syslog messages about booting the new switch in bundle mode so that it can join the stack.
- An auto-upgrade attempt fails because the new switch is running incompatible software. After the switch stack performs compatibility checks with the new switch, auto-advise displays syslog messages about whether the new switch can be auto-upgraded.
Examples of Auto-Advise Messages
Auto-Upgrade Is Disabled and Incompatible Switch Attempting to Join: Example
This sample auto-advise output shows the system messages displayed when the auto-upgrade feature is disabled and an incompatible switch 1 tries to join the switch stack:
*Oct 18 08:36:19.379: %INSTALLER-6-AUTO_ADVISE_SW_INITIATED: 2 installer: Auto advise initiated for switch 1 *Oct 18 08:36:19.380: %INSTALLER-6-AUTO_ADVISE_SW: 2 installer: Searching stack for software to upgrade switch 1 *Oct 18 08:36:19.382: %INSTALLER-6-AUTO_ADVISE_SW: 2 installer: Switch 1 with incompatible software has been *Oct 18 08:36:19.382: %INSTALLER-6-AUTO_ADVISE_SW: 2 installer: added to the stack. The software running on *Oct 18 08:36:19.382: %INSTALLER-6-AUTO_ADVISE_SW: 2 installer: all stack members was scanned and it has been *Oct 18 08:36:19.382: %INSTALLER-6-AUTO_ADVISE_SW: 2 installer: determined that the 'software auto-upgrade' *Oct 18 08:36:19.382: %INSTALLER-6-AUTO_ADVISE_SW: 2 installer: command can be used to install compatible *Oct 18 08:36:19.382: %INSTALLER-6-AUTO_ADVISE_SW: 2 installer: software on switch 1.Auto-Upgrade is Disabled and New Switch is in Bundle Mode: Example
This sample auto-advise output shows the system messages displayed when auto-upgrade is disabled and a switch running in bundle mode tries to join the stack that's running in installed mode:
*Oct 18 11:09:47.005: %INSTALLER-6-AUTO_ADVISE_SW_INITIATED: 2 installer: Auto advise initiated for switch 1 *Oct 18 11:09:47.005: %INSTALLER-6-AUTO_ADVISE_SW: 2 installer: Switch 1 running bundled software has been added *Oct 18 11:09:47.005: %INSTALLER-6-AUTO_ADVISE_SW: 2 installer: to the stack that is running installed software. *Oct 18 11:09:47.005: %INSTALLER-6-AUTO_ADVISE_SW: 2 installer: The 'software auto-upgrade' command can be used to *Oct 18 11:09:47.005: %INSTALLER-6-AUTO_ADVISE_SW: 2 installer: convert switch 1 to the installed running mode by *Oct 18 11:09:47.005: %INSTALLER-6-AUTO_ADVISE_SW: 2 installer: installing its running software.How to Configure a Switch Stack
- Enabling Persistent MAC Address
- Assigning a Stack Member Number
- Setting the Stack Member Priority Value
- Removing Provisioned Switch Information
- Displaying Incompatible Switches in the Switch Stack
- Upgrading an Incompatible Switch in the Switch Stack
Enabling Persistent MAC Address
SUMMARY STEPSThis procedure is optional.
When you enter the command to configure this feature, a warning message appears containing the consequences of your configuration. You should use this feature cautiously. Using the old active switch MAC address elsewhere in the same domain could result in lost traffic.
1. configure terminal
2. stack-mac persistent timer [0 | time-value]
3. end
4. copy running-config startup-config
DETAILED STEPSAssigning a Stack Member Number
SUMMARY STEPS
1. switch current-stack-member-number renumber new-stack-member-number
2. reload slot stack-member-number
3. copy running-config startup-config
DETAILED STEPS
Command or Action Purpose
Step 1 switch current-stack-member-number renumber new-stack-member-number
Example:Switch# switch 3 renumber 5You can display the current stack member number by using the show switch user EXEC command.
Step 2 reload slot stack-member-number
Example:Switch# reload slot 5Resets the stack member.
Step 3 copy running-config startup-config
Example:Switch# copy running-config startup-configSaves your entries in the configuration file.
Setting the Stack Member Priority Value
SUMMARY STEPS
1. switch stack-member-number priority new-priority-number
2. reload slot stack-member-number
3. copy running-config startup-config
DETAILED STEPS
Command or Action Purpose
Step 1 switch stack-member-number priority new-priority-number
Example:Switch# switch 3 priority 2You can display the current priority value by using the show switch user EXEC command.
The new priority value takes effect immediately but does not affect the current active switch. The new priority value helps determine which stack member is elected as the new active switch when the current active switch or switch stack resets.
Step 2 reload slot stack-member-number
Example:Switch# reload slot 3Resets the stack member, and applies this configuration change.
Step 3 copy running-config startup-config
Example:Switch# copy running-config startup-config(Optional) Saves your entries in the configuration file.
Removing Provisioned Switch Information
SUMMARY STEPS
1. Remove the provisioned switch from the stack.
2. no switch stack-member-number provision
3. copy running-config startup-config
DETAILED STEPS
Command or Action Purpose
Step 1 Remove the provisioned switch from the stack. Step 2 no switch stack-member-number provision
Example:Switch(config)# no switch 3 provisionRemoves the provisioning information for the specified member.
Step 3 copy running-config startup-config
Example:Switch# copy running-config startup-config(Optional) Saves your entries in the configuration file.
If you are removing a provisioned switch in a stack with this configuration:
- The stack has four members
- Stack member 1 is the active switch
- Stack member 3 is a provisioned switch
and want to remove the provisioned information and to avoid receiving an error message, you can remove power from stack member 3, disconnect the cables between the stack member 3 and switches to which it is connected, reconnect the cables between the remaining stack members, and enter the no switch stack-member-number provision global configuration command.
Upgrading an Incompatible Switch in the Switch Stack
SUMMARY STEPS
1. software auto-upgrade
2. copy running-config startup-config
DETAILED STEPS
Command or Action Purpose
Step 1 software auto-upgrade
Example:Switch# software auto-upgradeUpgrades incompatible switches in the switch stack, or changes switches in bundle mode to installed mode.
Step 2 copy running-config startup-config
Example:Switch# copy running-config startup-config(Optional) Saves your entries in the configuration file.
Troubleshooting the Switch Stack
Accessing the CLI of a Specific Member
SUMMARY STEPS
1. session switch stack-member-number
2. exit
DETAILED STEPS
Command or Action Purpose Temporarily Disabling a Stack Port
SUMMARY STEPSWhen a stack port is flapping and causing instability in the stack, be careful when using the switch stack-member-number stack port port-number disable privileged EXEC command. When you disable the stack port, the stack operates at half bandwidth.
A stack is in the full-ring state when all members are connected through the stack ports and are in the ready state.
The stack is in the partial-ring state when
1. switch stack-member-number stack port port-number disable
2. switch stack-member-number stack port port-number enable
3. copy running-config startup-config
DETAILED STEPS
Command or Action Purpose
Step 1 switch stack-member-number stack port port-number disable
Example:Switch# switch 2 stack port 1 disableDisables the specified stack port.
Step 2 switch stack-member-number stack port port-number enable
Example:Switch# switch 2 stack port 1 enableRe-enables the stack port after the problem is resolved.
Step 3 copy running-config startup-config
Example:Switch# copy running-config startup-config(Optional) Saves your entries in the configuration file.
When you disable a stack port and the stack is in the full-ring state, you can disable only one stack port. This message appears:
Enabling/disabling a stack port may cause undesired stack changes. Continue?[confirm]When you disable a stack port and the stack is in the partial-ring state, you cannot disable the port. This message appears:
Disabling stack port not allowed with current stack configuration.Re-Enabling a Stack Port While Another Member Starts
SUMMARY STEPSStack Port 1 on Switch 1 is connected to Port 2 on Switch 4. If Port 1 is flapping, you can disable Port 1 with the switch 1 stack port 1 disable privileged EXEC command. While Port 1 on Switch 1 is disabled and Switch 1 is still powered on:
1. Disconnect the stack cable between Port 1 on Switch 1 and Port 2 on Switch 4.
2. Remove Switch 4 from the stack.
3. Add a switch to replace Switch 4 and assign it switch-number 4.
4. Reconnect the cable between Port 1 on Switch 1 and Port 2 on Switch 4 (the replacement switch).
5. Re-enable the link between the switches. Enter the switch 1 stack port 1 enable privileged EXEC command to enable Port 1 on Switch 1.
6. Power on Switch 4
DETAILED STEPS
Step 1 Disconnect the stack cable between Port 1 on Switch 1 and Port 2 on Switch 4. Step 2 Remove Switch 4 from the stack. Step 3 Add a switch to replace Switch 4 and assign it switch-number 4. Step 4 Reconnect the cable between Port 1 on Switch 1 and Port 2 on Switch 4 (the replacement switch). Step 5 Re-enable the link between the switches. Enter the switch 1 stack port 1 enable privileged EXEC command to enable Port 1 on Switch 1. Step 6 Power on Switch 4
Powering on Switch 4 before enabling the Port 1 on Switch 1 might cause one of the switches to reload.
If Switch 4 is powered on first, you might need to enter the switch 1 stack port 1 enable and the switch 4 stack port 2 enable privileged EXEC commands to bring up the link.
Monitoring the Switch Stack
Table 2 Commands for Displaying Stack Information Command
Description
show switch
Displays summary information about the stack, including the status of provisioned switches and switches in version-mismatch mode.
show switch stack-member-number
Displays information about a specific member.
show switch detail
Displays detailed information about the stack.
show switch neighbors
Displays the stack neighbors.
show switch stack-ports [summary]
Displays port information for the stack. Use the summary keyword to display the stack cable length, the stack link status, and the loopback status.
Configuration Examples for Switch Stacks
- Switch Stack Configuration Scenarios
- Enabling Persistent MAC Address: Example
- Provisioning a New Member for a Switch Stack: Example
- show switch stack-ports summary Output: Example
- Software Loopback: Examples
- Software Loopback With No Connected Stack Cable: Example
- Software Loopback With Connected Stack Cables: Examples
- Finding a Disconnected Stack Cable: Example
- Fixing a Bad Connection Between Stack Ports: Example
Switch Stack Configuration Scenarios
Most of these switch stack configuration scenarios assume that at least two switches are connected through their ports.
Table 3 Configuration ScenariosScenario
Result
Active switch election specifically determined by existing active switches
Connect two powered-on switch stacks through the ports.
Only one of the two active switches becomes the new active switch. None of the other stack members become the active switch.
Active switch election specifically determined by the stack member priority value
The stack member with the higher priority value is elected active switch.
Active switch election specifically determined by the MAC address
Assuming that both stack members have the same priority value, configuration file, and license level, restart both stack members at the same time.
The stack member with the lower MAC address is elected active switch.
Stack member number conflict
Assuming that one stack member has a higher priority value than the other stack member:
The stack member with the higher priority value retains its stack member number. The other stack member has a new stack member number.
Add a stack member
The active switch is retained. The new switch is added to the switch stack.
Active switch failure
Remove (or power off) the active switch.
One of the remaining stack members becomes the new stack master. All other stack members in the stack remain as stack members and do not reboot.
Add more than stack members
Two switches become active switches. One active switch has stack members. The other active switch remains as a standalone switch.
Use the Mode button and port LEDs on the switches to identify which switches are active switches and which switches belong to each active switch.
Enabling Persistent MAC Address: Example
This example shows how to configure the persistent MAC address feature for a 7-minute time delay and to verify the configuration:
Switch(config)# stack-mac persistent timer 7 WARNING: The stack continues to use the base MAC of the old Master WARNING: as the stack MAC after a master switchover until the MAC WARNING: persistency timer expires. During this time the Network WARNING: Administrators must make sure that the old stack-mac does WARNING: not appear elsewhere in this network domain. If it does, WARNING: user traffic may be blackholed. Switch(config)# end Switch# show switch Switch/Stack Mac Address : 0016.4727.a900 Mac persistency wait time: 7 mins H/W Current Switch# Role Mac Address Priority Version State ---------------------------------------------------------- *1 Active 0016.4727.a900 1 P2B ReadyProvisioning a New Member for a Switch Stack: Example
This example shows how to provision a switch with a stack member number of 2 for the switch stack. The show running-config command output shows the interfaces associated with the provisioned switch:
Switch(config)# switch 2 provision switch_PID Switch(config)# end Switch# show running-config | include switch 2 ! interface GigabitEthernet2/0/1 ! interface GigabitEthernet2/0/2 ! interface GigabitEthernet2/0/3 <output truncated>show switch stack-ports summary Output: Example
Only Port 1 on stack member 2 is disabled.
Switch# show switch stack-ports summary Switch#/ Stack Neighbor Cable Link Link Sync # In Port# Port Length OK Active OK Changes Loopback Status To LinkOK -------- ------ -------- -------- ---- ------ ---- --------- -------- 1/1 OK 3 50 cm Yes Yes Yes 1 No 1/2 Down None 3 m Yes No Yes 1 No 2/1 Down None 3 m Yes No Yes 1 No 2/2 OK 3 50 cm Yes Yes Yes 1 No 3/1 OK 2 50 cm Yes Yes Yes 1 No 3/2 OK 1 50 cm Yes Yes Yes 1 No
Table 4 show switch stack-ports summary Command Output Field
Description
Switch#/Port#
Member number and its stack port number.
Stack Port Status
Status of the stack port.
Neighbor
Switch number of the active member at the other end of the stack cable.
Cable Length
Valid lengths are 50 cm, 1 m, or 3 m.
If the switch cannot detect the cable length, the value is no cable. The cable might not be connected, or the link might be unreliable.
Link OK
Whether the stack cable is connected and functional. There may or may not be a neighbor connected on the other end.
The link partner is a stack port on a neighbor switch.
Link Active
Whether a neighbor is connected on the other end of the stack cable.
Sync OK
Whether the link partner sends valid protocol messages to the stack port.
# Changes to LinkOK
The relative stability of the link.
If a large number of changes occur in a short period of time, link flapping can occur.
In Loopback
Whether a stack cable is attached to a stack port on the member.
Software Loopback: Examples
In a stack with three members, stack cables connect all the members.
Switch# show switch stack-ports summary Switch#/ Stack Neighbor Cable Link Link Sync # In Port# Port Length OK Active OK Changes Loopback Status To LinkOK -------- ------ -------- -------- ---- ------ ---- --------- -------- 1/1 OK 3 50 cm Yes Yes Yes 1 No 1/2 OK 2 3 m Yes Yes Yes 1 No 2/1 OK 1 3 m Yes Yes Yes 1 No 2/2 OK 3 50 cm Yes Yes Yes 1 No 3/1 OK 2 50 cm Yes Yes Yes 1 No 3/2 OK 1 50 cm Yes Yes Yes 1 NoIf you disconnect the stack cable from Port 1 on Switch 1, these messages appear:
01:09:55: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 2 Switch 3 has changed to state DOWN 01:09:56: %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 1 Switch 1 has changed to state DOWN Switch# show switch stack-ports summary Switch#/ Stack Neighbor Cable Link Link Sync # In Port# Port Length OK Active OK Changes Loopback Status To LinkOK -------- ------ -------- -------- ---- ------ ---- --------- -------- 1/1 Absent None No cable No No No 1 No 1/2 OK 2 3 m Yes Yes Yes 1 No 2/1 OK 1 3 m Yes Yes Yes 1 No 2/2 OK 3 50 cm Yes Yes Yes 1 No 3/1 OK 2 50 cm Yes Yes Yes 1 No 3/2 Down None 50 cm No No No 1 NoIf you disconnect the stack cable from Port 2 on Switch 1, the stack splits.
Switch 2 and Switch 3 are now in a two-member stack connected through stack cables.
Switch# show sw stack-ports summary Switch#/ Stack Neighbor Cable Link Link Sync # In Port# Port Length OK Active OK Changes Loopback Status To LinkOK -------- ------ -------- -------- ---- ------ ---- --------- -------- 2/1 Down None 3 m No No No 1 No 2/2 OK 3 50 cm Yes Yes Yes 1 No 3/1 OK 2 50 cm Yes Yes Yes 1 No 3/2 Down None 50 cm No No No 1 NoSwitch 1 is a standalone switch.
Switch# show switch stack-ports summary Switch#/ Stack Neighbor Cable Link Link Sync # In Port# Port Length OK Active OK Changes Loopback Status To LinkOK -------- ------ -------- -------- ---- ------ ---- --------- -------- 1/1 Absent None No cable No No No 1 Yes 1/2 Absent None No cable No No No 1 YesSoftware Loopback With No Connected Stack Cable: Example
Switch# show switch stack-ports summary Switch#/ Stack Neighbor Cable Link Link Sync # In Port# Port Length OK Active OK Changes Loopback Status To LinkOK -------- ------ -------- -------- ---- ------ ---- --------- -------- 1/1 Absent None No cable No No No 1 Yes 1/2 Absent None No cable No No No 1 YesSoftware Loopback With Connected Stack Cables: Examples
- On Port 1 on Switch 1, the port status is Down, and a cable is connected. On Port 2 on Switch 1, the port status is Absent, and no cable is connected.
Switch# show switch stack-ports summary Switch#/ Stack Neighbor Cable Link Link Sync # In Port# Port Length OK Active OK Changes Loopback Status To LinkOK -------- ------ -------- -------- ---- ------ ---- --------- -------- 1/1 Down None 50 Cm No No No 1 No 1/2 Absent None No cable No No No 1 No- In a physical loopback, a cable connects both stack ports on a switch. You can use this configuration to test
Switch# show switch stack-ports summary Switch#/ Stack Neighbor Cable Link Link Sync # In Port# Port Length OK Active OK Changes Loopback Status To LinkOK -------- ------ -------- -------- ---- ------ ---- --------- -------- 2/1 OK 2 50 cm Yes Yes Yes 1 No 2/2 OK 2 50 cm Yes Yes Yes 1 NoThe port status shows thatFinding a Disconnected Stack Cable: Example
Stack cables connect all stack members. Port 2 on Switch 1 connects to Port 1 on Switch 2.
This is the port status for the members:
Switch# show switch stack-ports summary Switch#/ Stack Neighbor Cable Link Link Sync # In Port# Port Length OK Active OK Changes Loopback Status To LinkOK -------- ------ -------- -------- ---- ------ ---- --------- -------- 1/1 OK 2 50 cm Yes Yes Yes 0 No 1/2 OK 2 50 cm Yes Yes Yes 0 No 2/1 OK 1 50 cm Yes Yes Yes 0 No 2/2 OK 1 50 cm Yes Yes Yes 0 NoIf you disconnect the cable from Port 2 on Switch 1, these messages appear:
%STACKMGR-4-STACK_LINK_CHANGE: Stack Port 1 Switch 2 has changed to state DOWN %STACKMGR-4-STACK_LINK_CHANGE: Stack Port 2 Switch 1 has changed to state DOWNThis is now the port status:
Switch# show switch stack-ports summary Switch#/ Stack Neighbor Cable Link Link Sync # In Port# Port Length OK Active OK Changes Loopback Status To LinkOK -------- ------ -------- -------- ---- ------ ---- --------- -------- 1/1 OK 2 50 cm Yes Yes Yes 1 No 1/2 Absent None No cable No No No 2 No 2/1 Down None 50 cm No No No 2 No 2/2 OK 1 50 cm Yes Yes Yes 1 NoOnly one end of the cable connects to a stack port, Port 1 on Switch 2.
- The Stack Port Status value for Port 2 on Switch 1 is Absent, and the value for Port 1 on Switch 2 is Down.
- The Cable Length value is No cable.
Diagnosing the problem:
Fixing a Bad Connection Between Stack Ports: Example
Stack cables connect all members. Port 2 on Switch 1 connects to Port 1 on Switch 2.
This is the port status:
Switch# show switch stack-ports summary Switch#/ Stack Neighbor Cable Link Link Sync # In Port# Port Length OK Active OK Changes Loopback Status To LinkOK -------- ------ -------- -------- ---- ------ ---- --------- -------- 1/1 OK 2 50 cm Yes Yes Yes 1 No 1/2 Down None 50 cm No No No 2 No 2/1 Down None 50 cm No No No 2 No 2/2 OK 1 50 cm Yes Yes Yes 1 NoDiagnosing the problem:
- The Stack Port Status value is Down.
- Link OK, Link Active, and Sync OK values are No.
- The Cable Length value is 50 cm. The switch detects and correctly identifies the cable.
The connection between Port 2 on Switch 1 and Port 1 on Switch 2 is unreliable on at least one of the connector pins.
Additional References for Switch Stacks
MIBs
Technical Assistance
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