[eng/rtg] changing loopbacks

Sun Oct 2 19:55:42 UTC 2005

--- Austin <amckinle at andrew.cmu.edu> wrote:

> 
> It's worth noting that C's don't need actual IP
> address space assigned to 
> the router-id for OSPF. It's just an arbitrary
> value; it's probably better 
> karma to set it to whatever you want (maybe
> something that doesn't look 
> like an IP address).
> 
> RFC 2328:
> 
>         Router ID
>             A 32-bit number assigned to each router
> running the OSPF
>             protocol.  This number uniquely
> identifies the router within
>             an Autonomous System.

eek!  There are a couple of downsides to having the
router-ID divorced from a physical address:

1) you get an additional number which you have to have
to track to ensure uniqueness.

2) you lose the benefit of being able to double check
reachability (ping/ssh to router ID)

3) RFC 1403 says that the BGP router identifier must
be the same as the OSPF router ID, and do you really
want your BGP to reflect an unreachable ID?

I've had a customer who used unreachable router IDs,
and it made their NOC work quite a bit harder than
they otherwise would have had to...

-David

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