I need an opinion regarding design for our new VSS layer we are about to implement. The new VSS switches will be connected to our core (two core 7600 routers), looking over design suggestions from Cisco, it appears the best solution for HA connectivity would be to use MEC on the VSS switches (two MEC connections, one MEC group on one chassis going to both core routers and one MEC group on the other chassis going to both core routers). Now for the core routers, would we use an etherchannel group for these connections as well and assign them /30 addresses. OSPF would be configured to load balance across these two equal paths as well.
Does that sound like the best configuration in regards to HA or does someone have a better design idea?
Re: VSS Configuration Question Regarding MEC and OSPF
You say: one MEC group on one chassis going to both core routers and one MEC group on the other chassis going to both core routers. This is actually not correct. In VSS you can't create a MEC on one chassis and a MEC on the other chassis. There is no such thing as "one chassis and the other" in VSS.
You just create one portchannel in VSS and put two interfaces of seperate chassis in it for example gi1/1/1 (first chassis) and gi2/1/1 (second chassis)
Then on the routers you should create a portchannel using two interfaces.
This is the best.
i use lacp or pagp also on my portchannel. i experienced this to be -just- a little better than "mode on".
and second, if you are running ospf across the links, make sure you have NSF enabled and configured on all devices and don't configure the OSPF timers too quickly. i suggest not using sub-second timers, but just leaving them to default.
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