ECMP/multipath support

[Joakim Tjernlund]

Ondrej Zajicek <santiago at crfreenet.org> wrote on 2010/12/21 00:59:18:
>
> 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.

Not this one.
>
> 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).

yes, this one. Seems like multihop only works for ptp links then ?
perhaps not a big deal? I would think users of ECMP would like this case
to work too though.

 Jocke