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RE: ospf router-id (error in doc) posted 01/08/2001
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IMHO, the following are the correct order of preference:

1) do what the lab instructions tell you

2) if the instructions do not specifically forbid it - use a loopback
addressing scheme that allows you to easily identify routers. Makes doing
and undoing virtual links a lot faster

all IP routers, in compliance with RFC1812, if nothing else, have a RID.
OSPF uses it specifically, and under a certain set of rules. But the RFC
specifies that every IP router have one. Other places where the RID is used
( but not seen in any show command I have found ) is with unnumbered links.
It is the neighbor RID that allows the two routers to function properly
without assigning addresses. I believe that EIGRP uses each link address as
the router RID. Show ip eigrp neighbor seems to indicate that. Or rather,
EIGRP does not use a unique router RID, but an identifier based on the
interface. It does not use the loopback that I can tell. Come to think of
it, I don't recall that 1812 specifically states that RIDs need be unique in
a domain, although 2328 (OSPF) does indeed specifically state that
requirement for OSPF routers.

Come to think of it, other than OSPF, anyone familiar with instances where a
systematic router RID is necessary?

Chuck

-----Original Message-----
From:	nobody@xxxxxxxxxxxxxx [mailto:nobody@xxxxxxxxxxxxxx] On Behalf Of
Chuck Church
Sent:	Monday, January 08, 2001 6:55 AM
To:	ccielab@xxxxxxxxxxxxxx
Subject:	RE: ospf router-id (error in doc)

All,

     I meant to post about this earlier.  In the lab, what would be better
to use, loopbacks or just the router-id?  In a production network, I'd lean
towards the loopback since it's pingable, but in the lab, I'd hate to lose
points because my loopback wasn't pingable or had created another host
route.  Any preference?

Chuck Church
CCNP, CCDP, MCNE, MCSE
Sr. Network Engineer
Magnacom Technologies
140 N. Rt. 303
Valley Cottage, NY 10989
845-267-4000 x218



-----Original Message-----
From: Brian Hescock [mailto:bhescock@xxxxxxxxx]
Sent: Monday, January 08, 2001 9:48 AM
To: ccielab@xxxxxxxxxxxxxx
Subject: ospf router-id (error in doc)


fyi:   documentation bug CSCdt12293 has been filed to correct univercd
so it doesn't say the ospf router-id command came out in 10.0.  They'll
verify what version it actually came out in (around 12.0(7)) and will
make the change.

Brian

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