Want to configure 2800 series router to replace Adtran TDM-style configurat

Unanswered Question
Nov 6th, 2009

My customer is looking at an Adtran Atlas 550 to support a fax server application that I'm hoping can be done with a 2800 series router. I've tried several approaches, but cannot seem to get it to work.

1) Call from a remote Fax machine come into a CAS T1 connected to a VWIC on a 2800 router. There are 4 DNIS numbers supported on the CAS T1.

2) The call needs to be forwarded to a FAX server that connects as an analog station. There is a FXS/DID card also in the same 2800.

3) The fax server needs to answer the call and wink back to the telco to send DNIS.

4) The telco forwards DNIS to the router which will send it to the fax server which uses it to route the fax.

From the Adtran web site, this is a Q&A about this feature:

Q: How can I use the DNIS delay option of the TSU voice FXS cards to signal an off-hook condition back to the telco after a simulated delay needed to allow my called device time to answer? For example, my called device will be a Fax Server.

A: The TSU's network port is connect to the telco's T1 line. The FXS card uses its analog 2-wire ports to connect to (in this example) the fax server. When a call comes in from telco, the FXS card then sends ring voltage to the fax server. The fax server responds by answering the call. The FXS card winks back to telco that the server is ready for DNIS. At

the same time the FXS card winks, it starts counting down the time configured under the DNIS delay option. The fax server receives the DNIS tones and uses them to route the call to the appropriate fax machine. This procedure takes a few seconds to route and for the fax machine to answer. When the DNIS delay time has expired, the FXS card sends an off hook condition to the telco to finish connecting the call.

Issue: I want to avoid buying a Adtran 550 and would prefer to use one of my 300 2821 routers. Can this be accomplished?

FAX machine--pots---telco---CAS T1---2800--FXS--fax server.

The issue appears to be my traditional approach to this where the router receives DNIS and makes routing decisions - either local POTS or VoIP peers. The probem with this approach is that DNIS has already been collected by the router. Here is the T1 controller configuration and other info snip'd from the current configuration:

controller T1 0/2/0

cablelength long 0db

ds0-group 0 timeslots 1 type e&m-wink-start dtmf dnis

voice-port 0/2/0:0


voice-port 0/1/0


dial-peer voice 2530043 pots

incoming called-number 0043


port 0/2/0:0


dial-peer voice 92530043 pots

destination-pattern 0043

port 0/1/0

forward-digits all

I also tried the connect statement which essentially cross-connects the T1 to the pots line and made the FXS/DID port DID...like this:

voice-port 0/1/0

signal did delay-dial


connect fax-connect voice-port 0/1/0 t1 0/2/0:0

With this I get a busy signal whose cadence corresponds directly with the attached analog station ringing.

Any ideas?

I have this problem too.
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Paolo Bevilacqua Fri, 11/06/2009 - 07:54

From what I understand, the "analog station" was originally meant to be connected to a CO via analog DID line.

If so, the VIC-FXS/DID cannot be connected to the analog station, because its purpose is to be "station side" of an analog DID line, not "CO side". The main difference is that in analog DID, the station provides current loop, not the CO. So you would have two devices providing current loop, a bad thing without even entering further signaling details.

I would recommend you find exactly what are the analog station requirements and configuration options, then try to find a cisco solution that is compatible.

Goes without saying, the router itself, with or without additional software, can do an excellent fax server, but you and your customer likely have considered that already.

kbyrd Fri, 11/06/2009 - 08:34

Thanks for your response.

No, the analog fax server was not originally going to be connected to the CO....at least as far as this project is concerned. Maybe that was IBM's intent as they designed this analog fax card, however IBM says they have customers running with the Adtran Atlas 550 in the mix. I think most customers with these servers prefer digital CO lines for reliability and they use the Adtran to provide the cross-connect. Adtran says that it will work.

Maybe my problem is that I'm using a plain telephone for testing and should be using the actual fax server if it in fact supplies the current loop.

Thanks for the info...this could help.


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