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'.