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Dual Sup presence in the VSS domain


We have dual sup engine in the VSS domain (6513). For real implementation I cannot find much of information related to this. I need some guideline or help in clarifying these gaps:

1)      Cisco document mentions that the failover across the sup engine in the VSS domain is stateful. I understood this.

2)      The second sup engine acts like a DFC line card as mentioned in the document. Can you please give us more information on this.

3)      When the active sup in the vss domain fails, the standby sup in the other switch takes over. Then what is the role of the standby sup in the active chasis. Does that takes over or it is there only for VSL links.

In summary: i am unable to understand how 2 SUP in each chassis will work in VSS??

VIP Super Bronze

Re: Dual Sup presence in the VSS domain


You are correct.  There is not really many documents out there explaining this.  I guess part of it is that this is very new and supported in SXI4 and later.

Here are the steps that supposed to happen in case of a sup failure:

1-Active VSS supervisor incurs a hardware failure

2-SSO failover to the hot-standby supervisor in switch-2

3- Switch-1 reloads and comes back online

4-50% bandwidth is available during switch-1 reload

5-Switch-1 comes online

6-Previous RPR warm supervisor resumes SSO hot standby state

7-The failed supervisor boots up in RPR warm mode.

8-100% Bandwidth is available  leveraging both switches



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