[c-nsp] BGP route won't advertise

Pete Templin petelists at templin.org
Wed Mar 6 09:16:58 EST 2013


On 2/28/13 10:35 AM, Jerry Bacon wrote:

> It's complicated. I am doing transit for this customer, be we have
> common upstream peers, and I need to disallow his other advertisements.
> I'm sure there are better ways to do this, but my real problem is that I
> can't get one of my routers to advertise his routes, while the other one
> does.

Jon is right, deny or allow+tag is the way to go.

Simple example: "ASN" in this case is your ASN.  Make a cheat sheet like 
this: ASN:ABCDE.  The right side breaks out to:

A (route category) = 1 for customer, 2 for "yours", 3 for upstream
BC = pop number, set to 01 for now if you want a starting point.
DE = future expansion, set to 00 for now as a starting point.

This customer's routes would get tagged ASN:10100, your own aggregates 
would get tagged ASN:20100, and upstream routes would get tagged ASN:30100.

ip community-list 101 permit ASN:1....
ip community-list 102 permit ASN:2....
ip community-list 103 permit ASN:3....

route-map transit-out p 10
  match commu 101
route-map transit-out p 20
  match commu 102
route-map transit-out d 30
  match commu 103

Bingo, this prefix goes out, but other routes from that customer's AS 
(learned from one transit) don't flow to the other transit.

pt


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