[115577] in North American Network Operators' Group
Re: less than a /24 & BGP tricks
daemon@ATHENA.MIT.EDU (Stephen Kratzer)
Tue Jun 30 13:09:19 2009
From: Stephen Kratzer <kratzers@pa.net>
To: nanog@nanog.org
Date: Tue, 30 Jun 2009 13:08:53 -0400
In-Reply-To: <9515c62d0906300654n229ae622i4019b5bb45526c7f@mail.gmail.com>
Reply-To: kratzers@pa.net
Errors-To: nanog-bounces+nanog.discuss=bloom-picayune.mit.edu@nanog.org
Neal,
If your providers are doing uRPF, and it is always the case that hosts usin=
g=20
provider A's IPs must route through provider A, and hosts using provider B'=
s=20
IPs must route through provider B, then why not enforce this behavior in yo=
ur=20
routing tables rather than doing PBR?
=46rom your description, it doesn't sound like you're distributing subnets=
=20
across datacenters, and it's difficult to tell how, why, or if you're shari=
ng=20
provider routes between your routers.
Stephen Kratzer
Network Engineer
CTI Networks, Inc.
On Tuesday 30 June 2009 09:54:29 neal rauhauser 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.
>
> A while ago we got a /28 from each provider and attached it to a
> dedicated fast ethernet interface at each location. Inbound traffic arriv=
es
> normally and anything arriving on that port is policy routed to the
> upstream that provided the prefix.
>
> This was all well and good when it was a little firewall with a Linux
> machine behind it being used to check latency and do other diagnostics,
> but the sales people noticed it and have lined up a couple of opportuniti=
es
> to sell a service that would depend on our being able to receive and send
> traffic from blocks less than a /24.
>
> The policy routing works fine at low volume, but the RSP4 is rated to
> only do four megabits and I know they're going to exceed that.
>
> I can terminate this subnet on another router, wire that device into t=
he
> 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.
