[c-nsp] BGP partial routes and partial carrier failures

[Bruce Pinsky]

On 10/3/2014 12:38 AM, Saku Ytti wrote:
> On (2014-10-02 12:29 -0700), Bruce Pinsky wrote:
> 
> Hi Bruce,
> 
>> How about not taking the default from them and set your own default based
>> on whatever criteria you chose.  You could, for instance, use Conditional
>> Advertisements to inject the default based on the presence or absence of
>> routing information from one or the other provider.  You could also use PfR
>> to select the outbound path based on availability/performance/cost.
> 
> You don't actually need anything this complex. Just recursing static route
> will do, and IOS by default recurses.
> So both upstreams would advertise to you some prefix they don't originate in
> the peer router, maybe their PA network from the core.
> 
> Then you'd have something like
> ip route 0.0.0.0 0.0.0.0 <pa-prefix>
> 
> If one upstream peer gets disconnected from their core, the PA-prefix is no
> longer sent via that peer, and it'll now recurse to the other provider.
> 

This can certainly work.  The good thing about conditional advertisements
is that they don't have to depend on just one prefix.  With the recurse
method, they do.

-- 
=========
bep