[c-nsp] BGP annoucements/iBGP

[Oliver Boehmer (oboehmer)]

Nick Kraal <> wrote on Thursday, March 15, 2007 2:41 PM:

> Hello all,
> 
> We have a set up simplified as this:
> 
> Internet---[eBGP]---BR---[iBGP]---AR---[eBGP]---Cust_A
> 
> On the AR, we are receiving 2 routing paths to the customer's prefix:
> [1] via Internet; 3 AS hops away
> [2] announced from directly connected customer to AR; prefix is
>      prepended 7ASNs
> 
> Now as I understand it AR will not announce the unattractive prepended
> prefix to the other local iBGP speakers in the network. And ultimately
> not announce this block to the Internet.
> 
> Is there a way to circumvent this? The customer wants to 'see' us
> announce the prepended announcement (although we have told them it
> will be announced if the more attractive one is removed).

No. Any BGP speaker will only announce one (the best) path. Your
customer needs to make his primary Internet connection even less
attractive (or shut it down) in order to test the backup and see you
announce his path.

	oli