[Xorp-users] OSPFv2 P2P still uses 224.0.0.5

Christian Svensson info at cmd.nu
Sun Apr 27 22:46:05 PDT 2008


Hi,

I see. I will look into using virtual links, maybe the solution for me
lies there.

Thanks!

On Mon, Apr 28, 2008 at 5:01 AM, Atanu Ghosh <atanu at icsi.berkeley.edu> wrote:
> 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
>



-- 
Christian Svensson
Command Systems



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