VSS with multiple supervisor engines

[Colin Higgins]

Is it possible to do VSS between multipe supervisor 2T engines? (I have only seen configurations using one in each switch)

Is there an advantage?

[Reza Sharifi · Accepted solution]

It has been a long time that Cisco has try to publish quad sup VSS.  According to this link it is supported staring 15.1(1), but I don't think that many people have actually deployed it since the IOS version is pretty new. The biggest issue in the past was that with 2 sups in each chassis when one of the sup on the primary failed, it would switch over to the stand-by sup, which defeats the purpose of having 2 sup in each chassis.  It will be interesting to know if anyone has actually tested this with this new IOS and it works the way it should.

http://www.cisco.com/en/US/docs/switches/lan/catalyst6500/ios/15.1SY/config_guide/sup2T/virtual_switching_systems.html#wp1317162

HTH

[Colin Higgins]

I looked at some documentation and demos, and it looked complicated and potentially pointless. I will stick with the standard VSS setup.

[Joseph W. Doherty]

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Posting

Quad VSS provides two advantages.  If you lose a sup in a chassis, you don't lose the whole chassis (and all the bandwidth that it's supporting).  Also, in cases where you might have single homed connections on a VSS pair, it avoids the sup on the hosting chassis being a single point of failure for those.

[Colin Higgins]

Joseph (or anyone)

Where can I go to see how to configure Quad-VSS? I see it mentioned in the VSS configuration guide, but I don't know:

a) Where are the 3rd and 4th supervisor modules connected to? Each other? Are they cross-connected to the existing supervisor modules?

b) Once the switches are converted (virtualized) how is supervisor failover configured and handled?

[Reza Sharifi · Accepted solution]

There is some good info for Quad Sup VSS in this presentation

http://www.cisco.com/web/learning/le21/le39/docs/tdw181_prezo.pdf

a) Where are the 3rd and 4th supervisor modules connected to? Each other? Are they cross-connected to the existing supervisor modules?

Yes, the recommendation is to use one 10Gig from each sup. If you want to put 4 10Gig in your vsl link then 2 10Gig from each sup.

b) Once the switches are converted (virtualized) how is supervisor failover configured and handled?

see presentation

HTH

[InayathUlla Sharieff]

Reza,

Unfortunately I dont have much data on this to share with you. Once I am done with my testing or get hold of the issues will update you on the same.

Regards

Inayath

[Reza Sharifi]

Thanks Inayath!!!

I am very interested in knowing how the sup fail over actually works, when you have 2 sups in each device.

I had an opportunity to test this a few months ago, but the IOS wasn't out at that time and now all those 6500s are in production.

Reza

[Colin Higgins]

I think what has me most confused is the connectivity between the sups, and how they interact.

Say I have 4 supervisors between two 6500s, in slots 5 & 6. Two of these supervisors are going to be in this new standby state, so if we connect 10Gbs interfaces to them, are they even forwarding traffic? Or are they just exchanging heartbeats and waiting for a failure? If I cross-connect the 4 supervisors, will my available bandwidth be reduced by 50%? (instead of 2 10Gbs connections going to the 2nd supervisor that is virtualized, one is now going to a supervisor in a standby state that is not forwarding traffic).

[Leo Laohoo]

Or are they just exchanging heartbeats and waiting for a failure?

The heartbeat goes into it's own link.  Not advisable for the heartbeat to be on a 10 Gbps link.

[Colin Higgins]

But are the standby supervisors (3 & 4) forwarding traffic?

[Leo Laohoo]

If I understood correctly, all the hot standby supervisor cards forward traffic.

[Colin Higgins]

So I would put all 6 10Gbs connections into a single port-channel?

[Leo Laohoo]

On one side, you can put a maximum of eight 10 Gbps pots into a single MEC.

You also need a single 1 Gbps link to do the heartbeat.

[Colin Higgins]

Leo:

Looking at this configuration guide (which is a bit old and involves the 720), there is no heartbeat link

http://www.netcraftsmen.net/component/content/article/69-data-center/749-vss-configuration.html

Where does this link come into play?

Sorry I have so many questions on this, but I have only done a standard VSS deployment using 720s, and this quad VSS with 2Ts is all new to me.

I am also wondering if during initial setup, you define the 2nd supervisor in the chassis as redundant (like in the days before VSS) and then do the conversion. I am wondering if everything converts over normally.