[c-nsp] Dual-homing scenario

[Oliver Boehmer (oboehmer)]

david raistrick <> wrote on Thursday, February 22, 2007 4:38 PM:

> On Thu, 22 Feb 2007, Roy wrote:
> 
>> In all scenarios set a default route to ISP1 that is lower in
>> priority than the one to ISP2
> 
> Here's a question:
> 
> If you're receiving a default from ISP2 but can't get one from ISP1: 
> Can you set a static default that's lower priority than the received
> default? 

no. Even if you use a static default with an admin distance (AD) of 20
(i.e. the eBGP admin distance), IOS will install the static due to its
lower default AD. When two protocols try to install a route with the
same AD, IOS uses the protocol's default AD as a tie-braker to make
route installation predictable..

So you can only do multi-path if the prefix is installed by the same
protocol, i.e. you would need ISP1 to generate a default route to
load-share.

	oli