From: Adel Abushaev (adel@netmasterclass.net)
Date: Mon Dec 08 2003 - 15:25:25 GMT-3
You may use "network x.x.x.x backdoor", or simply increase the distance for
EBGP route to higher value than
the IGP which is used for synchronization. In this case, EBGP will enter the
routing table when IGP disappears.
The drawback will be, however, if IGP route still present in routing table,
but IBGP peer relationship is dropped
for any reason. In this case, EBGP will not get installed.
Adel Abouchaev
CCIE# 12037, MCSE
http://www.netmasterclass.net
----- Original Message -----
From: <Ken.Farrington@barclayscapital.com>
To: <soup_ccie@hotmail.com>; <ccielab@groupstudy.com>
Sent: Monday, December 08, 2003 5:53 AM
Subject: RE: BGP-IGP and synchronization
> Hi There,
>
> This is a really good subject and one that does cause confustion.
>
> You are right, it can be the route that gets there first (YUK!)
>
> You will probably see something like "not sync" when you do a show IP BGP
> (prefix)
>
>
>
>
>
>
> -----Original Message-----
> From: Soup Shi [mailto:soup_ccie@hotmail.com]
> Sent: 08 December 2003 05:12
> To: ccielab@groupstudy.com
> Subject: BGP-IGP and synchronization
>
>
> Hi, group,
> I know it is an old topic and must be discussed over and over.
> However, I can not figure it out even I feel I understand it completely.
> Say a router learns a route from both IGP, EBGP and IBGP, the IBGP has a
> shorter as-path than EBGP. From my understanding, the IGP route would get
> into routing table finally, because IBGP and EBGP routes got compared
first
> in the BGP table and the IBGP wins, then it failed when compared with IGP
> route when going towards routing table since its bigger AD.
> However, when the synchronization is on. There is no guarantee at all! It
> depends on who comes first. If the EBGP route comes earlier than IGP, it
> gets into routing table first, so the IBGP is never valid in BGP table.
The
> result is IGP loses its competition since its bigger AD.
> Is there any ways to avoid this lottery picking? I think most of the time
in
>
> a lab, the only reason for redistribution between BGP and IGP is that we
are
>
> not allowed to turn off the synchronization. So do we have to rely on pure
> luck in a CCIE lab exam?
> Thanks in advance.
> Soup
>
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