[j-nsp] iBGP impacting eBGP

[Scott Morris]

If your router was learning about that prefix via iBGP, then it would
disappear as soon as you kill the iBGP session.

If you don't have it in the table, it's kinda hard to announce it to
external peers!  

Check your BGP table (and routing table?) for whatever route you are no
longer announcing.

HTH,

Scott 

-----Original Message-----
From: juniper-nsp-bounces at puck.nether.net
[mailto:juniper-nsp-bounces at puck.nether.net] On Behalf Of Jad KAROUT
Sent: Monday, November 05, 2007 11:08 AM
To: juniper-nsp at puck.nether.net
Subject: [j-nsp] iBGP impacting eBGP

I'm encountering a problematic issue on our juniper M7i.

We use this router to announce our prefix to the world via two carriers (ts
and c&w). This router also establishes an iBGP link with another one of our
routers.

So the BGP configuration goes something like this :

jad at JUNIPER-BGP> show configuration protocols bgp

traceoptions {
     file bgp.log size 1m files 5;
     flag normal;
     flag state;
}
log-updown;
group T-S {
     type external;
     authentication-key "$9$wrsoGUjkf5Q-dXtc.f5yreKx-oJDi.5lKjk"; ##
SECRET-DATA
     export PREFIX_OUT;
     neighbor IP_TS {
         peer-as TS_AS;
     }
}

group XTS {
     type internal;
     local-address IP_J;
     neighbor IP_RB {
         export DONT_ADVERTISE;
     }
}

group CW {
     type external;
     authentication-key "$8*xtdpHKJHJKL-.hjkGUreKx-oJDi.ppWJoi"; ##
SECRET-DATA
     export PREFIX_OUT;
     neighbor IP_CW {
         peer-as CW_AS;
     }
}


However due to changes in our architecture, the iBGP session is no longer
needed and must be removed. I tried to do that by deleting the corresponding
group in the BGP conf as it is now useless.
However, the second i commit that change, the M7i stops announcing our
prefix to the two eBGP peers.

I don't understand how removing an iBGP session can impact eBGP sessions ?

Any idea anyone ?

Thanks.
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