North American Network Operators Group

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eBGP, iBGP, injecting networks

  • From: isaac
  • Date: Fri Feb 20 17:44:23 2004

greetings list,

hoping someone can hook me up on the right way to do this.    


we have two ASN's we control.

we have two border/edge routers (1 in each ASN) that talks to a
different backbone provider.

the two border routers peer with eachother over eBGP and also are in
the same OSPF process.  (we are working to merge them into the same

my question is this:

how do we achieve router redundancy between these two routers?

currently if we lose a transit link, the traffic will flow fine out
the other pipe.

but we don't have BGP network statements in router 2 that exist in
router 1 and we don't have BGP network statements in router 1 that
exist in router 2.

so the routes injected into BGP from router 1 will get withdrawn right
if router 1 dies?

is it a problem to announce the same networks from two different eBGP
peers to two different upstreams?


if you are still reading, thanks!

to clearify some more-

current setup:

current setup:

ASN 1 (we're not Genu!ty- just using for an example)


ASN 1 injects all of its own space and announces this space to and ASN 2

ASN 2 injects all of its own space and announces this space to Savvis
and ASN 1.

so stuff out on the net looks like:

1 6461 etc etc


1 2 6347


2 6347 etc etc


2 1 6461 etc etc


so, you see we are prepending on of our AS's on the way out.

the problem is tho, we only have 1 router in each respective Autonmous
System injecting address space.  if we lose that router, we lose
announcing that ASN's space.

is it totally going to cause probs to have routes originating from two
different AS's?  routing loops would be a real drag.

what about having an iBGP router in AS 1 inject the same space as the
border router in AS 1?  this other router also peers with AS 2....

thanks a lot!