[c-nsp] BGP Fast-external-fallover

[John Neiberger]

>> > If he would pass this flapping on, all/most/many
>> > peers/upstreams of him would have your prefix dampened, and
almost
>> > nothing he can do about it. You stay down until all their reuse
>> > timers expire.
>> 
>> But if you postulate an enterprise with N locations,
>> the other N-1 locations will find the location with
>> the flapping circuit completely unreachable, rather
>> than only partially unreachable.
>
>If you speak BGP, you are multihomed. You don't lose connectivity
>completely.
>

In my original post I mentioned that this is an MPLS-based VPN network,
not the Internet. We are not multihomed but we still require BGP for
dynamic routing advertisements to and from our VPN provider. Any
instability introduced by my routes flapping should only affect my VRF,
or routing instance, or whatever the heck you want to call it. :) 
Additionally, none of my sites advertises more than just a handful of
routes, perhaps ten at the most.

>> > Propagating the instability hurts more than damping
>> > it early at the source.
>> 
>> Dampening, like bogon filtering, is something which is
>> a good idea in theory, but in practice, can do far
>> more harm than good, unless it's very, very carefully
>> managed.  
>
>Of course. People doing BGP who don't know what they do usually do
more
>harm than good. And obviously there are still misconceptions about
>dampening out there.

Here's the real-world scenario that eventually led to my original
question: one of my sites was having circuit problems and once Qwest
local fixed the circuit, I was still down because of dampening and I had
to call Qwest to have them manually clear the dampening on those routes.
I don't want that to happen and I've already spoken with them about
removing dampening but I'm not making any headway. 

John
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