Comments on: Short and Sweet Cisco VSS

By: Phil

Phil — Tue, 19 Jan 2016 18:32:58 +0000

In reply to Marvin.

Yes especially with dual active detection but I wanted to get a very basic copy paste posted. You’re right though there is more you can build in especially if they’re not L2 only MDF switches or something

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By: Marvin

Marvin — Tue, 19 Jan 2016 18:11:09 +0000

Phil – no VSS keepalive link for you?

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By: Phil

Phil — Tue, 19 Jan 2016 18:05:05 +0000

In reply to SDNgeek.

I’ve used VSS mainly in building MDFs where 10gig ports were needed and rack space was at a premium or non existent. For that sort of deployment I’ve never had any issues, though I absolutely understand the philosophical discomfort with sharing a control plane.

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By: SDNgeek

SDNgeek — Tue, 19 Jan 2016 17:48:32 +0000

In reply to Ethan Banks.

We looked at VSS very closely for a while and it turns out that the philosophical issue with shared control plane works out in practice from what we saw. I very much dislike switch stack technologies as well which we do run in production and have caused a litany of operational nightmares. On the other hand we have run vPC for quite a while without any major issues.

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By: Phil

Phil — Tue, 19 Jan 2016 14:38:49 +0000

In reply to Ethan Banks.

Ah the classic tube and wing design. I’m still waiting for my shuttle craft.

I agree that VSS has limitations especially because it’s normally used in a campus core which is why I like the idea of a deconstructed core (campus not data center) and use good design and routing for fault tolerance. Cost is high, but if I had my druthers….I’ve also had VSS save my butt so I admit that there’s a soft spot in my heart for it too.

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By: Ethan Banks

Ethan Banks — Tue, 19 Jan 2016 14:34:06 +0000

There’s a philosophical discussion to be had about whether a shared control plane in the core is a good idea. I know that’s part of the VSS value proposition. And when it works, it’s a wonderful thing. But my brain always goes back to “shared fate,” and my anxiety kicks up.

I have never run VSS in anger, so this is partially my ignorance talking. I think I sense a blog or newsletter post coming, though. Something about compare/contrast the shared-fate risk of SDN-driven centralized control planes vs. VSS vs. stacks vs. separated control planes sharing common VLANs, routing protocols, etc.

All of these scenarios seem nominally fragile. The question in my mind then…which is least fragile.

And now I’m rambling. See you tonight, if my plane makes it to SFO. 2 hour delay so far. Whee! Shiny metal tubes are fun.

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