[c-nsp] L3 Switch as a BGP Gateway

[Seth Mattinen]

On 6/27/2011 11:59, Jason Greenberg wrote:
> Can someone advise me as to why a 3750 L3 Switch (Metro Model) wouldn't outperform a 7300 series router as a multi-homed BGP gateway?  ISRs and Enterprise class routers are still quite a bit more expensive than the L3 Switches, but I'm starting to not understand why.   I understand that L3 switches are less feature rich on the routing end, but suppose that our ASAs are doing most of the complicated filtering.    I know it doesn't sound "right" to have a 3750G used in this manner, but I am having a hard time finding any real reason why not to do it.
> 

It will outperform a software router and move packets at line rate. It
doesn't even have to be the metro version. It will fail at:

1) Having enough TCAM/memory to take more than a handful of routes
2) Doing anything substantial in CPU (like BGP calculations)
3) Forwarding in CPU if the TCAM is exceeded

If you intend to only take a BGP default route and announce some
prefixes upstream it will likely do just fine. Plenty of people utilize
L3 switches in this role.

~Seth