[Xorp-users] Re: help establishing OSPF adjacencies

[Nick Feamster]

On Mon, Oct 17, 2005 at 02:11:25PM -0700, Atanu Ghosh wrote:
> Hi,
> 
> The messages of the form '[ 4251 +430 xrl_io.cc ...' are debugging
> output from OSPF. One of the things that they show are packets being
> sent and received by OSPF.
> 
> OSPF uses multicast on broadcast media to distribute LSAs (with a TTL of
> 1), so this behaviour is correct.

OK.  Thanks for the clarification.

> The TRACE messages are typically at the top of methods so they show the
> state on entry to the method. It is therefore correct that when a
> InterFaceUp event occurs that the state of the interface was down.
> 
> Could you try disabling Click and see if an adjacency is still not
> formed.

Yes, I think I did actually try that.  I removed it from the XORP
configuration, at least.  What should I configure in the FEA instead?
Do I need to configure multicast?  Also, when you say "broadcast media",
what do you mean?  I'd think that would mean the broadcast address of
the subnet, 128.31.1.255.  What's this 224... multicast address, and do
I need to configure something in XORP to make certain it's reachable?

> In order for an adjacency to be formed routers have to see each others
> hello packets. A hello packet contains a hello interval, a router dead
> interval and a list of other routers that have been seen on this
> interface. The hello interval and router dead interval have to match for
> an adjacency attempt to be made. As an optimisation on broadcast
> networks rather than forming an adjacency with every other router on the
> subnet a designated router and backup designated router are elected.
> The DR and BDR routers form adjacencies with all the routers and the
> routers in the other set form only two adjacencies.
> 
> Two routers with the default configuration should try and form an
> adjacency. You should see TRACE messages of this form:
> 
> [ . TRACE .] Event(HelloReceived) I.(fxp0/fxp0) N.(128.31.1.14) State(Full)
> [ . TRACE .] Event(2-WayReceived) I.(fxp0/fxp0) N.(128.31.1.14) State(Full)
> 
> I have replaced some of the output with '.'s.
> 
> If you are not seeing Event(HelloReceived) then they are not seeing each
> others hello messages. Note the state is Full in this example.

I definitely don't see these.

> After I saw you original message I went back and checked that
> adjancencies are still being formed and they are.
> 
> I found one thing a little puzzling the checksum for both routers for
> different LSAs is the same, is this the actual output?

No, I had a copy/paste error.  The checksums are different.

-Nick