[c-nsp] ISP / MPLS "POP" design

Mark Tinka mark.tinka at seacom.mu
Wed Oct 30 06:00:12 EDT 2013

On Wednesday, October 30, 2013 02:34:18 AM CiscoNSP List 

> I thought having RR's would negate the need to create a
> full mesh between PE's?    Initially there will be three
> POP's, but expect this to grow to 6+

Route reflectors are always a great idea, whether you have 
2x routers or 200x.

Setting it up from Day One makes life easier, as your 
network will always grow.

The only question is, do you deploy a route reflector on 
your core routers, or on different/dedicated devices?

> So you are suggesting that the "P" routers not be
> RR's(And not speak BGP, and only have MPLS+OSPF
> running?), and use the 2 7200's (With IPTransit
> connections) as the RR's?

Well, given the platform you're using as a core router 
(6500), if you used that as a route reflector, you would 
have to have the full BGP table on the devices, and we know 
how poorly this system is scaling, particularly in the FIB.

Secondly, the SUP720 (unless you have the SUP-2T) is not 
very quick. A route reflector, IMHO, needs to have some 
"oomph" to handle all its client, route churn, e.t.c. E-
mails abound on how the SUP720 is falling over when dealing 
with BGP and several sessions.

The BGP Selective Download feature would be very cool, where 
you don't download the BGP routes into the global RIB (and 
in so doing, you don't download them into the FIB), but I'm 
not sure whether this platform supports it (it is an IOS and 
IOS XE feature, but not sure whether the 6500 has it).

I would run dedicated route reflectors (even if they are 
cheap 7201's, for now), since your network is growing. This 
would also help keep BGP (not for IPv6 if you want native 
IPv6) out of your core, which is good. So it's not like it 
would be a poor investment. The 7200 does support BGP 
Selective Download, but you gains would be minimal here 
since the platform is CPU-based.

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