VS-S720-10G-3C with WS-SUP720-3B for redundancy

Unanswered Question
May 27th, 2008

Hello,

We have a dual chassis core with single sup 720-3B's. I am planning on upgrading them to dual sup 720-10G-3C's without VSS for the time being. So the question is can I do a zero downtime upgrade by installing the 3C sup in with the existing 3B and create a working failover scenario. At which point I would pull the 3B and add the second 3C effectively causing no downtime. Thoughts on this would be greatly appreciated. Thanks.

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amritpatek Mon, 06/02/2008 - 05:43

Yes you can do this. VSS is only an option with this supervisor, you can also use it like any other Sup720.

Ryan Carretta Tue, 06/03/2008 - 00:28

You probably won't be able to do this.

For starters, what version of code are you running on that Sup720? Unless its something in the 12.2(33)SXH train already, you'd need to upgrade to something in that train to support the VS-S720-10G.

Aside from that, the VS-S720-10G has a radically different architecture than the WS-SUP720-3B. I can say for certain the ASICs responsible for the switch fabric are different, and they have different mechanisms for syncing up the fabric. Additionally, the PFC version on the VS-S720 would have to fall back to PFC-3B to interface with the Sup720 (assuming that's even possible). I don't think it would reinitialize to PFC-3C even if you then yanked the Sup720 out of the chassis.

I think you would be much better off with a planned maintenance window where you can pull the sup safely and upgrade then.

Ryan Carretta Tue, 06/03/2008 - 01:56

It just occurred to me that perhaps you are okay with *one* of the core chassis being down at a time. If this is the case, you would be able to just bring one chassis offline at a time, install the sup, bring it back online, etc. There would be some interruption in service doing it this way while things reconverged. My above post was assuming you were trying to do the swap in the same chassis.

ralphcarter Tue, 06/03/2008 - 04:44

rcarret,

Will the sup720-3b and the C work together for redundancy in a single chasis? If the C fails, would the 3b take over? How would that work if its virtualized?

Ryan Carretta Tue, 06/03/2008 - 09:11

What Yogesh said.

Additionally, the Sup720-3B doesn't support switch virtualization (VSS) so that wouldn't be possible anyhow.

I would be surprised if inserting this sup in your operating box didn't crash the switch outright.

jasonmcl Tue, 06/03/2008 - 10:30

VSS was not an issue for the time being as it does not support dual sup's. We did not try to do anything funny. We simply prestaged the sups offline shut down the core and brought it back up on the 3c's. Total downtime 22 minutes. Core now channeled at 20Gig. Thanks for all the feedback. Would have been cool to be able to do a zero downtime upgrade but hey cant have it all. Peace!

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