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Normal Stack vs VSS

yasir shaikh

What is differences between stack vs VSS....??

7 Replies 7

Philip D'Ath

I went to reply to this and after a short while I came to the conclusion - not much.  Functionality is very similar.

Stacking tends to be done with smaller switches, and VSS on bigger switches.

Stacking tends to us special stacking cables and/or modules.  VSS tends to use "ordinary" Ethernet style ports (such as 10Gbe, 40Gbe, etc).

ok fine 

i have a doubt regarding VSS implementation . suppose that my VSL link goes down then what will happend...?

You would implement a separate DAD link to prevent both supervisors becoming active.

Joseph W. Doherty
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There are some differences.  Besides those that Philip already noted, VSS is limited to two members, while Cisco stacking switches can usually include up to nine members.  Optimal design, for VSS, traffic should not cross between VSS members, except in failure situations, where stacks use their ring links somewhat like an internal chassis bus.

In answer to your question about what happens if you lose the VSL link, well if you loose all the dedicated connections between the two VSS members, the two VSS member will partition themselves believing their partner has failed.  This is somewhat similar if all stack links are lost between some stack members, where the stack will partition itself, each member, or still joined stack members, consider themselves the stack.

Dear Friend,

I Agree with u but my doubt have when VSL link is goes down then both switch running on vss-dual-active-detection then both switch will be active Now my core VSS switch to edge switch non-stop communication will be continue untill my core VSS switch is not goes off or ? ? ?

Well, to quote Cisco " Any disruption or failure to communicate on the VSL link leads to a catastrophic instability in VSS."

Do you really want to try to identify what might still work?  Further, what might still work, might change between different IOS versions.

Basically, losing communication between the VSS pair, when both remain active is a "bad thing" (laugh); much, again, like a 3K stack that gets partitioned.

Don't misunderstand, I think it's fine to be curious about what might or might not work, but I hope your not planning on using anything you might discover in a production situation.

Anyway Thanks firend..

but basic my moto is if i give commitment in VSS mode nonstop communication will be 24/7/365 day then i need to know every single point of failure. and i have a upcomming a new project where i'm goint to test when our VSL link lose then what will be happend..

thanks a lot

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