ECMP/multipath support

[Ondrej Zajicek]

On Fri, Dec 17, 2010 at 02:36:50PM +0100, Joakim Tjernlund wrote:
> Question:
> 
> in calc_next_hop() does this* match
>  16.1.1 para 5. ...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...

..

> Should not OSPF add a nexthop for ALL links that point back:
> ...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).

Not sure what you exactly mean. For a common scenario when
there are two (or more) parallel links between two routers,
multihop is used, because calc_next_hop() is called each time
for each link and the results are merged.

Or if you means case like: Router A having two interfaces (with IP1 and
IP2)  connected to the same network N, router B also connected to
network N may use multihop to IP1 and IP2 for routes that goes through
router A. It is true that in that case BIRD does not use multihop (and
there are some other corner cases, where multihop also is not used
although it could be).

-- 
Elen sila lumenn' omentielvo

Ondrej 'SanTiago' Zajicek (email: santiago at crfreenet.org)
OpenPGP encrypted e-mails preferred (KeyID 0x11DEADC3, wwwkeys.pgp.net)
"To err is human -- to blame it on a computer is even more so."
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