From: Fred Ingham (fingham@xxxxxxx)
Date: Mon Aug 19 2002 - 20:55:17 GMT-3
Claudine: Your observation re the next hop is correct. OSPF network type
NB or Broadcast will have the next hop as the originating router. OSPF
network type PTMP will have the next hop as the spoke router.
This can have an effect in some multicast scenarios as the RPF (reverse path
forwarding) taken from the routing table can point to the originating router
rather than the hub and multicast may not be configured over that link.
NB network type DOES require nei statements on the hub router. This is
because the hellos and LSA's are send unicast. Adjacencies will form
without the broadcast parameter on the frame maps. PTMP requires the
broadcast parameter on frame maps but does not require neighbor statements
as the hellos are sent via multicast.
As pointed out in other replies, no policy routing is required. I recommend
static maps on all physical and multipoint interfaces to avoid dynamic
mapping of undesired dlci's. In most test scenarios the dlci's are
configured as a full mesh but only certain dlci's are to be used.
HTH, Fred
----- Original Message -----
From: "Claudine DEMAR" <lkcnet00@hotmail.com>
To: <ccielab@groupstudy.com>
Sent: Saturday, August 17, 2002 11:10 AM
Subject: OSPF NBMA and policy routing
> Hello.
>
> Little Question regarding OSPF over NBMA networks:
> R1, R2, R3, R4 connected in a hub(R1)- spokes topology.
> R1 has a subint multipoint; R2, R3, R4 are configured on their physical
> serials. All routers in area0. R1 is DR.
>
> Finally, the difference between using NBMA and POINT_TO_MULTIPOINT would
be
> that in the first case(NBMA) the spokes will see the routes for the other
> router's networks with next-hop=remote router.
>
> In second case (PTMP), the spokes will see the routes for the other
router's
> networks with nexthop=hub router.
>
> Is that correct ???
>
> Also solutions to OSPF over NBMA would be to use frame map ip statements
or
> policy routing. Is that correct ?? Any other suggestions ?? Any reference
> books or papers on the subject ?
>
> Many thanks,
>
> Claudine
>
>
>
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