less than a /24 & BGP tricks

Anton Kapela tkapela at gmail.com
Tue Jun 30 17:14:49 UTC 2009

On Tue, Jun 30, 2009 at 9:54 AM, neal rauhauser<nrauhauser at gmail.com> wrote:
>   I have a network with two upstreams that land in datacenters many miles
> apart. The hardware involved is Cisco 7507s with RSP4s and VIP4-80. I've got
> a curious problem which I hope others here have faced.
>   I can terminate this subnet on another router, wire that device into the
> 7507 with a crossover, and establish a BGP session. I'm wondering if there
> is a tidy way to set next hop in some fashion using route-maps such that all
> the marking would be done on the auxillary machine and the traffic passing
> through the 7507 would be CEF switched rather than process switched.

I hope the NANOG list can forgive me replying--I have a soft spot for 7500's.

A few things to check on your box before giving up:

-if you don't need v6 or mpls, run the most recent 12.0S code
available - cef-switched policy based routing (which I'm not convinced
is required to do what you describe) has been part of 12.0 feature set
since its inception. Weather it works or not due to regressions is
another story.


-12.4 main works well enough, adds mpls p/pe and ipv6 in cef

-"ip cef distributed" (make sure it's enabled, regardless of the IOS version)

Another suggestion is to place customers into their own unique
interface (i.e. sub-interface vlan, etc), and simply bind this
customer to a VRF corresponding to the provider they expect/wish/etc
to egress.


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