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Connecting modem to C7206

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by cloudd 1 view

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Hi all,
I'm trying to connect Cisco 7206 router to modem to accept dial-in connections. The modem uses the old serial cable (RS232 25 pin). I used the RS232 25 pin - 9 pin + console cable to plug it into the AUX port. However, the modem still does not pick up the call. Is this the right way? if not, can anyone tell me if there is any ready-made cable in the market or the cable pinouts if I were to custom-made this? Thanks.

3 replies

by road-dog

Even if your cable between the modem and the router is bad, the modem should still pick up inbound calls and negotiate.

If it is not, make sure that AA (autoanswer) is configured on the modem. Also, in an office environment, the PBX may have the inside extensions det as digital rather than POTS (plain old telephone service). If it is digital, the modem will not work and might be damaged.

Plug the modem into a jack being used for a fax machine. Power it up and call it. If it does not answer, the modem needs AA on or replaced.

by guruofdos

How many times do I have to explain to people?!!!

RS232 is a standard which defines not only the serial data protocol, but the connector as well. By definition RS232 MUST use a 25 pin D Type connector. The 9 pin connector is a reduced serial portwhich uses a subset of the RS232 standard and is actually an AT serial port...

Anyway....there are two types of RS232 device. DTE and DCE. DTE is Data Terminal Equipment and DCE is Data Carrier Equipment. RS232 or serial Modems are ALWAYS DCE. Most computers or teletypes are DTE and plotters, printers or in your case, the router could be either. DTE to DCE connections require all pins to be connected one-to-one. That is Pin 1-1, 2-2, 3-3 etc. DCE-DCE or DTE-DTE require a crossover cable. ForRS232 (25 Pin) that means 1-1, 2-3, 3-2, 4-5, 5-4 6-8, 7-7, 8-6 and possibly additional connections. 9 pin serial ports transpose the input and output connections so that although a PC is DTE, the pins are actually connected as DCE....another of IBM's contributions to messing up standards!! I suggest contacting Cisco and asking THEM what cable you need!!!

by road-dog

tTheir routers ship with a baggie containing a couple of RS-232 (RJ to DB-25 ) type adapters for console / modem connections. Oddly enough, the 8-conductor cable is a rollover, pins 1-8 crossed to 8-1. Don't ask me why unless you enjoy blank stares.

One of the adapters is labeled PC, the other, modem.

Those console cables have a tendency to end up as frame relay or T1 WAN connections when the equipment is messed with by the uninitiated. I had to fly from Florida to Detroit once on a network outage and that was the culprit.

The original problem was that the modem was not pocking up inbound calls, I suspect so the preceeding is academic and I stand by my previous post.

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