[eng/rtg] changing loopbacks

Fri Sep 30 01:44:08 UTC 2005

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'.