Chapter 1. Managing Switch Stacks

A switch stack can have up to eight stacking-capable switches connected through their StackWise ports. The stack members work together as a unified system. Layer 2 and Layer 3 protocols present the entire switch stack as a single entity to the network.

- Prerequisites for Switch Stacks

- Restrictions for Switch Stacks

- Information About Switch Stacks

- How to Configure a Switch Stack

- Configuration Examples for Switch Stacks

- Feature History for Switch Stacks

Prerequisites for Switch Stacks

- All the switches in the stack must be running the same license level as the active switch. For information about license levels, see the System Management section of this guide.

- All the switches in the switch stack must be running compatible software versions.

Restrictions for Switch Stacks

The following are the restrictions for switch stack configuration:

- This feature is not supported on C9200CX-12P-2X2G, C9200CX-8P-2X2G, and C9200CX-12T-2X2G models of the Cisco Catalyst 9200CX Series Switches

- A switch stack can have up to eight stacking-capable switches connected through their StackWise ports.

- Only homogenous stacking is supported, that is, a stack of Cisco Catalyst 9200 Series Switches with only Cisco Catalyst 9200 Series Switches as stack members.

- You cannot have a switch stack containing a mix of different license levels.

- Do not stack Cisco Catalyst 9200L Series Switches with Cisco Catalyst 9200 Series Switches.

- C9200-24PB and C9200-48PB switch models can only be stacked with each other and not with other models of the Cisco Catalyst 9200 Series Switches.

- During a switchover, when the standby device syncs with the active device, the following log message is displayed on the console:

%SM-4-BADEVENT: Event 'standby_phy_link_up' is invalid for
the current state 'NO_NEIGHBOR': rep_lsl_rx Gix/x/x -Traceback=

Ignore this message. It does not have any functional or operational impact.

Information About Switch Stacks

- Switch Stack Overview

- Switch Stack Bridge ID and MAC Address

- Upgrading a Switch Running Incompatible Software

- Switch Stack Management Connectivity

Switch Stack Overview

A switch stack can have up to eight stacking-capable switches connected through their StackWise ports. The stack members work together as a unified system. Layer 2 and Layer 3 protocols present the entire switch stack as a single entity to the network.

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.

Switch Stack Bridge ID and MAC Address

A switch stack is identified in the network by its bridge ID and, if it is operating as a Layer 3 device, its router MAC address. The bridge ID and router MAC address are determined by the MAC address of the active switch.

If the active switch changes, the MAC address of the new active switch determines the new bridge ID and router MAC address.

If the entire switch stack reloads, the switch stack uses the MAC address of the active switch.

- Persistent MAC Address on the Switch Stack

Persistent MAC Address on the Switch Stack

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 active switch rejoins the stack, the stack continues to use its MAC address as the stack MAC address, even if the switch is now a stack member and not an active switch. If the previous active switch does not rejoin the stack during this period, the switch stack takes the MAC address of the new active switch as the stack MAC address. By default, the stack MAC address will be the MAC address of the first active switch, even if a new active switch takes over.

You can use the persistent MAC address feature to set a time delay before the stack MAC address changes to the MAC address of the new stack master. When this feature is enabled, the stack MAC address changes in approximately 4 minutes. During this time, if the previous stack master rejoins the stack, the stack continues to use its 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.

Note

You can also configure stack MAC persistency so that the stack MAC address never changes to the new active switch MAC address, by using the stack-mac persistent timer 0 command. This avoids Link Aggregation Control Protocol (LACP) and Port Aggregation Protocol (PAgP) flaps or inconsistencies.

Upgrading a Switch Running Incompatible Software

The auto-upgrade and auto-advise features enable a switch with software packages that are incompatible with the switch stack to be upgraded to a compatible software version so that it can join the switch stack.

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 any of the supported network management applications. You cannot manage stack members on an individual basis.

How to Configure a Switch Stack

- Monitoring the Device Stack

Monitoring the Device Stack

Commands for Displaying Stack Information

Command

Description

show module

Displays summary informaton about the stack.

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.

show switch stack-ports [detail]

Displays the stack link status and information for each stack member. Use the detail keyword to display the stack interface status, errors, drops, packet transmission and bandwidth details.

show redundancy

Displays the redundant system and the current processor information. The redundant system information includes the system uptime, standby failures, switchover reason, hardware, configured and operating redundancy mode. The current processor information displayed includes the active location, the software state, the uptime in the current state and so on.

show redundancy state

Displays all the redundancy states of the active and standby devices.

Configuration Examples for Switch Stacks

- Switch Stack Configuration Scenarios

- Enabling the Persistent MAC Address Feature: Example

- show switch stack-ports summary Command Output: Example

- show switch stack-ports detail Command Output: Example

- Software Loopback: Examples

- Additional References for Switch Stacks

Switch Stack Configuration Scenarios

Most of these switch stack configuration scenarios assume that at least two devices are connected through their StackWise ports.

Configuration Scenarios

Scenario

Result

Active switch election specifically determined by existing active switches

Connect two powered-on switch stacks through the StackWise ports.

Only one of the two active switches becomes the new active switch.

Active switch election specifically determined by the stack member priority value

1. Connect two switches through their StackWise ports.

2. Use the switch stack-member-number priority new-priority-number command to set one stack member with a higher member priority value.

3. Restart both member switches at the same time.

The stack member with the higher priority value is elected active switch.

Active switch election specifically determined by the configuration file

Assuming that both member switches have the same priority value:

1. Make sure that one stack member has a default configuration and that the other stack member has a saved (nondefault) configuration file.

2. Restart both member switches at the same time.

The stack member with the saved configuration file is elected active switch.

Active switch election specifically determined by the MAC address

Assuming that both member switches have the same priority value, configuration file, and license level, restart both member switches 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:

1. Ensure that both member switches have the same stack member number. If necessary, use the switch current-stack-member-number renumber new-stack-member-number command.

2. Restart both member switches at the same time.

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

1. Power off the new switch.

2. Through their StackWise ports, connect the new switch to a powered-on switch stack.

3. Power on the new switch.

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 member switches becomes the new active switch. All other member switches in the stack remain as member switches and do not reboot.

Add member switches

1. Through their StackWise ports, connect devices.

2. Power on all devices.

Two devices become active switches. One active switch has member switches. The other active switch remains as a standalone device.

Use the Mode button and port LEDs on the device to identify which devices are active switches and which devices belong to each active switch.

Enabling the Persistent MAC Address Feature: Example

This example shows how to configure the persistent MAC address feature for a 7-minute time delay and to verify the configuration:

Device(config)# stack-mac persistent timer 7
WARNING: The stack continues to use the base MAC of the old active
WARNING: as the stack-MAC after a active 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.
Device(config)# end
Device# 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     Ready

show switch stack-ports summary Command Output: Example

Only Port 1 on stack member 2 is disabled.

# show switch stack-ports summary
#/  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

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.

- Down—A cable is detected, but either no connected neighbor is up, or the stack port is disabled.

- OK—A cable is detected, and the connected neighbor is up.

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.

When there is no cable connected to the stack port, the value displayed is no cable along with the cable length value.

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.

- No—There is no stack cable connected to this port or the stack cable is not functional.

- Yes—There is a functional stack cable connected to this port.

Link Active

Whether a neighbor is connected on the other end of the stack cable.

- No—No neighbor is detected on the other end. The port cannot send traffic over this link.

- Yes—A neighbor is detected on the other end. The port can send traffic over this link.

Sync OK

Whether the link partner sends valid protocol messages to the stack port.

- No—The link partner does not send valid protocol messages to the stack port.

- Yes—The link partner sends valid protocol messages to the 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.

- No—At least one stack port on the member has an attached stack cable.

- Yes—None of the stack ports on the member has an attached stack cable.

show switch stack-ports detail Command Output: Example

The following is a sample output of the command for a working stack:

Device# show switch stack-ports detail
1/1 is DOWN Loopback No
Cable Length 50cm     Neighbor NONE
Link Ok Yes Sync Ok Yes Link Active No
Changes to LinkOK 1
Five minute input rate  0 bytes/sec
Five minute output rate 0 bytes/sec
752 bytes input
240 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 667
1/2 is OK Loopback No
Cable Length 50cm     Neighbor 3
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 1
Five minute input rate  7 bytes/sec
Five minute output rate 0 bytes/sec
54332 bytes input
1120 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 0
2/1 is OK Loopback No
Cable Length 50cm     Neighbor 3
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 1
Five minute input rate  0 bytes/sec
Five minute output rate 30 bytes/sec
146390 bytes input
217587 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 0
2/2 is DOWN Loopback No
Cable Length 50cm     Neighbor NONE
Link Ok Yes Sync Ok Yes Link Active No
Changes to LinkOK 1
Five minute input rate  0 bytes/sec
Five minute output rate 0 bytes/sec
1208 bytes input
480 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 0
3/1 is OK Loopback No
Cable Length 50cm     Neighbor 1
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 1
Five minute input rate  0 bytes/sec
Five minute output rate 0 bytes/sec
41245 bytes input
240 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 0
3/2 is OK Loopback No
Cable Length 50cm     Neighbor 2
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 1
Five minute input rate  10 bytes/sec
Five minute output rate 0 bytes/sec
60412 bytes input
480 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 0

show switch stack-ports detail Command Output

Field

Description

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 Unknown. 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.

- No: There is no stack cable connected to this port or the stack cable is not functional.

- Yes: There is a functional stack cable connected to this port.

Link Active

Whether a neighbor is connected on the other end of the stack cable.

- No: No neighbor is detected on the other end. The port cannot send traffic over this link.

- Yes: A neighbor is detected on the other end. The port can send traffic over this link.

Sync OK

Whether the link partner sends valid protocol messages to the stack port.

- No: The link partner does not send valid protocol messages to the stack port.

- Yes: The link partner sends valid protocol messages to the 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.

Five minute input rate

The average rate (calculated over a five minute period) at which packets are received, measured in packets/sec.

Five minute output rate

The average rate (calculated over a five minute period) at which packets are transmitted, measured in packets/sec.

CRC Errors

Different types of Cyclic Redundancy Check (CRC) errors that are seen on a stack interface:

- Data CRC: Stack interface data CRC error

- Ringword CRC: Stack interface ring word CRC error

- InvRingWord: Stack interface invalid ring word error

- PcsCodeWord: Stack interface Physical Coding Sublayer (PCS) error

These errors normally occur when a stack interface state changes due to a switchover or a switch reload. You can ignore such errors.

But when these error counters increase significantly or when they increase continuously over a period of time, check the stack cable for issues.

he following is a sample output when the stack port flaps:

Device# show switch stack-ports detail
1/1 is OK Loopback No
Cable Length 50cm     Neighbor 2
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 4
Five minute input rate  0 bytes/sec
Five minute output rate 0 bytes/sec
320 bytes input
80 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 770
1/2 is OK Loopback No
Cable Length 50cm     Neighbor 3
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 1
Five minute input rate  5 bytes/sec
Five minute output rate 1 bytes/sec
2949 bytes input
320 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 0
2/1 is OK Loopback No
Cable Length 50cm     Neighbor 3
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 1
Five minute input rate  0 bytes/sec
Five minute output rate 0 bytes/sec
49375 bytes input
160 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 0
2/2 is OK Loopback No
Cable Length 50cm     Neighbor 1
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 2
Five minute input rate  0 bytes/sec
Five minute output rate 0 bytes/sec
1824 bytes input
160 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 0
3/1 is OK Loopback No
Cable Length 50cm     Neighbor 1
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 1
Five minute input rate  372 bytes/sec
Five minute output rate 7 bytes/sec
111876 bytes input
4613 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 0
3/2 is OK Loopback No
Cable Length 50cm     Neighbor 2
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 2
Five minute input rate  0 bytes/sec
Five minute output rate 0 bytes/sec
80 bytes input
0 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 0

The following is a sample output when a switch reloads:

Device#show switch stack-ports detail
1/1 is OK Loopback No
Cable Length 50cm     Neighbor 2
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 5
Five minute input rate  0 bytes/sec
Five minute output rate 0 bytes/sec
2032 bytes input
320 bytes output
CRC Errors
Data CRC 184
Ringword CRC 187
InvRingWord  120
PcsCodeWord 112
1/2 is OK Loopback No
Cable Length 50cm     Neighbor 3
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 1
Five minute input rate  2 bytes/sec
Five minute output rate 0 bytes/sec
24164 bytes input
800 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 0
2/1 is OK Loopback No
Cable Length 50cm     Neighbor 3
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 1
Five minute input rate  0 bytes/sec
Five minute output rate 0 bytes/sec
3024 bytes input
240 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 0
2/2 is OK Loopback No
Cable Length 50cm     Neighbor 1
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 1
Five minute input rate  7 bytes/sec
Five minute output rate 0 bytes/sec
9148 bytes input
480 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 0
3/1 is OK Loopback No
Cable Length 50cm     Neighbor 1
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 1
Five minute input rate  0 bytes/sec
Five minute output rate 15 bytes/sec
1509354 bytes input
27853 bytes output
CRC Errors
Data CRC 0
Ringword CRC 0
InvRingWord  0
PcsCodeWord 0
3/2 is OK Loopback No
Cable Length 50cm     Neighbor 2
Link Ok Yes Sync Ok Yes Link Active Yes
Changes to LinkOK 3
Five minute input rate  0 bytes/sec
Five minute output rate 0 bytes/sec
240 bytes input
160 bytes output
CRC Errors
Data CRC 118
Ringword CRC 74
InvRingWord  125
PcsCodeWord 373

Software Loopback: Examples

In a stack with three members, stack cables connect all the members:

# show switch stack-ports summary
#
Sw#/Port#  Port    Neighbor  Cable     Link  Link    Sync   #Changes   In
Status            Length    OK    Active  OK     To LinkOK  Loopback
--------  ------  --------  --------  ----  ------  ----  ---------   --------
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        No

If 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

# show switch stack-ports summary
#
Sw#/Port#  Port    Neighbor  Cable     Link  Link    Sync  #Changes   In
Status            Length    OK    Active  OK    To LinkOK  Loopback
--------  ------  --------  --------  ----  ------  ----  ---------  --------
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        No

If 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:

# show sw stack-ports summary
#
Sw#/Port#  Port    Neighbor  Cable     Link  Link    Sync  #Changes   In
Status            Length    OK    Active  OK    To LinkOK  Loopback
--------  ------  --------  --------  ----  ------  ----  ---------  --------
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        No

Switch 1 is a standalone switch:

# show switch stack-ports summary
#
Sw#/Port#  Port    Neighbor  Cable     Link  Link    Sync  #Changes   In
Status            Length    OK    Active  OK    To LinkOK  Loopback
--------  ------  --------  --------  ----  ------  ----  ---------  --------
1/1     Absent    None    No cable  No     No     No         1        Yes
1/2     Absent    None    No cable  No     No     No         1        Yes

- Software Loopback with Connected Stack Cables: Examples

- Software Loopback with no Connected Stack Cable: Example

- Finding a Disconnected Stack Cable: Example

- Fixing a Bad Connection Between Stack Ports: Example

Software 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.

# show switch stack-ports summary
#
Sw#/Port#  Port    Neighbor  Cable     Link  Link    Sync  #Changes   In
Status            Length    OK    Active  OK    To LinkOK  Loopback
--------  ------  --------  --------  ---- ------  ----  ---------  --------
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

- Cables on a switch that is running properly

- Stack ports with a cable that works properly

# show switch stack-ports summary
#
Sw#/Port#  Port    Neighbor  Cable     Link  Link    Sync  #Changes   In
Status            Length    OK    Active  OK    To LinkOK  Loopback
--------  ------  --------  --------  ----  ------  ----  ---------  --------
2/1       OK       2      50 cm     Yes    Yes    Yes       1         No
2/2       OK       2      50 cm     Yes    Yes    Yes       1         No

The port status shows that

- Switch 2 is a standalone switch.

- The ports can send and receive traffic.

Software Loopback with no Connected Stack Cable: Example

# show switch stack-ports summary
#
Sw#/Port#  Port    Neighbor  Cable     Link  Link    Sync  #Changes   In
Status            Length    OK    Active  OK    To LinkOK  Loopback
--------  ------  --------  --------  ----  ------  ----  ---------  --------
1/1     Absent    None    No cable   No     No     No       1         Yes
1/2     Absent    None    No cable   No     No     No       1         Yes

Finding 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:

# show switch stack-ports summary
#
Sw#/Port#  Port    Neighbor  Cable     Link  Link    Sync  #Changes   In
Status            Length    OK    Active  OK    To LinkOK  Loopback
--------  ------  --------  --------  ----  ------  ----  ---------  --------
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        No

If 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 DOWN

This is now the port status:

# show switch stack-ports summary
#
Sw#/Port#  Port    Neighbor  Cable     Link  Link    Sync  #Changes   In
Status            Length    OK    Active  OK    To LinkOK  Loopback
--------  ------  --------  --------  ----  ------  ----  ---------  --------
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        No

Only 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:

- Verify the cable connection for Port 2 on Switch 1.

- Port 2 on Switch 1 has a port or cable problem if

- The In Loopback value is Yes.

or

- The Link OK, Link Active, or Sync OK value is No.

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:

# show switch stack-ports summary
#
Sw#/Port#  Port    Neighbor  Cable     Link  Link    Sync  #Changes   In
Status            Length    OK    Active  OK    To LinkOK  Loopback
--------  ------  --------  --------  ----  ------  ----  ---------  --------
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          No

Diagnosing 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

Related Documents

Related Topic

Document Title

Cabling and powering on a switch stack.

Cisco Catalyst 9200 Series Switches Hardware Installation Guide

SGACL High Availability

"Cisco TrustSec SGACL High Availability" module of the Cisco TrustSec Switch Configuration Guide

Error Message Decoder

Description

Link

To help you research and resolve system error messages in this release, use the Error Message Decoder tool.

https://www.cisco.com/cgi-bin/Support/Errordecoder/index.cgi

Standards and RFCs

Standard/RFC

Title

None

—

MIBs

MIB

MIBs Link

All the supported MIBs for this release.

To locate and download MIBs for selected platforms, Cisco IOS releases, and , use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

Technical Assistance

Description

Link

The Cisco Support website provides extensive online resources, including documentation and tools for troubleshooting and resolving technical issues with Cisco products and technologies.

To receive security and technical information about your products, you can subscribe to various services, such as the Product Alert Tool (accessed from Field Notices), the Cisco Technical Services Newsletter, and Really Simple Syndication (RSS) Feeds.

Access to most tools on the Cisco Support website requires a Cisco.com user ID and password.

http://www.cisco.com/support

Feature History for Switch Stacks

This table provides release and related information for features explained in this module.

These features are available on all releases subsequent to the one they were introduced in, unless noted otherwise.

Release

Feature

Feature Information

Cisco IOS XE Fuji 16.9.1

Switch Stack

A switch stack can have up to eight stacking-capable switches connected through their StackWise ports. The stack members work together as a unified system. Layer 2 and Layer 3 protocols present the entire switch stack as a single entity to the network.

Cisco IOS XE Amsterdam 17.2.1

Switch Stack

C9200-24PB and C9200-48PB switch models can only be stacked with each other and not with other models of the Cisco Catalyst 9200 Series Switches.

Cisco IOS XE Amsterdam 17.3.1

Switch Stack

A new command show switch stack-ports detail was introduced to display detailed information on the stack link of each stack member.

Use the Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to https://cfnng.cisco.com/. An account on Cisco.com is not required

Chapter 2. Configuring 1:1 Redundancy

Enabling the 1:1 redundancy stack mode allows you to assign active and standby roles to specific switches in the stack.

- Prerequisites for 1:1 Redundancy

- Information About 1:1 Redundancy

- How to Configure 1:1 Redundancy

- Verifying the Stack Mode

- Configuration Examples for 1:1 Redundancy

- Additional References for 1:1 Redundancy

- Feature History for 1:1 Redundancy

Prerequisites for 1:1 Redundancy

The following are prerequisites for 1:1 redundancy:

- All the switches in the stack must be running the same license level as the active switch. For information about license levels, see the System Management Configuration Guide of the required release.

- All the switches in the stack must be running compatible software versions.

Information About 1:1 Redundancy

1:1 redundancy is used to assign active and standby roles to specific switches in the stack. This overrides the traditional N+1 role selection algorithm, where any switch in the stack can be active or standby. In 1:1 redundancy, the stack manager determines the active and standby role for a specific switch, based on the flash ROMMON variable. The algorithm assigns one switch as active, another switch as standby, designating all remaining switches in the stack as members. When an active switch reboots it becomes standby and the existing standby switch becomes the new active. The existing member switches remain in the same state.

How to Configure 1:1 Redundancy

- Enabling 1:1 Redundancy Stack Mode

- Disabling 1:1 Redundancy Stack Mode

Enabling 1:1 Redundancy Stack Mode

Follow these steps to enable the 1:1 redundancy stack mode, and set a switch as the active switch in a stack, or as the standby:

Procedure

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode. Enter your password if prompted.

Step 2

switch switch-number role{ active| standby}

Example:

Device# switch 1 role active

Changes stack mode to 1:1 mode and designates the switch as active or standby.

Disabling 1:1 Redundancy Stack Mode

On a switch where 1:1 redundancy is enabled, follow these steps to disable the feature. This changes the stack mode to N+1:

Procedure

Step 1

enable

Example:

Device> enable

Enables privileged EXEC mode. Enter your password if prompted.

Step 2

switch clear stack-mode

Example:

Device# switch clear stack-mode

Changes stack mode to the N+1 mode and removes active and standby assignments.

Verifying the Stack Mode

To verify the current stack mode on a switch, enter the show switch stack-mode command in priviledged EXEC mode. The output displays detailed status of the currently running stack mode.

Device# show switch stack-mode
Switch   Role    Mac Address    Version   Mode    Configured   State
---------------------------------------------------------------
1       Member 3c5e.c357.c880             1+1'     Active'     Ready
*2      Active 547c.69de.cd00    V05      1+1'     Standby'    Ready
3       Member 547c.6965.cf80    V05      1+1'     Member'     Ready

The Mode field indicates the current stack mode

The Configured field refers to the switch state expected after a reboot.

Single quotation marks ( ' ) indicate that the stack mode has been changed.

Configuration Examples for 1:1 Redundancy

- Example: Enabling 1:1 Redundancy Stack Mode

- Example: Disabling 1:1 Redundancy

Example: Enabling 1:1 Redundancy Stack Mode

You can use the switch switch-number role command to set the active and standby switch in 1:1 stack mode. The stack operates in the 1:1 stack mode with the specified active or standby after reboot. In the following example, switch 1 is assigned the active role, and switch 2 is assigned the standby role.

Device# switch 1 role active
WARNING: Changing the switch role may result in redundancy mode being configured to 1+1 mode for this stack. If the configured Active or Standby switch numbers do not boot up, then the stack will not be able to boot. Do you want to continue?[y/n]? [yes]: yes

Device# switch 2 role standby
WARNING: Changing the switch role may result in redundancy mode being configured to 1+1 mode for this stack. If the configured Active or Standby switch numbers do not boot up, then the stack will not be able to boot. Do you want to continue?[y/n]? [yes]: yes

Example: Disabling 1:1 Redundancy

You can use the switch clear stack-mode command to remove 1:1 stack mode, and change it back to N+1 stack mode.

Device# switch clear stack-mode
WARNING: Clearing the chassis HA configuration will resultin the chassis coming up in Stand Alone mode after reboot.The HA configuration will remain the same on other chassis. Do you wish to continue? [y/n]? [yes]:

Additional References for 1:1 Redundancy

Related Documents

Related Topic

Document Title

For complete syntax and usage information for the commands used in this chapter.

See the Stacking and High Availability Commands section of the Command Reference for the release.

Feature History for 1:1 Redundancy

This table provides release and related information for features explained in this module.

These features are available on all releases subsequent to the one they were introduced in, unless noted otherwise.

Release

Feature

Feature Information

Cisco IOS XE Fuji 16.9.2

1:1 Redundancy

Enables the 1:1 redundancy stack mode and enables you to assigns active and standby roles to specific switches in the stack.

Use Cisco Feature Navigator to find information about platform and software image support. To access Cisco Feature Navigator, go to https://cfnng.cisco.com.

Chapter 3. Troubleshooting Stacking and High Availability

- Overview

- Support Articles

- Feedback Request

- Disclaimer and Caution

Overview

This chapter provides links to documents authored by Cisco subject matter experts (SMEs). They aim to help you resolve technical issues without requiring a support ticket. If these documents are unable to resolve your issue, we recommend visiting the applicable Cisco Community. There is a wealth of information and advice available from fellow Cisco customers who may have experienced this issue already and provided a solution. If you are not able to find a resolution on the Community, it may be best that you raise a support ticket at Cisco Support. In cases where a support ticket has to be raised, these documents provide guidance about the data that should be collected and added to the support ticket. Specify the support document you referred, and TAC can create an improvement request with the document owner.

Support Articles

The documents in this section were created using specific software and hardware listed in the Components Used section of each article. However, this does not mean that they are limited to what is listed in Components Used, and generally remain relevant for later versions of software and hardware. Note that there could be some changes in the software or hardware that can cause commands to stop working, the syntax to change, or GUIs and CLIs to look different from one release to another.

The following are the support articles associated with this technology:

Document

Description

Verify and Troubleshoot Stackwise on Catalyst 9200/9300

This document describes how to troubleshoot common failure scenarios in Stackwise deployments of Catalyst 9200/9200L, 9300/9300L and 9300X switches.

Troubleshoot Catalyst 9200/9300 Reloads Due to Stack Issues

This document describes how to troubleshoot unexpected reloads due to stack issues on Catalyst 9000 switches.

Feedback Request

Your input helps. A key aspect to improving these support documents is customer feedback. Note that these documents are owned and maintained by multiple teams within Cisco. If you find an issue specific to the document (unclear, confusing, information missing, etc):

- Provide feedback using the Feedback button located at the right panel of the corresponding article. The document owner will be notified, and will either update the article, or flag it for removal.

- Include information regarding the section, area, or issue you had with the document and what could be improved. Provide as much detail as possible.

Disclaimer and Caution

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, ensure that you understand the potential impact of any command.

Full Cisco Trademarks with Software License

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The Cisco implementation of TCP header compression is an adaptation of a program developed by the University of California, Berkeley (UCB) as part of UCB's public domain version of the UNIX operating system. All rights reserved. Copyright © 1981, Regents of the University of California.

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IN NO EVENT SHALL CISCO OR ITS SUPPLIERS BE LIABLE FOR ANY INDIRECT, SPECIAL, CONSEQUENTIAL, OR INCIDENTAL DAMAGES, INCLUDING, WITHOUT LIMITATION, LOST PROFITS OR LOSS OR DAMAGE TO DATA ARISING OUT OF THE USE OR INABILITY TO USE THIS MANUAL, EVEN IF CISCO OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE POSSIBILITY OF SUCH DAMAGES.

Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

All printed copies and duplicate soft copies of this document are considered uncontrolled. See the current online version for the latest version.

Cisco has more than 200 offices worldwide. Addresses and phone numbers are listed on the Cisco website at www.cisco.com/go/offices.

The documentation set for this product strives to use bias-free language. For purposes of this documentation set, bias-free is defined as language that does not imply discrimination based on age, disability, gender, racial identity, ethnic identity, sexual orientation, socioeconomic status, and intersectionality. Exceptions may be present in the documentation due to language that is hardcoded in the user interfaces of the product software, language used based on standards documentation, or language that is used by a referenced third-party product.

Cisco and the Cisco logo are trademarks or registered trademarks of Cisco and/or its affiliates in the U.S. and other countries. To view a list of Cisco trademarks, go to this URL: https://www.cisco.com/c/en/us/about/legal/trademarks.html. Third-party trademarks mentioned are the property of their respective owners. The use of the word partner does not imply a partnership relationship between Cisco and any other company. (1721R)