From: Devender Singh (devender.singh@xxxxxxxxxxxxxx)
Date: Wed Feb 07 2001 - 03:05:05 GMT-3
Devender Singh
BE(Hons), CCNP
IP Solution Specialist
-----Original Message-----
From: Devender Singh
Sent: Wednesday, 7 February 2001 4:56
To: 'Steven Weber'
Subject: RE: next hop self...
Hi Steve,
I wiil try to explain it to you.
Let's say we have 3 routers two in one as and one in another as follows:
R1(1.1.1.1)---ebgp----(1.1.1.2)-R2-(10.1.1.1)---ibgp----(10.1.1.2)R3
Say, no other routing protocol is running. Now R3 does not have 1.1.1.0 in
its routing table.
R2 receives update from R1. It puts it in its database and in routing table.
Then it sends those updates to R3. But bgp rules state that in ibgp updates
next hop address will not change by default. Hence R3 will have all these
route in its bpg database whose next hop is 1.1.1.1 . Again bgp rules state
that if next hop is unreachable route is not considered. So all the bgp
routes from R1 are not considered by R3.
Work around:
If you want the route to be considered. What you do is put next-hop-self on
R2 for R3. It will change the next hop to 10.1.1.1, which isokay as for as
R3 is concerned and then it will considered the routes.
I hope it makes sense to you.
Devender Singh
BE(Hons), CCNP
IP Solution Specialist
-----Original Message-----
From: Steven Weber [mailto:itweber@netzero.net]
Sent: Wednesday, 7 February 2001 3:03
To: ccielab@groupstudy.com
Subject: next hop self...
I know this is a silly question but I am having a hard time
understanding the function of the next hop self command. I read up on it
in Halabi and I'm still having problems. Anyone care to shed some light?
Thanks,
Steve
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