[c-nsp] BGP Route Nailing & Reoriginating

[Lawrence Wong]

Thanks Sergio, but the ASes are all "public". While AS1 can be "private" since it only connects to AS3 (aka the Internet) via R2/AS2, it is kept as public (and on BGP) to maintain compatibility for future growth. You are correct that traffic will be blackholed if the link between R1/R2 goes down but as the link is the only path out, it is still okay at this point. The idea is to reduce problem caused by link flapping and also to keep routing decision simple by not exposing another AS to AS3.


----- Original Message ----
From: Sergio D. <sdanelli at gmail.com>
To: lawrencewong72 at yahoo.com; cisco-nsp at puck.nether.net
Sent: Wednesday, December 6, 2006 1:00:37 AM
Subject: BGP Route Nailing & Reoriginating

You can if R1 is a private AS, you can then remove private on R2 before advertising to R3, AFAIK you can't "delete" a public AS. In regards to your second question, you can create an aggregate or static route pointing to Null on R2 and always advertise that to R3, but not sure why you wouldn't withdraw the routes if R1 to R2 go down, since you will be black holing traffic. 


Dear gurus,

I have an environment as follows:

       (R1 / AS1) <-> (R2 / AS2) <-> (R3 / AS3)


R1 (router 1) has AS number 1 (AS 1) and advertises the routes 1.1.1.0/24 and 2.2.2.0/24 to R2 which inturn advertises to R3. All advertisement is done via eBGP.

Is it possible to configure R2 such that the routes 1.1.1.0/24 and 2.2.2.0/24 are advertised to R3 under AS2 instead of AS1? At the same time, can R2 "nail" down the routes so that in the event the (physical & BGP) link between R1 and R2 is down, the route continues to be advertised to R3 (and under AS2)?

The objective is to "hide" AS1 and also to prevent BGP dampening at R3 caused by flapping link between R1 & R2.


TIA!

-- 
Sergio Danellli
JNCIE #170


 
____________________________________________________________________________________
Cheap talk?
Check out Yahoo! Messenger's low PC-to-Phone call rates.
http://voice.yahoo.com