Catalyst 9300 StackWise Troubleshooting: Split Stacks

StackWise faults on the Catalyst 9300 family are rarely subtle. Either a member reloads unexpectedly, a new switch refuses to join, or a stack splits into sub-rings when a cable or a member is disturbed. This article covers the verification commands and the three failure modes Cisco documents most often, along with the mixing rules for StackWise-1T, -480 and -320 that decide whether a stack will even form.

Stack Health Baseline

show switch
show switch detail
show switch stack-ports
show switch stack-ring speed
show switch stack-ring activity

show switch detail is the one to read first: it lists each member's role (Active, Standby, Member), MAC, priority, state and both stack ports. Ring versus chain mode appears in the stack-ring speed output - a chain still works, but ring gives the resilience the design assumes.

Mixing Rules That Decide Membership

• C9300 (modular uplink) members run StackWise-480; C9300L/9300LM fixed-uplink members run StackWise-320; C9300X runs StackWise-1T.
• Fixed-uplink and modular-uplink models cannot be stacked together at all.
• Mixing C9300X with C9300 is allowed, but the stack drops to StackWise-480 speeds.
• C9300 higher-scale SKUs (C9300-24UB, 24UXB, 48UB) do not mix with standard C9300 or C9300X.
• Members must run the same IOS-XE version, the same licence level and the same install versus bundle mode.

Failure 1 - A Member Reloads Unexpectedly

show logging | include STACK
show switch detail
show environment all
show platform

Correlate the reload timestamp in show logging with the stack event, then check power: a member whose PSU is oversubscribed or whose StackPower ring is unhealthy can be reset by the stack itself. Also confirm the reload was not triggered by an image mismatch during an auto-upgrade attempt.

Failure 2 - New Switch Refuses to Join

show switch stack-ports
show version
show boot
show license summary

Join failures are almost always a mismatch: different IOS-XE build, different licence (Network Essentials against Advantage), different operational mode, or a duplicate switch number inherited from a previous life. Match the version and licence, then apply auto-upgrade from the Active switch if you cannot patch the newcomer first. Never cable a powered-on switch into a powered-on production stack - that is how split stacks and duplicate switch numbers get created.

Failure 3 - Mixed C9300X Stack Splits into Sub-Rings

The documented symptom is a 9300X mixed stack that breaks into sub-rings with mismatched stack speeds after a member is added or replaced. Read show switch stack-ring speed on every member; if one shows a different ring speed, the stack will not form a single logical switch. The resolution is to reconcile the speed domain - either bring all members to the same supported speed profile or separate the 9300X members into their own stack.

Related Design Decisions

If the stack keeps splitting, question the design before the cabling: high availability with two separate stacks plus a virtual pairing may fit better than an eight-member ring in one closet. The trade-offs are compared in StackWise versus StackWise Virtual, the bandwidth tiers are explained in StackWise-320/480/1T bandwidth, and the software-side equivalent operation is in IOS-XE install mode upgrade.

原文链接：https://www.cisco.com/c/en/us/support/docs/switches/catalyst-9300-series-switches/217684-verify-and-troubleshoot-stackwise-on-cat.pdf