[84992] in North American Network Operators' Group
Re: [eng/rtg] changing loopbacks
daemon@ATHENA.MIT.EDU (Christopher L. Morrow)
Thu Sep 29 21:44:37 2005
Date: Fri, 30 Sep 2005 01:44:08 +0000 (GMT)
From: "Christopher L. Morrow" <christopher.morrow@mci.com>
In-reply-to: <20050930013634.GA55709@typo.org>
To: nanog@nanog.org
Errors-To: owner-nanog@merit.edu
On Thu, 29 Sep 2005, Wayne E. Bouchard wrote:
<chopped ian's good infos>
>
> Of course, you can always pre-deploy ibgp sessions and TE configs to
> the new address (which will remain down until the new address exists),
> go for your OOB access to the box, change the loopback IP address (and
> associated references), "clear ip bgp *" and accept the 2 minute
> interruption. Changing loopback IPs is difficult to do gracefully but
> can still be done relatively quickly.
The clearing MIGHT have a larger effect, especially depending on the
number of peers you have and this device's placement in your network. I'd
think that a graceful bgp switchover would be simple enough (and wouldn't
require clear ip bgp *) The devil, IMHO, is in the IGP switches :( (not
withstanding ian's noted bgp router-id change)
>
> IS-IS and OSPF should be able to pick up the change as soon as the IP
> address is entered into the config.
>
ospf doesn't, for router-id on cisco's atleast, as Warren pointed out :(
however! switching from ospf to 'another igp' (ISIS would work well) would
avoid that, slide off ospf and onto ISIS, kill ospf when all next-hops
switch, which should be 'as soon as isis converges'.
