From: steven.j.nelson@xxxxxx
Date: Mon Apr 29 2002 - 14:37:59 GMT-3
Hi Pete
Well Well Well
I think we finally nailed it.
RFC 1403 (1993)
Originating router ID (OSPF Only) and BGP Router ID must match for
synchronisation to occur.
See the attached document.
Thanks
Steve
-----Original Message-----
From: Allison,R,Ray,IVNH25 ALLISOR C
Sent: 29 April 2002 18:17
To: Nelson,SJ,Steven,IVNH25 C
Subject: RE: BGP Synchro (Time to tear your hair out Pete)
Steve,
I've just tried it. Your mate is right on his first paragraph, the
router ID is definitely making a difference. I got the problem when I
started forcing router ids to non default values on BGP or OSPF. Changed
both my BGP and OSPF Router IDs to the same garbage value on my originating
router and everything is fine.
When I tried it and spoke to you the first time and said it worked for me,
my OSPF and BGP router IDs must have been the same, I cannot have checked
closely enough.
Anyway, having dug deeper. I have found a later version of BGP Bestpath
Algorithm (attached) than I have used previously.
Its there in black and white at the beginning. !! If the IGP route is an
OSPF one the Router IDs must match. This is the first time I have seen this.
However, not sure I agree with the second paragraph, reflection and
Synchronisation do work together.
cheers
ray
-----Original Message-----
From: Nelson,SJ,Steven,IVNH25 C
Sent: 29 April 2002 15:44
To: Allison,R,Ray,IVNH25 ALLISOR C
Subject: FW: BGP Synchro (Time to tear your hair out Pete)
Ray
This is Pete's response.
Haven't tried it yet...
-----Original Message-----
From: Peter van Oene [mailto:pvo@usermail.com]
Sent: 29 April 2002 14:55
To: Nelson,SJ,Steven,IVNH25 C
Subject: Re: BGP Synchro (Time to tear your hair out Pete)
Hi Steve,
I do hate this feature but I'm glad to offer what little insight I have.
In your question, I am assuming the BGP route is not best because it is not
synchronized. If this is the case, it is because the BGP RID of the
originating router does not happen to match the OSPF RID for the OSPF route
for the same prefix. I further think, though I haven't verified it, that
cisco actually compares the OSPF advertising router to configured BGP peer
address for the BGP neighbor that advertises the route in question. I
believe this because route reflection seems to break synchronization which
it shouldn't if the router actually compared the originating router in BGP
since that attribute would not change upon reflection. Anyway, I'm really
likely not making much sense here :)
Should answer is match your OSPF and BGP RIDs and if things don't work,
make sure you are peering to the same address that is also the OSPF RID (ie
peer to the highest configured loopback address) This should make things
happy. If there is reflection and synchronization, I don't think it can
work (this two technologies are not designed to work together).
Does that help at all?
Pete
At 01:19 PM 4/29/2002 +0100, steven.j.nelson@bt.com wrote:
>Pete
>
>I have many good answers to BGP questions from you that I have posted to
>groupstudy, so I thought I'd cut out the middle man and mail you direct. I
>hope you don't mind.
>
>There seems to be a lot of discussion on BGP Syncronisation when the bgp
>route is also present in the IGP table but not marked as best ">" and alot
>of answers seem to revolve around the Router Id's of the OSP (IGP) and the
>BGP (IBGP) routers.
>
>Can you point me in the right direction for the answer to this problem so
>that I can get it sorted, I have a scenario that you can take a look at if
>you wish, but I was just interested in the "Simple" if there is one,
answer.
>
>Many thanks Pete
>
>And keep up the good work in the group.
>
>all the best
>
>Steve
>
>Steve Nelson
>Customer Engineer
>BT Ignite- National Solutions
>T: +44 (0)1422 338881 M: +44 (0)7811 944172
>e-mail: steven.j.nelson@bt.com
>pp HW A170, PO Box 200(HOM-NZ), London, N18 1ZF
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