[Xorp-users] OSPFv2 P2P still uses 224.0.0.5

[Atanu Ghosh]

Hi.

The specification requires that the destination address for
point-to-point networks is 225.0.0.5.

RFC 2328 A.1 Encapsulation of OSPF packets
----------------------------------------
	AllSPFRouters
	    This multicast address has been assigned the value
	    224.0.0.5.	All routers running OSPF should be prepared to
	    receive packets sent to this address.  Hello packets are
	    always sent to this destination.  Also, certain OSPF
	    protocol packets are sent to this address during the
	    flooding procedure.
----------------------------------------

RFC 2328 8.1.  Sending protocol packets
----------------------------------------
	The IP destination address for the packet is selected as
	follows.  On physical point-to-point networks, the IP
	destination is always set to the address AllSPFRouters.  On all
	other network types (including virtual links), the majority of
	OSPF packets are sent as unicasts, i.e., sent directly to the
	other end of the adjacency.  In this case, the IP destination is
	just the Neighbor IP address associated with the other end of
	the adjacency (see Section 10).  The only packets not sent as
	unicasts are on broadcast networks; on these networks Hello
	packets are sent to the multicast destination AllSPFRouters, the
	Designated Router and its Backup send both Link State Update
	Packets and Link State Acknowledgment Packets to the multicast
	address AllSPFRouters, while all other routers send both their
	Link State Update and Link State Acknowledgment Packets to the
	multicast address AllDRouters.
----------------------------------------

        Atanu. 

>>>>> "Christian" == Christian Svensson <info at cmd.nu> writes:

    Christian> Hello.
    Christian> My configuration looks like this:

    Christian> area 0.0.0.3 {
    Christian> area-type: "normal"
    Christian> interface "eth0" {
    Christian> link-type: "p2p"
    Christian> vif "eth0" {
    Christian> address 10.254.0.1 {
    Christian> priority: 128
    Christian> hello-interval: 10
    Christian> router-dead-interval: 40
    Christian> interface-cost: 5
    Christian> retransmit-interval: 5
    Christian> transit-delay: 1
    Christian> passive: false
    Christian> neighbor 10.254.0.2 {
    Christian> router-id: 10.254.0.2
    Christian> }
    Christian> disable: false
    Christian> }
    Christian> }
    Christian> }
    Christian> }

    Christian> Looking at the packets that passes out of eth0, the only ones that
    Christian> seems to be OSPF-related are heading towards 224.0.0.5. My link
    Christian> between 10.254.0.1 and 10.254.0.2 strips some undocumented segments
    Christian> from packets and it does not handle multicast at all, thus I'm looking
    Christian> for a way of using unicast instead of multicast for inter-router
    Christian> communications. Looking at the OSPFv2 RFC and the P2P mode it appears
    Christian> that this is what I'm looking for but I could be wrong.

    Christian> Using Xorp 1.4.

    Christian> Greetings,
    Christian> --
    Christian> Christian Svensson
    Christian> Command Systems

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