Subject: Interaction of ICMPv6 Router Advertisement and OSPFv3

From: Mike Fox <[email-masked]>
Date: Thu, 3 Apr 2003 10:47:29 -0500

Just wanted to follow up on the thread I started earlier this week on how a
hybrid host/router would treat Router Advertisement routes.  I realize that
my initial query was not completely clear and we may have some terminology
and assumption mismatches, so here is the summary of the design that I have
tenatively adopted based on mailing list discussions and discussions with
some router people.

One thing that I may not have made clear in the previous thread that I was
only referring to the logic for an interface on which OSPFv3 is running.
In this case,  we have decided that all on-link prefixes for this interface
will be considered OSPF internal, whether learned via ICMPv6 Router
Advertisements or link-LSAs, or both.

Rationale: for link-LSAs the rationale is obvious -- it's an OSPF internal
advertisement after all.  If OSPFv3 is running on a link, a link-LSA should
be sent by a router for all on-link prefixes anyway, so the case in which
an ICMPv6 Router Advertisement is received for an on-link prefix but not a
link-LSA should be rare -- it should only happen when there is a router on
the link which is not running OSPFv3.  In that case, we decided that all
prefixes that are on-link to an OSPF link should still be considered OSPF
internal for a couple of reasons.  First, that's how we do it in IPv4. I
know it isn't exactly analogous, but the subnet of an IPv4 OSPF interface
is considered internal to OSPF.  Another reason is because a prefix learned
via ICMPv6 Router Advertisement may be used for stateless autconfiguration,
resulting in a home address for the interface.  All home addresses on an
OSPFv3 interface are  internal to the OSPFv3 automous system.  It didn't
seem to make sense to have a host address that is internal to the
autonomous system, but the prefix that it is part of is not.

As an aside, for interfaces on which OSPFv3 is NOT running, all home
addresses and on-link prefixes will be considered external to the OSPF
autnomous system, regardless of how they are learned.  Their importation
will be controlled by the "import direct routes" knob.

Mike

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From: Acee Lindem <[email-masked]>
Date: Thu, 3 Apr 2003 11:01:50 -0500

Mike,

Sounds like a reasonable host implementation.

--
Acee