[c-nsp] L3 Switch as a BGP Gateway

[Jeff Kell]

On 6/27/2011 2:59 PM, 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?  

They can't scale to a full BGP feed.  If you do some exaggerated
filtering and aggregation, maybe; if you just want defaults plus a few
key routes, sure.

I'm not sure about the Metro version of the 3750, but a few other data
points...

WS-3750G:

> #sho sdm prefer routing
>   number of unicast mac addresses:                  3K
>   number of IPv4 IGMP groups + multicast routes:    1K
>   number of IPv4 unicast routes:                    11K
>     number of directly-connected IPv4 hosts:        3K
>     number of indirect IPv4 routes:                 8K
>   number of IPv4 policy based routing aces:         0.5K
>   number of IPv4/MAC qos aces:                      0.5K
>   number of IPv4/MAC security aces:                 1K

WS-3750E and WS-3750X are the same exact values.  For that matter so are
the 3560G and 3560X. 

But oddly enough, I have a 3750G-12 stack that shows a bit more:

> #show sdm prefer routing
>   number of unicast mac addresses:                  6K
>   number of IPv4 IGMP groups + multicast routes:    1K
>   number of IPv4 unicast routes:                    20K
>     number of directly-connected IPv4 hosts:        6K
>     number of indirect IPv4 routes:                 14K
>   number of IPv4 policy based routing aces:         0.5K
>   number of IPv4/MAC qos aces:                      0.5K
>   number of IPv4/MAC security aces:                 1K

And an old 3550-12 (if you don't need the extended match template [IPv6
or VRFs or policy routing]):

> PCP-Phase-III-3550#sho sdm prefer routing
>
>  number of unicast mac addresses:   6K
>  number of igmp groups:             6K
>  number of qos aces:                1K
>  number of security aces:           1K
>  number of unicast routes:          24K
>  number of multicast routes:        6K

But bottom line, 24K is a whole lot less than the current routing tables
(~360K last I checked).

If you have a truckload of cash, and get the precisely correct
supervisors / blades / daughtercards, the 6500/7600 can do multihoming
with full feeds, but I think that's the only Catalyst platform that can.

Jeff
Jeff