Source bridge error

Question

I have a simple DLSw config that doesn't seem to be working. The peers are up, but when the "debug source bridge" command is issued the following appears on the screen...
Error only happens on R2
Oct 18 09:58:22 EDT: SRB0: explorer enqueued (srn 116 bn 2 trn 400)
Oct 18 09:58:22 EDT: DLSW: explorer duplicate ring violation C630.1902.0740
Oct 18 09:58:22 EDT: SRB0: duplicate ring violation, s: 8020.00d7.91b3 d: ffff.ffff.ffff rif: C630.1902.0740
Oct 18 09:58:22 EDT: SRB0: explorer enqueued (srn 116 bn 2 trn 400)
Oct 18 09:58:22 EDT: DLSW: explorer duplicate ring violation C630.1902.0740
Oct 18 09:58:22 EDT: SRB0: duplicate ring violation, s: 8020.00d7.91b3 d: ffff.ffff.ffff rif: C630.1902.0740
My config is very straight forwared
R1
source-bridge ring-group 400
dlsw local-peer peer-id x.x.x.1 promiscuous
interface Loopback0
ip address x.x.x.1
interface TokenRing0/0
source-bridge 1 1 400
source-bridge spanning
R2
source-bridge ring-group 400
dlsw local-peer peer-id y.y.y.1
dlsw remote-peer 0 tcp x.x.x.1
dlsw bridge-group 5
interface Loopback0
ip address y.y.y.1
interface Ethernet0/0
bridge-group 5
interface TokenRing0/0
source-bridge 116 2 400
source-bridge spanning
bridge 5 protocol ieee
The error only happens once the source-bridge spanning command is issued on the Token-Ring interface (on R2). From what I understand you need it in a DLSw setup to forward the single route explorer frames.
The client cannot seem to bring up a circuit so I am not sure if there is a configuration problem or not. The debug looks like a broadcast to me...so perhaps there is something wrong with their local config. I guess I just want an answer to what the debug really means...because I cannot find anything on it...Cisco or the Net.
Thanks...
Brett

Answer 1

Brett,
the error message is making you aware of the fact that a certain frame is due to be forwarded onto a ring number it already has an entry for in its rif.
However in certain situations this is also seen in working environments due to the inner working of the cisco source bridging code.
Are you sure that there is no duplicate source-bridge path? If yes, ignore the message.
If the error message is only seen when you use source-bridge spanning to forward single route explorers on the tokenring than you can do the following. Assuming we are talking about sna in this example:
dlsw allroute-sna
in this case dlsw will forward explorers outbound towards the tokenring as allroute explorers for sna on a tokenring interface. The default is as single-route explorer.
However inbound into the router it is purely dependend on what the end system does. If the end system, the client, starts with a single route explorer you still need source-bridge spanning on the interface, otherwise dlsw will not see the frame.
How does the setup physcially look like?
Is your client on the tokenring or on the ethernet interface attached to dlsw?
I understand from your description that the client is behind R2, so when you issue a show dlsw reachability
can you see the client?
debug dlsw reach verbose
should give you an idea if the client tries to start a session and with what dmac.
Is dlsw trying to start a circuit? I.e. in what state is the circuit if there is one?
show dlsw circuit history detail can give you some more ideas what happened, if the router tries to start a circuit and it is not successfull. However you need to know a great deal of dlsw to fully understand that output.
A sniffer on the tokenring will certainly show if the client tries to start a session and with what dmac.
There are lots of possibilities why this might not work, so it is most likely the best to open a case with the tac and work the issue till conclusion.
thanks...
Matthias