[Xorp-users] OSPFv2 P2P still uses 224.0.0.5
Atanu Ghosh
atanu at ICSI.Berkeley.EDU
Sun Apr 27 20:01:02 PDT 2008
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
Christian> _______________________________________________
Christian> Xorp-users mailing list
Christian> Xorp-users at xorp.org
Christian> http://mailman.ICSI.Berkeley.EDU/mailman/listinfo/xorp-users
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