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Re: [eng/rtg][vendor specific] changing loopbacks
- From: Warren Kumari
- Date: Thu Sep 29 16:08:19 2005
So, on vendor C boxes you might be able to get away from having to do
a full reboot to change your OSPF ID by doing a "clear ip ospf process".
If you don't do this, even though you change the loopback address,
your router will still keep the old address as the OSPF router ID.
You won't actually end up with a route to the old loopback, but it
will still be in the OSPF database.
While this is less than optimal, it will still work (note, I don't
recommend running your network like this!). It is somewhat
disconcerting if you don't know that changing loopback address
doesn't automatically change OSPF ID and look in your OSPF
database and see addresses that you shouldn't / you retired, etc,
especially because most people only page through their OSPF database
when they suspect something is odd...
 As with most things, I am sure that the exact behavior depends
upon hardware and software version, phase of moon, flavor of
 Sure it seem obvious when you thin about it, but most people
don't seem to think.
On Sep 29, 2005, at 12:20 PM, Neil J. McRae wrote:
this is my fear. which is why i asked. pushing out new
configs (the canonic config is on disk, not the router )
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>.
I think with OSPF this will be very difficult to
do without rebooting (or as long an outage as rebooting).
We migrated from OSPF to IS-IS and changed some loopbacks a
while ago, the IS-IS change was totally transparent - no issue,
but on the change of loopback caused a lot of BGP churn.
It was easier to change it and reboot and do
it over a period of time in small network triangles.
I always thought that the billing system was the database
of record ;-)