[Xorp-hackers] OSPF & migrating remote routers.

[Atanu Ghosh]

Hi,

>>>>> "Ben" == Ben Greear <greearb at candelatech.com> writes:

    Ben> The current implementation of OSPF, if the remote router-id
    Ben> changes, but the remote interface IP doesn't change, then OSPF
    Ben> doesn't notice that there is a new peer because it searches
    Ben> on the interface IPs instead of the router-id.

    Ben> With the patch below, it searches by router-id on broadcast
    Ben> interfaces too, and then it works in my case (I'm using
    Ben> ethernet-like interfaces.)

    Ben> What is the reason for searching by anything other than router-id,
    Ben> regardless of the interface type?

The specification RFC 2328:
----------------------------------------
	At this point, an attempt is made to match the source of the
	Hello Packet to one of the receiving interface's neighbors.  If
	the receiving interface connects to a broadcast, Point-to-
	MultiPoint or NBMA network the source is identified by the IP
	source address found in the Hello's IP header.	If the receiving
	interface connects to a point-to-point link or a virtual link,
	the source is identified by the Router ID found in the Hello's
	OSPF packet header.  The interface's current list of neighbors
	is contained in the interface's data structure.  If a matching
	neighbor structure cannot be found, (i.e., this is the first
	time the neighbor has been detected), one is created.  The
	initial state of a newly created neighbor is set to Down.
----------------------------------------

	Atanu.

    Ben> Thanks,
    Ben> Ben

    Ben> RCS file: /cvs/xorp/ospf/peer.cc,v
    Ben> retrieving revision 1.289
    Ben> diff -u -r1.289 peer.cc
    Ben> --- peer.cc     5 Oct 2007 00:06:59 -0000       1.289
    Ben> +++ peer.cc     5 Oct 2007 00:58:56 -0000
    Ben> @@ -1487,13 +1487,13 @@
    Ben>   {
    Ben>       typename list<Neighbour<A> *>::iterator n;
    Ben>       switch(get_linktype()) {
    Ben> -    case OspfTypes::BROADCAST:
    Ben>       case OspfTypes::NBMA:
    Ben>       case OspfTypes::PointToMultiPoint:
    Ben>          for(n = _neighbours.begin(); n != _neighbours.end(); n++)
    Ben>              if ((*n)->get_neighbour_address() == src)
    Ben>                  return *n;
    Ben>          break;
    Ben> +    case OspfTypes::BROADCAST:
    Ben>       case OspfTypes::VirtualLink:
    Ben>       case OspfTypes::PointToPoint:
    Ben>          for(n = _neighbours.begin(); n != _neighbours.end(); n++)

    Ben> -- 
    Ben> Ben Greear <greearb at candelatech.com>
    Ben> Candela Technologies Inc  http://www.candelatech.com

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