From: john matijevic (matijevi@bellsouth.net)
Date: Sat Aug 07 2004 - 21:56:48 GMT-3
Also, I would like to add the reason they recommend between IBGP peers
is because typically you had more than one path between IBGP peers and
the EBGP peer was usually to an ISP that had only one path.
Sincerely,
John Matijevic, CCIE #13254, MCSE, CNE, CCEA
Network Consultant
Hablo Espanol
305-321-6232
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
john matijevic
Sent: Saturday, August 07, 2004 8:53 PM
To: 'Larry Metzger'; 'Group Study'
Subject: RE: BGP Update Source
Hello Larry,
Well I really don't recommend any best practices as far as the CCIE lab
goes. But I recall reading in either Doyle vol2 or Halibi, that the
update source, was used to establish IBGP relations between peers,
because of the redundancy, again you don't have to, it was just
recommended in the books. With EBGP peers it was not recommended. I
think that basically you should get that it's an alternative method of
establishing a bgp peer relationship, and "can" provide redundancy. I
hope that helps clarify some. :)
John Matijevic, CCIE #13254, MCSE, CNE, CCEA
Network Consultant
Hablo Espanol
305-321-6232
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Larry Metzger
Sent: Saturday, August 07, 2004 8:45 PM
To: 'Group Study'
Subject: RE: BGP Update Source
So....if we only have one path the update source really would not make
any difference. We include it as a best practice so we don't forget to
add it when we have redundancy.
Larry
-----Original Message-----
From: john matijevic [mailto:matijevi@bellsouth.net]
Sent: Saturday, August 07, 2004 5:37 PM
To: 'Larry Metzger'; 'Group Study'
Subject: RE: BGP Update Source
Hello Larry,
It sure does, try and setup a peering with using the physical interface,
than shut that interface down you will loose the adjacency. If you have
more than one path, to the destination and you peer with the loopback,
if you lose one link say your serial interface goes down, then the
adjaceny will remain assuming you have another route to the destination
say you had also an Ethernet to the same peer. I highly recommend
testing for yourself.
Sincerely,
John Matijevic, CCIE #13254, MCSE, CNE, CCEA
Network Consultant
Hablo Espanol
305-321-6232
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Larry Metzger
Sent: Saturday, August 07, 2004 8:34 PM
To: 'Group Study'
Subject: RE: BGP Update Source
Thanks for the input. I have seen the explanation, however I don't see
it make any difference in the configuration. With or Without it works!
Maybe it has to do with the redundancy mentioned.
Larry
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
john matijevic
Sent: Saturday, August 07, 2004 5:24 PM
To: 'Larry Metzger'; 'Group Study'
Subject: RE: BGP Update Source
Hello Larry,
The update source is necessary depending on what you are trying to
accomplish. From the doccd:
"neighbor update-source
To have the Cisco IOS software allow BGP sessions to use any operational
interface for TCP connections, use the neighbor update-source command in
router configuration mode. To restore the interface assignment to the
closest interface, which is called the best local address, use the no
form of this command. "
Also it looks like this command will be necessary when using ipv6 in the
future.
" The neighbor update-source command must be used to enable IPv6
link-local peering for internal or external BGP sessions."
This command also provides redundancy when peering between neighbors, so
that if one link were to go down, if another one was available, it would
still remain adjacent.
Sincerely,
John Matijevic, CCIE #13254, MCSE, CNE, CCEA
Network Consultant
Hablo Espanol
305-321-6232
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Larry Metzger
Sent: Saturday, August 07, 2004 8:10 PM
To: Group Study
Subject: BGP Update Source
I am working on BGP configurations. I have Router1 (as100) and Router2
(as200). I'm using the loopback on Router1 for the neighbor statement.
The recommendation is to add "neigh R2 update-source loop0" I have
configured these routers with and without the update source and
everything works fine either way (sh ip bgp, sh ip bgp nei, sh tcp). Is
it necessary? What problems will it cause if you don't change the
update-source?
Larry
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