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New Member

sdlc device dosen't work well

Hello,

ATM device---modem---modem---2600 router -----7500 router ---HOST

2600 connect to modem with RS-232 DTE cable.

We see dlsw cir is connected, but it dosen't work well. It disconnects very often. After we change cable to RS-232 DCE cable to modem in 2600 router, then ATM work well.

The cofiguration is as below:

inter s0/1

encapsulation sdlc

no keepalive

nrzi-encoding

sdlc role primary

sdlc vmac 4000.2600.1900

sdlc poll-pause-timer 100

sdlc address A9

sdlc xid A9 01701912

sdlc dlsw A9

When 2600 connect to modem with DCE cable, we add the command "clockrate 9600".

Should we need to modify configuration when cable is DTE??

Regards,

May

4 REPLIES
Cisco Employee

Re: sdlc device dosen't work well

When the router interface is the DTE interface, the clockrate 9600 will not be in effect since the clockrate is driven from the DCE interface. The problem here is distance-adding the modem creates delay and distance. Technically, at 9600, the length is 50 ft for RS232 and the delay introduced by the modem probably accounts for the equivalent of 50 ft. However, with a quality cable, you probably can run a RS232 or V35 cable to 100 ft and run 4800 clockrate on the router without modems.

Cisco Employee

Re: sdlc device dosen't work well

Hi,

I am a bit pusseled with the statement that you changed the cable from DTE to DCE between the router and the modem. Typically the modem provides the clock in such an environment and the 2600 should be DTE.

If for any reason the modem does not provide the clock and the router needs to provide the clocking than you need to have a dce cable attached to the router and you must have a clock rate configured on that interface.

The router will not allow you to configure a clock rate on a DTE interface.

I guess you need to get a better understanding how your modems are configured and how they are supposed to work.

The config sniplet you provided looks ok as far as i can say.

thanks...

Matthias

Cisco Employee

Re: sdlc device dosen't work well

Hi May,

You can only have one clock source, either the modem or the router. With the DTE cable, the modem should be providing clocking. It sounds like there is a problem in this area with the modems. The modem connected to the ATM would provide clock to the ATM and the modem attached to the 2600 would provide clocking to the 2600. Both modems should be set for the same clock rate, which should be 9600 it seems.

The 2600 only supplies clock when it has a DCE cable and clock rate is configured.

Best regards,

Jim

New Member

Re: sdlc device dosen't work well

Thanks your reply!!

I went to customer site and tried by myself this afternoon.

1. 2600 & wic2T & DTE cable --Modem to Modem--ATM device

configuration as below:

inter s0/0

encapsulation sdlc

no keepalive

nrzi-encoding

sdlc role primary

sdlc vmac 4000.2621.8800

sdlc address A1

sdlc xid A1 01700111

sdlc partner 4000.3745.0002 A1

sdlc dlsw A1

I debug sdlc even and packet, messages as below:

00:00:48: Serial0/0 SDLC output A193

00:00:51: Serial0/0: SDLC T A1 SNRMSENT 0xCB54 T 12

00:00:51: Serial0/0: SDLC O A1 SNRMSENT (2) SNRM P s: 0 r: 0 rr: 0

==> ATM Device can't work

I replaced 2600 with 2501 router, ATM device can work well.

2.2600 & wic2T & DCE cable -- ATM device

configuration as below:

interface Serial0/0

no ip address

encapsulation sdlc

no keepalive

nrzi-encoding

clockrate 9600

sdlc role primary

sdlc vmac 4000.2621.8800

sdlc address A1

sdlc xid A1 01700111

sdlc partner 4000.3745.0002 A1

sdlc dlsw A1

debug sdlc even and packet

show log as below

00:02:44: Serial0/0: SDLC I A1 CONNECT (2) RR P/F 6, [VR: 7 VS: 6]

00:02:44: Serial0/0 SDLC input A1D1

00:02:44: Serial0/0: SDLC T A1 CONNECT 0x285AC P 0

00:02:44: SDLC: Sending RR/RNR at location 4, Serial0/0 A1

00:02:44: Serial0/0: SDLC O A1 CONNECT (2) RR P/F 7 s: 6 r: 7 rr: 6

00:02:44: Serial0/0 SDLC output A1F1

And ATM can work well.

Anyone has the same experience??

Dose 2600 router support DTE cable & modem with SNA device??

Regards,

May

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