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New Member

Internal t1 CSU/DSU

I have an old router that is intermittenetly passing traffic. I recently put a 1721 with a t1 csu/dsu card in its place. It is a 64K frame relay line. The status shows "Serial0 line is down, line protocol is down". I have read http://www.cisco.com/en/US/tech/tk713/tk628/technologies_troubleshooting_procedures09186a00800a758d.shtml. The serial line was up with the old router. I tried placing the csu/dsu in both wic slots and the status never changed.

1. Is there a command or setting to make the status change to "Serial line is up, line protocol is down" without a CD signal from the Telco? What about without a cable attached to the csu/dsu?

I could not find a command or any csu/dsu settings to do this without a CD so I am guessing the t1 card is faulty.

Thanks,

RJ

  • Other Network Infrastructure Subjects
5 REPLIES
Silver

Re: Internal t1 CSU/DSU

you can try 2 things

'no keep ' under the serial interface and/or the 'ignore dcd ' command

New Member

Re: Internal t1 CSU/DSU

If you've verified that the DLCI, lmi type etc. are all correct call the phone company and make sure they can loop to both CSUs.

New Member

Re: Internal t1 CSU/DSU

Thanks for the responses. I was really trying to find out if the Serial interface could be up without a cable attached. For instance, "Serial0 line is up, line protocol is down". The only way to have this status is to have a signal into the CSU/DSU itself, correct? I was wondering because the T1 card in my 1721, was status of down/down when 5 minutes before putting the router in, the line was functional with a differenet router. This leads me to believe there is a hardware failure with the T1 card.

Thanks,

RJ

Silver

Re: Internal t1 CSU/DSU

did you configure the card ?

'service-module t1 timeslots xx ' under the serial interface the xx is the amout of DS0's you are using

New Member

Re: Internal t1 CSU/DSU

Yes, I configured this. But this will not bring the status, to "Serial line is up, line protocol is down". I am pretty sure you need a valid Carrier Detect from the telco via a CAT5 cable to the CSU/DSU to attain this status.

Thanks,

RJ

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