[Xorp-hackers] OSPF stuck in TwoWay state.
Atanu Ghosh
atanu at ICSI.Berkeley.EDU
Sat Oct 20 10:55:55 PDT 2007
Hi,
This behaviour is correct.
Interfaces of type broadcast and NBMA will elect a DR and BDR if there
are enough neighbours. In this case only the DR and BDR need to form
full adjacencies with all neighbours, the other neighbours will stay in
the 2-Way (TwoWay) state.
---------------------------------------- RFC 2328 Section 10.4
10.4. Whether to become adjacent
Adjacencies are established with some subset of the router's
neighbors. Routers connected by point-to-point networks,
Point-to-MultiPoint networks and virtual links always become
adjacent. On broadcast and NBMA networks, all routers become
adjacent to both the Designated Router and the Backup Designated
Router.
The adjacency-forming decision occurs in two places in the
neighbor state machine. First, when bidirectional communication
is initially established with the neighbor, and secondly, when
the identity of the attached network's (Backup) Designated
Router changes. If the decision is made to not attempt an
adjacency, the state of the neighbor communication stops at 2-
Way.
...
----------------------------------------
Atanu.
>>>>> "Ben" == Ben Greear <greearb at candelatech.com> writes:
Ben> Is it ever valid for neighbors to be stuck in TwoWay
Ben> state?
Ben> I configured a set of 15 virtual routers w/OSPF connected in
Ben> interesting ways. Most of the nodes are connected to a bridge
Ben> object (roughly directly connected), and other connections form
Ben> a mesh. Most routers have several redundant paths through the network
Ben> between any two nodes.
Ben> Several of the instances connected across the bridge stay in TwoWay
Ben> state, but some of them work. As far as I can tell, the hello messages
Ben> are being send properly even from the guys in TwoWay state.
Ben> I checked IP connectivity with traceroute, and it all seems to be right
Ben> (ie, node 99.1.1.6 should be able to talk to 99.1.1.3).
Ben> [root at lf1016-55 ~]# traceroute -n -i 3.16.3 99.1.1.6
Ben> traceroute to 99.1.1.6 (99.1.1.6), 30 hops max, 40 byte packets
Ben> 1 99.1.1.6 2.785 ms 2.768 ms 2.756 ms
Ben> Assuming its not normal for them to be in this state, can you
Ben> give me an idea of where to look to start debugging this?
Ben> root at lf1016-55> show ospf4 neighbor
Ben> Address Interface State ID Pri Dead
Ben> 99.1.1.9 3.16.3/3.16.3 TwoWay 127.1.0.9 128 33
Ben> 99.1.1.10 3.16.3/3.16.3 TwoWay 127.1.0.10 128 34
Ben> 99.1.1.6 3.16.3/3.16.3 TwoWay 127.1.0.6 128 35
Ben> 99.1.1.2 3.16.3/3.16.3 TwoWay 127.1.0.2 128 35
Ben> 99.1.1.12 3.16.3/3.16.3 Full 127.1.0.12 128 36
Ben> 99.1.1.11 3.16.3/3.16.3 Full 127.1.0.11 128 36
Ben> 10.1.3.1 1.3.3/1.3.3 Full 127.1.0.1 128 30
Ben> 10.2.3.2 2.3.3/2.3.3 Full 127.1.0.2 128 35
Ben> 10.3.4.4 3.4.3/3.4.3 Full 127.1.0.4 128 31
Ben> 10.3.5.5 3.5.3/3.5.3 Full 127.1.0.5 128 33
Ben> 10.3.9.9 3.9.3/3.9.3 Full 127.1.0.9 128 34
Ben> root at lf1016-55>
Ben> Thanks,
Ben> Ben
Ben> --
Ben> Ben Greear <greearb at candelatech.com>
Ben> Candela Technologies Inc http://www.candelatech.com
Ben> _______________________________________________
Ben> Xorp-hackers mailing list
Ben> Xorp-hackers at icir.org
Ben> http://mailman.ICSI.Berkeley.EDU/mailman/listinfo/xorp-hackers
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