[c-nsp] VSS or not for edge routing?

[Matthias Müller]

Hi,

On Tue, 3 May 2011 15:02:11 +0000
Mattias Niklasson <mattias.niklasson at deltamanagement.se> wrote:
> To be honest, I feel more on top of things using all the abbreviations above, but it would be really nice to get rid of STP. :) I have not seen any configuration examples where VSS is used in combination with BGP though. Anyone here that are doing this?

I've got some VSS systems running BGP, OSPFv2 and IS-IS. And in the Cisco whitepapers there are some hints doing dynamic routing with VSS (configuration notes and convergence times).

 
> What are your experiences when it comes to VSS stability and maintainability (failovers (SSO), software upgrades (eFSU), adding line cards and such)? Can I trust it? Any opinions are welcome.

To do BGP or any other dynamic routing protocoll you have to make sure, that gracefull restart is enabled, tested and working. This has to be configured on all participating routers. If gracefull restart isn't configured or not working, you'll lose all routing during a SSO.
SSO, eFSU and adding line cards worked quiet nice so far, but the major drawback of VSS is the single controlplane. So one bug/hardware error can take down your whole system. And an CPU overload on your VSS can take down your BGP sessions. Our L2 only VSS systems encountered only bug so far (doing a chassis upgrade), but on L3 we had more outages.
To be safe, I wouldn't recommend VSS for doing L3 stuff and even for L2 to get rid of STP I'd look for solutions that work without a single control plane (for example Nexus 5k/7k with VPC).

Bye,
Matthias