[Xorp-hackers] OSPF problem with keep-alive messages.

[Atanu Ghosh]

Hi,

For a router to be fully adjacent with another router it must see hello
packets from its neighbour. The hello packet contains a list of the
neighbours that a router has seen, it is a requirement that a router
sees itself when receiving a hello packet to remain fully
adjacent. Using a Link State Update to maintain an adjacency would break
the protcol, it may cause one router to believe that it is fully
adjacent when it isn't.

Assuming that all 30 nodes are on the same subnet and the link-type is
"broadcast" I don't think that the hello messages should be crowded out,
if they are this is a problem.

When the router (10.2.3.3) was restarted it should have have identified
the DR and BDR and formed full adjacencies with only those two. The
number of routers shouldn't make much difference apart from the
background hello messages every 10 (default value) seconds from each
router.

	   Atanu.

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

    Ben> I notice something weird in my 30-node setup.

    Ben> 28 of my routers are up and functioning and in 'FULL' state.
    Ben> One had to be restarted because it had port conflicts with
    Ben> another.  Now, the restarted one is not able to sync with it's
    Ben> peers.  It seems to me that the problem is that during
    Ben> 'Loading' state, there is too much traffic and it crowds out
    Ben> the hello messages (I am running this over an emulated lower
    Ben> bandwidth and high latency link.)

    Ben> Should we consider an LS Update to be as good as a Hello message
    Ben> when trying to determine the 'Alive' status of a neighbor?

    Ben> Here is a snippet of a tshark dump for one of the interfaces on
    Ben> this router:

    Ben> 0.090164     10.2.3.2 -> 224.0.0.5    OSPF LS Update
    Ben> 0.090211     10.2.3.2 -> 224.0.0.5    OSPF LS Update
    Ben> 0.090261     10.2.3.2 -> 224.0.0.5    OSPF LS Update
    Ben> 0.100697     10.2.3.3 -> 10.2.3.2     OSPF LS Acknowledge
    Ben> 0.109600     10.2.3.3 -> 224.0.0.5    OSPF LS Update
    Ben> 0.136957     10.2.3.3 -> 224.0.0.5    OSPF LS Update
    Ben> 0.140972     10.2.3.3 -> 224.0.0.5    OSPF LS Update
    Ben> 0.143208     10.2.3.3 -> 224.0.0.5    OSPF LS Update
    Ben> 0.179049     10.2.3.3 -> 224.0.0.5    OSPF LS Update
    Ben> 0.182767     10.2.3.3 -> 224.0.0.5    OSPF LS Update
    Ben> 0.216704     10.2.3.3 -> 224.0.0.5    OSPF LS Update
    Ben> 0.229887     10.2.3.2 -> 224.0.0.5    OSPF LS Acknowledge
    Ben> 0.229942     10.2.3.2 -> 224.0.0.5    OSPF LS Update
    Ben> 0.229992     10.2.3.2 -> 224.0.0.5    OSPF LS Update
    Ben> 0.230042     10.2.3.2 -> 224.0.0.5    OSPF LS Update
    Ben> 0.230087     10.2.3.2 -> 224.0.0.5    OSPF LS Update
    Ben> 0.230132     10.2.3.2 -> 224.0.0.5    OSPF LS Acknowledge
    Ben> 0.230175     10.2.3.2 -> 10.2.3.3     OSPF LS Acknowledge
    Ben> 0.230223     10.2.3.2 -> 224.0.0.5    OSPF LS Update
    Ben> 0.230269     10.2.3.2 -> 224.0.0.5    OSPF LS Update

    Ben> Thanks,
    Ben> Ben

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

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