Subject: Changing router ID in OSPFv3

From: Mike Fox <[email-masked]>
Date: Fri, 16 May 2003 11:13:51 -0400

The RFC for OSPFv2 in section 12.4.2 Network Links, describes this logic for
when a designated router changes router ID:

in those rare cases where a router's
Router ID has changed, any network links advertisements that
were originated with the router's previous Router ID must be
flushed. Since the router may have no idea what it's
previous Router ID might have been, these network links
advertisements are indicated by having their Link State ID
equal to one of the router's IP interface addresses and
their Advertising Router not equal to the router's current
Router ID (see Section 13.4 for more details).

Then section 13.4  Receiving self-originated link state, says:

A self-originated advertisement is detected when either ....
(2) the advertisement is a network links
advertisement and its Link State ID is equal to one of the
router's own IP interface addresses.

In RFC 2740 a self-originated advertisement is simplified to simply be one
whose LS originator matches your router ID.

So is there any equivalent function to the above in OSPFv3?  Since link
state IDs in network LSAs are now interface IDs which are very unlikely to
be unique, the above-described situation seems impossible to detect in
OSPFv3.  Therefore in OSPFv3 perhaps the only acceptable way to change
router ID is to flush all old adverts first?

Mike

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From: Acee Lindem <[email-masked]>
Date: Fri, 16 May 2003 11:32:00 -0400

Hi Mike,

> router ID is to flush all old adverts first?

No need to do this. As long as all the routers on the network correctly
identify the new DR in their router LSA links to the transit
network (type 2), the stale network LSA shouldn't be used. This is one
benefit of always identifying a router by it's router ID (in OSPFv2 it
is identified in the type 2 link by it's address on the transit network).

--
Acee