RE: Cisco access list - multihomed question

["Barry Raveendran Greene" <bgreene at cisco.com>]

Hello Brian,

Rephrasing - you want packets with a source address x.y.z.0/25 to bypass the
forward table (FIB) and be forwarded in a direction of you choice.

So what you are looking for is a "FIB bypass" feature. On the Cisco (where
is was first created) it is called Policy Based Routing (PBR).

There is a lab on PBR in the ISP Workshop materials
(http://www.cisco.com/public/cons/workshops/) and found via key word
searching on Cisco's web site. Note that in the middle of 12.0 we made PBR a
CEF feature - allowing it to handle more PPS and not be process switched. So
check the documentation for any specific details.

Also note that this will only take care of traffic being forwarded upstream
to the provider. It will not handle downstream traffic. For downstream
flows, tweaking BGP advertisements would be you best option.

Barry

> -----Original Message-----
> From: owner-afnog at uol.co.ug [mailto:owner-afnog at uol.co.ug]On Behalf Of
> Brian Longwe
> Sent: Saturday, October 27, 2001 8:18 AM
> To: afnog at afnog.org
> Subject: Cisco access list - multihomed question
>
>
> Hi,
>
> The scenario.
>
> - Two upstream circuits on the same border router
> - I want to use one to carry (outgoing) traffic for certain
> customer networks only
> - I want to use the other as the standard default for all other
> customer traffic
>
>
>
>    Upst #1 s0/0     [---------]
> --------------------[         ]< Upst #1 should route traffic for
> x.y.z.0/25
>                     [         ]
> --------------------[         ]
>    Upst #2 s1/0:16  [---------]< Upst #2 should route traffic for
> all others
>
> - Both upstream connections go to the same provider
> - There is no BGP with upstream provider, only static defaults (until now)
>
> Instinctively I want to define route-maps to block traffic for #2
> from #1 and block traffic for #1 from #2 with a "next-hop"
> statement to redirect in each route-map.
>
> Is this the right logic? Anyone with similar experience who can give tips?
>
> Thanks,
>
> Brian Longwe
>
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