[c-nsp] Dual-homing without BGP

Oliver Boehmer (oboehmer) oboehmer at cisco.com
Thu Feb 16 10:14:32 EST 2006

Vincent De Keyzer <> wrote on Thursday, February 16, 2006 3:55 PM:

> Hello,
> can you please review the following suggestion ?
> Requirements:
> *         Customer is a communications agency (i.e. more "content"
> than "access").
> *         They are doing serious things like e-commerce on the
> Internet connection they have with provider T (like 'trusted'). It's
> a 2M line. 
> *         They have a /23 which is announced as such on the global BGP
> network by provider T (although it's part of one of T's /16s)
> *         They are considering to buy a second Internet link at 25
> Mbps from provider N (like 'new'), on which they plan to do less
> serious things like video streaming.
> *         They also want to have some redundancy: if T link goes down,
> traffic goes out via N - but if N goes down, they don't want
> streaming to clog the limited T bandwidth, so no streaming in that
> case. 

So basically you want that all the streaming traffic will take the "N"
path, and if it's down, you drop the traffic so it doesn't clog T. Fine.
Then you basically want to ignore any dynamic routing information and
statically (via PBR) send the traffic to the "N" router. On the "N"
router, you statically PBR it to the "N" interface, and don't care if it
is up or down..
To suggest how to do this, we need a network topology, but essentially
you need to do PBR on every hop between the streaming server... make
sure to use "set interface Serialx/y Null0" on the "N" router to drop
the packets in case Serialx/y is down..

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