Understanding Switch Stacking
Switch stacking is a technology which will allow multiple switches to become a single logical switch. Which will allow you to manage them as a single switch. Cisco has Stackwise. Stackwise architecture allows stacking up to eight switches. Other Vendors has their own stacking technology which is similar. In this discussion, we are only going to go through adding a Cisco 9300 to a Cisco 9300X Stack.
Planning Your Switch Stack.
The initial steps are to plan a switch stack. Requirements are below.
- identify your switch models and make sure they are compatible and supported.
- Make sure each switch is running on the same software.
- Connect your stackwise cable to create a ring.
Commonly people with stack with the same model switches. Others will stack their existing switches will newly switches. Like the Cisco 9300X with the Cisco 9300. Cisco calls it a mix stack.
We ran into an issue when we added some Cisco 9300 to a stacked with Cisco 9300X.
There was some Cisco 9300 that was decommissioned from a closed site and decide to be added to an existing Cisco 9300X stack. The Cisco 9300 Switches did not join the stack. We went through the basic troubleshooting steps. Check the software and the stackwise cable. Check switch priorities. Logs show sdm template mismatch.
We discover the Cisco 9300 supports a lower stack speed than the Cisco 9300X. Cisco 9300X supports 1T stack speed. Cisco 9300 supports 480G stack speed.
To have the Cisco 9300 join the Cisco 9300X stack, we had to lower the stack speed on the Cisco 9300X.
A reload is required.
Check your switch priorities to make sure your active switch remains active after reboot. Command below.
- Show switch
If needed, change your priority with the command below.
- Switch 1 priority 15 (example of switch 1 being your active switch. Priority 15 is the highest. Range 1-15)
Change stack speed command below on the Cisco 9300X stack.
- Switch stack-speed low
Verify the Cisco 9300 has joined the stack using the command below.
- Show switch
Change your switch priorities for the new switch using the command below.
- Switch 5 priority 5 (example of switch 5 with priority 5. Priority ranges from 1-15. Don’t should a priority higher than your active switch. )
Conclusion:
I ran into this issue in October 2023. Cisco updated their documentation on November 1, 2023. Link is below. This is only an issue if you add Cisco 9300 to a Cisco 9300X stack. If it was the other way around for a Cisco 9300X to add to a Cisco 9300 stack. Cisco 9300X will automatically lower its speed to match. Click here for Cisco's documentation.
As always if you have any questions on your network configuration and would like to schedule a free consultation with us, please reach out to us at sales@lookingpoint.com and we’ll be happy to help!
Kenny Wong, Engineer