Sup 720 vss replacement doubts about VSL links and Preemption

[mo shea]

Hi...

Our Primary 6500 vss sup 720 has gone bad and RMA is on its way. The standby (switch 2) is now active. I have read the Cisco vss sup replacement guidelines as well as the informational discussion from Leo, Jon and Reza from the following link,

https://supportforums.cisco.com/discussion/11319676/cisco-6509-e-vss-replace-supervisor

but I still have a few doubts,

1) During the supervisor replacement for the faulty switch 1, should the VSL links and the dual active detection links remain connected to switch 2 or disconnect them? 

2) The configuration existing (from switch 2) shows that switch 1 is configured with priority and preempt. Now according to recommendation these should be removed. Shall I remove them immediately or wait till VSS is resatblished after fixing switch one?

Because I have read somewhere it is better to avoid config changes during VSS outage.

All help is appreciated.

Thanks in advance.

[Reza Sharifi · Accepted solution]

Hi,

1) During the supervisor replacement for the faulty switch 1, should the VSL links and the dual active detection links remain connected to switch 2 or disconnect them?

Yes, you can leave the VSL and dual active detection link connected.

2) The configuration existing (from switch 2) shows that switch 1 is configured with priority and preempt. Now according to recommendation these should be removed. Shall I remove them immediately or wait till VSS is resatblished after fixing switch one?

I would recommend removing the preemption and priority after both switches are up and running and VSS is established.  You don't want to make changes in one switch and not replicate to the other one because it is out of service. Overall, you should not make any changes during the outage.

HTH

[mo shea]

Thanks Reza for the answer.

This means probably I have to wait until switch two reboots as the faulty switch one re establishes itself as the active switch once fixed, probably 25 mins after fixing switch one (switch 1 needs 10-15mins to load and sync after sup replacement, plus another 10 - 15 mins for switch 2 to reload to become secondary, then remove preempt and priority from config, right?

[Reza Sharifi · Accepted solution]

That is correct Mo.

There is really no need for priority and preemption, as deploying it causes more reboot and longer recovery time. In VSS environment, both switch will forward anyway. Once the VSS established and you remove the commands and save the config, you will be good to go. 

Good Luck