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New Member

VSS upgrade for 6500's.

Is it true that when doing and IOS upgrade for 6500's that both switches go "offline" so to speak during upgrade?



Re: VSS upgrade for 6500's.

Yes, the supervisor in each switch will reload and the config will be erased and recreated using the x/y/z notation for interfaces instead of the x/y notation.


Re: VSS upgrade for 6500's.

My understanding of the IOS upgrade process is as follows. One chassis will get upgraded, and rebooted. At this time your switch will run at 50% capacity. Issue an active switchover will shut down both chassis, as the switch with the new image will take over and the old switch will get reloaded. From here, you can upgrade the other switch, reload it and you'll come back up to 100% capacity. I have a WhitePaper explaining the process very well, however I can't seem to find the link any longer.

Hope this helps, rate if it does,



Re: VSS upgrade for 6500's.

What exactly do you mean:

- convert two standalone to VSS config ?

- or upgrade a running VSS pair ?

For switches running VSS config, it used to be true that there will be a period that both switches are off-line. This period can be as long as 5 - 15 minutes. When you reload the standby with a new (different) version, the two switches will not form a VSS anymore. The standby chassis will reboot, note a difference in version and remain in RPR mode. In this mode it is online, but doing nothing. The fabric is not forwarding packets so VSS is running at 50% of bandwidth. The standby just monitors the active switch.

When you now reboot the active switch, the standby will notice this and re-initialize (!)itself as master. This re-initialize is NOT an SSO switchover, but more of a complete reload. This means you have to wait before the complete chassis (SUP+LC) boots to have connectivity again (50%). This can take a very long time if you have lots of linecards and especially if you have DFC capable LCs.

The good news is that Cisco has just released the SXI release which has ISSU (In-Service-Software-Upgrades). IF (!) the two images are ISSU compatible (!), the standby switch will not remain in RPR mode, but SSO mode, actively forwarding traffic and running with two different versions (for a short time, yes it works !) and switchover during an upgrade will be as fast as < 1 sec.

New Member

Re: VSS upgrade for 6500's.

Hello, hope you can help.. when upgrading the IOS version of the VSS do you have to load the new IOS onto both active and standby supervisor module? Or is it copied across automatically from active to standby?? The version we currently use does not support ISSU.