On Aug 6, 2009, at 3:16 PM, Joakim Tjernlund wrote:
Acee Lindem <[email protected]> wrote on 06/08/2009 20:18:38:
Hello Joakim,
Hi Acee, I am back with my questions :)
On Aug 6, 2009, at 5:22 AM, Joakim Tjernlund wrote:
In "16.1.1. The next hop calculation" one have:
In the second case, the parent vertex is a network that
directly connects the calculating router to the
destination
router. The list of next hops is then determined by
examining the destination's router-LSA. For each
link in
the router-LSA that points back to the parent
network, the
link's Link Data field provides the IP address of a
next hop
router. The outgoing interface to use can then be
derived
from the next hop IP address (or it can be inherited
from
the parent network).
Suppose that one cannot find any links that points back, is it a
good
idea to treat this case as a intervening router:
If there is at least one intervening router in the
current
shortest path between the destination and the root, the
destination simply inherits the set of next hops from
the
parent.
That is, just inherit the next hops from its parents?
No - if the Router-LSA doesn't have a link to the Network-LSA you
don't use it in the SPF calculation. If fails the bi-directional
check.
The idea here is use some link until the remote end has updated its
LSA
to include the "back link" so the intervening router case will just
act as a substitute until next LSA update.
What I wonder is if this can cause more trouble than it solves, i.e
what
bad things can happen? Or won't it help at all?
I don't see that this achieves anything. If the router is reachable
through an intra-area path, the SPF will find it. You don't want to
do any second guessing - this will only create blackholes and routing
loops.
Thanks,
Acee
Jocke
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