[c-nsp] 6500 VSS for campus L3 core?

Andy Ellsworth andy at dar.net
Wed Feb 13 11:55:00 EST 2013

For those of you running 6500 VSS and using the traditional 3-layer campus
model (core/distro/access) with a layer 3 core...do you use VSS in your

We are using VSS in the core and distro layers today, but the more
$WEIRD_THINGS software bugs we encounter that affect the whole VSS pair on
our distros, the less inclined I am to keep VSS in the core.

My thinking is that at the distro layer, you at least get some significant
benefits for your layer 2 downlinks to your access switches (MEC, no STP,
no FHRPs). But in the core, where all of your connectivity is
point-to-point L3 links to distros, we can get all of those same benefits
with EC + ECMP OSPF (and we don't have anything hitting the core that would
need FHRPs).

The conclusion I've come to is that VSS at the distro layer has significant
benefits with some downsides, while VSS for a L3 core has very few benefits
but increased risk of software/human error failures.

Has anyone else gone through this thought exercise?


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