[eng/rtg] changing loopbacks

Fri Sep 30 01:36:35 UTC 2005

On Fri, Sep 30, 2005 at 12:14:46AM +0100, Ian Dickinson wrote:
> 
> Randy Bush wrote:
> >>Personally, the cleanest way I've been able to accomplish changing this 
> >>in regard to OSPF, logging and authentication on Cisco's is to suck 
> >>down the running config, make the changes in your editor of choice, 
> >>push it back up to startup-config and schedule a reboot.  iBGP is much 
> >>easier to make the changes as you outline.
> > 
> > 
> > this is my fear.  which is why i asked.  pushing out new configs
> > (the canonic config is on disk, not the router [0]) and setting a
> > reload of a bunch of routers at time t0 does not give me warm
> > fuzzies about what the world will be like at time tn (n > 0).
> > 
> > but i may have to take that path.  i am hoping folk will give me a
> > magic pill.  after all, any group with such a deep understanding of
> > how to deal with the world's social ills must know a bit of router
> > magic <smirk>.
> 
> You may need to change your BGP router-id to match if you set it explicitly,
> which *may* alter path selection (a long way down the tree I admit).
> 
> Another nasty is if you run TE and use the old Loopback as your TE-ID,
> even with IS-IS.
> 
> Plus of course, your zone/hosts file for managing/polling these nodes in the
> first place :-)
> -- 
> Ian Dickinson
> Development Engineer
> PIPEX
> ian.dickinson at pipex.net
> http://www.pipex.net
> 
> This e-mail is subject to: http://www.pipex.net/disclaimer.html

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.

IS-IS and OSPF should be able to pick up the change as soon as the IP
address is entered into the config.

---
Wayne Bouchard
web at typo.org
Network Dude
http://www.typo.org/~web/