05-07-2004 09:37 AM
Hi experts.
It's not the first time I configure DLSw, but this time I face a strange issue.
I'm trying to establish a peering between a Cisco 2621 (c2600-is-mz.120-5.T1.bin) and a Cisco 3745 (c3745-a3js-mz.122-13.T8.bin).
Configuration excerpts are copied below:
Cisco3745:
dlsw local-peer peer-id 192.168.245.252 promiscuous
dlsw icanreach mac-exclusive
dlsw icanreach mac-address 4000.XXXX.XXXX mask ffff.ffff.ffff
dlsw icanreach sap 0 4 8 C
dlsw bridge-group 47
dlsw bridge-group 49
Cisco2621:
dlsw local-peer peer-id 192.168.245.200
dlsw remote-peer 0 tcp 192.168.245.252
dlsw remote-peer 0 tcp 192.168.245.254
dlsw remote-peer 0 tcp 192.168.245.253 backup-peer 192.168.245.254 linger 10
dlsw bridge-group 1
I can successfully perform an extended ping between the two dlsw local peer id's, but the peer is always disconnected. The TCP connections seems to be established but the Cisco 2621 sends an RST message.
The output of "deb dlsw peer + deb ip tcp transac" captured on the Cisco2621 is attached.
Can you please help me to understand if I'm doing something wrong?
Thank you
michele
Solved! Go to Solution.
05-10-2004 04:38 AM
Hi Michele,
I see that the peer connection is halted with a reset. Check to see what line the AUX port is using on the router that sent the reset. If it is 65:
W2S-10.5-2612-A#sh line
Tty Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns Int
* 0 CTY - - - - - 0 0 0/0 -
65 AUX 9600/9600 - - - - - 0 0 0/0 -
Then as a test, configure:
line aux 0
no transport input
For reverse telnet, the router assigns TCP port 2000 plus the line number. This would make the aux port 2065, which is the same as DLSw. This can cause a conflict.
Best regards,
Jim
05-09-2004 05:42 PM
There is nothing wrong with your configs but the debugs do not show any reason for the RST.
I would try 2 things. Make sure that you are running the same level of IOS in both routers, preferable a current maintenance level and also try staticall coding the remote peer statement in the 3745 router and see if that makes a difference.
05-09-2004 11:45 PM
Hi Rona,
and thank you for your answer!
I've already tried to hard code the remote peer statement on the Cisco 3745... same result :-(
However, the Cisco 3745 is going to be the hub of about 120 DLSw sites (all of them are Cisco 2621 with the same IOS version), so the promiscuous option is the only viable one.
Looks like the only option I have is to upgrade the IOS version on the remote sites... hoping a new image will fit into the DRAM the routers are equipped with.
I will let you know the results.
Cheers
michele
05-10-2004 12:26 AM
Try this page for troubleshooting:
http://www.cisco.com/en/US/tech/tk331/tk336/technologies_tech_note09186a008009424a.shtml
HTH
05-10-2004 02:04 AM
Changed encapsulation type to FST and now the two peers are in CONNECT state.
Is FST as robust as TCP? What kind of issues could I face with this solution?
dlsw local-peer peer-id 192.168.245.200
dlsw remote-peer 0 fst 192.168.245.252
dlsw remote-peer 0 fst 192.168.245.254
dlsw remote-peer 0 fst 192.168.245.253 backup-peer 192.168.245.254 linger 10
dlsw bridge-group 1
Thank you!
michele
05-10-2004 04:25 AM
Hi,
first i think if fst does work but tcp does not than you should make an extra effort to understand why tcp does not work.
Take a sniffer trace from the attempt to bring the peer up. Do the debugging on both routers simultaneous.
debug dlsw peer
debug ip tcp driver
debug ip tcp transactions
to start. If you need help in troubleshooting and to interpret the debugging open a case with cisco tac.
The difference between tcp and fst peers is like this:
tcp has a tcp session between the two routers. it does do segmentation of large frames from the lan over a wan with a lower mtu. I.e 4k tokenring frames over a wan media with mtu 1500.
Tcp peers do local ack on the local llc2 sessions,
that means llc2 RR frames are locally acked and do not go over the WAN.
fst:
fst has no tcp session between the two peers. It does NOT do segmentation of large lan frames over a wan with a smaller mtu.
fst does NOT do local ack, llc2 RR frames are end to end.
Typically you need to configure the lf parameter on the remote peer statement for a fst peer. I.e. lf 1500 if you connect ethernets. Also you need to make absolutely sure that your WAN can carry a maximum ethernet frame + ip header (20 bytes) + fst header (12 bytes). If your WAN mtu is also 1500 and you get a maximum ethernet frame, say 1500 bytes, this will fail since you must add the extra headers, with fst there is no segmentation so every frame send individualy with the extra encap bytes attached to it.
So in this case you need to make sure that your WAN mtu is large enough. If it is a serial line or frame relay you can simply raise the mtu to 1600.
fst is typically used when you have a high bandwidth WAN media. In a scenario where you dont need local ack. If you have low bandwidth frame relay circuits than you can run into timeout situations without local ack.
fst is less cpu intensive than tcp. A good portion runs in the fastswitching path.
thanks...
Matthias
05-10-2004 04:38 AM
Hi Michele,
I see that the peer connection is halted with a reset. Check to see what line the AUX port is using on the router that sent the reset. If it is 65:
W2S-10.5-2612-A#sh line
Tty Typ Tx/Rx A Modem Roty AccO AccI Uses Noise Overruns Int
* 0 CTY - - - - - 0 0 0/0 -
65 AUX 9600/9600 - - - - - 0 0 0/0 -
Then as a test, configure:
line aux 0
no transport input
For reverse telnet, the router assigns TCP port 2000 plus the line number. This would make the aux port 2065, which is the same as DLSw. This can cause a conflict.
Best regards,
Jim
05-10-2004 05:12 AM
Thank you James for solving my issue!
The aux port is assigned port #65 and following your instructions the peers get connected!
Thank you very much!!!
michele
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