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Async dial up connections dropping between 2650's and AS/5300

Hello There,

I having some trouble with async dial backup connections not staying connected between 2650's and AS/5300. Problem is not with dialing AS/5300 but with dropping off anywhere from 20 to 35 seconds after the connection with AS/5300.

The 2650's use a ISDN PRI connection to a AS/5300. We use this for a dial backup solution when we lose a frame-relay circuit. 2650 is dialing with a US robotics Courier Modem connected via the AUX port. I have verified that the modem answers and is able to dial out .

Timeout value is set to 300 seconds on 2650 so idle timeout is not the problem.

The 2650 uses PPP chap for authentication and I would suspect that this is where the problem lies. I know that the Hostnames have to match between the 2650 and the AS/5300... the name of the AS/5300 is correctly specified on the dialer map command on my 2650.

I have tried on occassion to delete the entry for the 2650 out of the AS/5300 and then readding it..This helps on occassion. I have also had a little success deleting the dialer map command out of the 2650 ...changing the phone number and then adding it back...

Also some are dialing a number that is a local call some are dialing a toll free number...both numbers are going to a PRI on the AS/5300..

I have not really been able to determine where the problem lies...authentication...AS/5300 or modems. Unfortunately I'm also very limited in the debugs I can run because it tends to cause problems..especially in the AS/5300.

I have about 40 of these 2650's in our network..Only having trouble with 5 or 6...Configuration info in them is the same..except for ip addresses and Hostnames...all run same IOS c2600-is-mz.121-5.T12.bin

I have looked through all of the IOS caveats for this release and have found nothing in particular.

I would appreciate some troubleshooting suggestions if anyone has them. Thanks


Re: Async dial up connections dropping between 2650's and AS/530

Ideally will need to see some debug outputs on both ends to determine the cause of call failures. Also the relevant parts of running configs will be useful. If the call drops after around 20 secs means it might not have even connected fully.

on 2600: deb chat / deb dialer / deb modem / deb ppp nego

on as5300: deb isdn q931 / deb modem / deb modem csm / deb ppp nego

If you are using AAA server, then add deb aaa authen / deb aaa author

Thanks, Mak.

Community Member

Re: Async dial up connections dropping between 2650's and AS/530


I'll get some config info (without passwords) to place in this discussion. I would also like to mention that at times power failing the 2650 has also resolved the problem. Only thing I can figure there is that the aux port on the router gets reintialized when router is power failed.

Which brings me to another question. Can I not reintialize the aux port manually with clear line aux 0 command?...Power failing the router is disruptive. Does clear line aux 0 do the same thing to the aux port that a power fail would do?


Re: Async dial up connections dropping between 2650's and AS/530

This is a strange behaviour you are running into. Does the call work fine if we just power cycle the modem instead of power cycling the router?

What does "show line" indicate? Maybe the line has not yet cleared & is incorrectly in an Active state, in that case "clear line aux 0" will help.

Thanks, Mak.


Re: Async dial up connections dropping between 2650's and AS/530

Sounds like the modem is getting configured during powerup but not when the line disconnects. Are you using script reset on the aux line?

Community Member

Re: Async dial up connections dropping between 2650's and AS/530

Occassionally a power fail of the modem itself will help...I've tried a bunch of different things.

One thing I have noticed is that I have a chat-script in my MC3810's which seem to have less trouble connecting than the newer 2650's. 2650's have no chat-script coded...BUT If this is the problem how come 34 out of (40) 2650's work pretty well?

As far as a show line is concerned...The 2650 barely stays connected long enough to find out....I'm usually trying to watch the AS/5300 with a sh isdn active command while I have the dial process going I'll have to admit I need to try that.

I do not know about script reset...I'll have to look into it...Thanks

Community Member

Re: Async dial up connections dropping between 2650's and AS/530

Just curious if you ever got this problem resolved? I have a similar environment (2561XM routers to PRI connnected AS/5300 - selective routers do physically connect on dial-backup but I get no PPP sessions or occasionally PPP sessions with timeouts). In my case the problem seems to depend on the type of modem used - courier V.Everythings work but courier 56Kbs do not.

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