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Community Member

how to keep DTR high ?

2611 router with wic-2T sync/async cards connected to 3com Courier external modems with Auto Answer enabled on modems to allow dial in users to access network,the problem is that DTR sometimes goes low and this leads to failure of auto answer so the users modems keeps ringing with no answer,it sometimes works ok but then all of a sudden DTR goes low,how can I force a DTR high from the the router to the modem or enable somesort of trigger on the router to get it back high again?...thanks in advance

3 REPLIES
Community Member

Re: how to keep DTR high ?

If you have the ability, I would tie DTR high with a jumper in the modem connector (tie tie it back to DSR for example). If that isn't an option, at least make sure that you have the 'no pulse' or 'pulse 0' command on your interface as well as 'no keepalives' so that your interface will be blind to the line conditions. I think the interfaces tend to go into an idle mode if they are set for keepalives and don't get them but the behavior seems to be erratic from one platorm to the next, one IOS to the next, etc. Also, I find that many modems can be configured to assume that DTR is always high.

Community Member

Re: how to keep DTR high ?

Hi Samir,

Basically your case is related to dial in ras case. You have to confgure your modem properly. As it seems that your modem is not properly bind with the router. Your modem profile setting is not properly matched to receive the call

you can try out this command to solve the prob on the line interface

Modem autoconfigure discovery

This command helps router to find out the modem profile and configure itself accordingly.

Once done, confirm.

Vinod Gupta

Community Member

Re: how to keep DTR high ?

Hi Samir,

You can also use an AT command string on the modem to basically ignore DTR. This command is "&D0". Dip Switch 1 on the courier also deals with DTR responses.

Dan

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