DID with VG224

Unanswered Question

Hi all,

Can VG224 pass DID info to FAX card attached to its FXS ports? I want to replace a PBX with CCM4.1. The PBX has 4 analog lines connects into a Faxmaker/Brooktrout server. Fax is coming into a range of DID on a PRI to the PBX. The PBX then routes the call to one of the analog lines and Faxmaker routes the fax to the designated party based on the DID sent to FAXmaker.

I checked all documentation. all I found was caller ID support for VG224 but no mentioning of DID. Can this be done with VG224 or I will need something else.


I have this problem too.
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jason-calbert_2 Fri, 02/09/2007 - 09:32

I have a VG 248 and I believe the 224 is the same. There is not a place on the box to put an FXS card.

What you are wanting to do though is very possible. Think of a VG224 as a phone that you can put 24 extentions on. So basicly you will have a DID range that hits your PRI then hits callmanager. Callmanager treats this just like a phone so it hits the VG224 which then converts back to analog to your FAX server.


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Paolo Bevilacqua Fri, 02/09/2007 - 09:54

Hi PC,

seems like you would need an FXO port that can generate DID, like apparently the PBX is doing.

It does not appear that the VIC-FXO card can do that, neither the VG224.

It appears that DID is supported on the IAD2420, but I'm not familiar with that device.

Perhaps you want to investigate if the faxmaker can be interfaced with a more common interface, like ISDN BRI or E&M. That would let you pass DID without problem using a router and VIC cards.

Thanks for the quick replies. I know how to configure a route-pattern to send all inbound faxes in the DID range to the VG224. My question is really on if the VG224 can relay the called DID to the fax modem on the Faxserver so that it can be routed appropriately to the corrct parties based on the DID passed down.

Currently the FAXmaker server has a Brooktrout 4-port analog card it it is geeting DID via these analog trunk ports from the PBX. Is there a way to do the same with Cisco Callmanager?

Appreciate the help and thanks in advance.

Paolo Bevilacqua Fri, 02/09/2007 - 12:54

Hi PC, doing DID does not depend on the callmanager only, your hardware must be capable of relaying DID,

As I said before either you get one device capable of doing that, or see if the broktrout have another mean to connectm other than DID, that you can accomodate on a simple cisco GW.

Worst case you can leave the PBX to do "did coneversion" and connect the GW via FXS-FXO to it.

jason-calbert_2 Fri, 02/09/2007 - 20:35

My opinion the VG224 will work. Let me explain why. A Fax call comes in your PRI whether that PRI is MGCP or H323 it is sent to callmanager for processing. Lets assume that the DID number is 1000. One of the VG224 lines is assigned the number 1000. Callmanger through it's call routing sends the 1000 DN to the VG224. The VG224 converts this from Digital back to analog which the Fax servers modem should understand.

I have a similar setup where I have a block of DID's that must call a server with modem banks in them using the VG248 and this works perfectlly.


Thanks for your reponse Jason. I understand your explaination and it will work like you explained. Having a DID assign to any one port on VG224 and route the fax to that port is the easy part.

One key thing I want but missing from your post is: I dont want to assign one DID to one of the lines on VG224 but a range of DID to one or more lines. The DID information is preserved when it hits the Faxserver so that the faxserver can make routing decision based on the DID information. Can VG224 pass the DID to the faxserver?

Sorry for not being clear from my previous questions.

Paolo Bevilacqua Sat, 02/10/2007 - 03:20

Hi Jason,

What you are missing is that there is a signaling protocol called DID, that consist in outpulsing from three to five digits on analog lines, from CO to user, beside a off-hook confirmation like groundstart or wink. From the CO point of view, these are outgoing lines only, and no calls can be placed inbound. Remember also, these lines will not have ring current.

The current fax solutions makes uses of this for further routing the faxes.

As fas as I know, the only cisco hardware that supports DID generation, is the IAD2430. If I'm wrong, I will be happy to be correct by a documented source.

Paolo Bevilacqua Sat, 02/10/2007 - 04:48

I have apologize for having spoken too fast, as I got a little confused too.

Indeed I think a regular FXO card will work connected the Brooktrout card.

The theory of operation for DID lines is as follows:

A DID line (better called a trunk), is a circuit in which loop current is generated by the user, seizing is made by the CO with loopstart, and digits are sent from CO to user premises. Optionally, user can send a wink (battery reversal) to the CO to acknowledge that has seen the seizing and selection shall begin.

See for an explanation: http://www.imecominc.com/downloads/whitepapers/analog_DID.pdf

Now, these characteristics are the exact opposite of the regular FXO card used to connect to CO or PBX. In fact, these are so similar to FXS, that cisco supports DID (in "receiving mode" on FXS cards, because these that have current generation.

The consequence is that to provide DID service, we will use an FXO card (any type, 2 or 4 ports should work), the only limitation is that we can only use use loopstart signaling, and immediate sending of digits.

I haven't tried this in the lab yet, but I will as soon I have a chance.

Has anybody gotten this to work yet because I'm in almost the exact same situation, I have the following - 2811 with 1 PRI interface (incoming calls from the PSTN) and 4 FXS interfaces that connect to a brooktrout card. The brook trout card is station side, so it EXPECTS dial tone, and if sent, can accept DID. I want to take a call from the PSTN that can come into a range of 50 DID numbers, and then send that back out to one of the FXS ports, but the FXS port HAS to preserve the original called party. Currently it just rings and the fax server answers and then drops the fax into the 'everybody' pile because it's not been given any DID infomration to route the FAX to a user. Other PBX's must be able to do this or Brook Trout wouldn't offer a card that was able to work this way. Anybody have any input? I have a TAC case open but I thought I would check here while I'm waiting.

Paolo Bevilacqua Mon, 04/23/2007 - 10:22

Hi Chris,

Cisco FXS should be able to play tones and DID the called number, it may work however this is not real DID as brooktrout describes in the document above.

Real DID per telco standard is no dial-tone, loop current provide by user, and delay or wink-start to send digits. That would require FXO or even better, E&M on the cisco side.

I know what you're saying, I've tried to change the signaling type from loop to DID wink, imediate, delay-dial etc, but those all ring busy. The fax card in the GFI software is set to DID, but it's just taking the fax at the front door and not routing it (so to speak). The way I'm setup right now (and I've tried this a few other ways with the same result). I have a PRI that when people on the outside call (123)456-7890 (example number) the last 4 digits hit my PRI interface, so the PRI interface see 7890, which is routed to CallManager for Digit analysis (The PRI is an MGCP interface). I have an H.323 gateway setup as the IP address of the router where the FXS card is installed, I have a route pattern in CallManager for 7890 that points to the h.323 gateway. I have dial peer in the gateway that does the following:

dial-peer voice 123456 pots

destination pattern 78..


forward-digits all

When I call 7890 from the outside, or just pickup a station phone and dial it, the call connects to the fax server but doesn't send any original called party information (that I can tell) to the fax server.

MarkMonteleone Mon, 04/23/2007 - 19:58

I am not sure totally about the H323 functionality in this design, as its relational to CallerID. However with the proper minipulation of the RouteList Details, you should be set.

I had a TAC case open on this yesterday and here's what we came up with:

The PRI where the calls are originating from can stay MGCP, the FXS ports if they are setup as MGCP won't pass caller ID, so I removed them from the MGCP config and set them up as h.323 and created an h.323 dial peer for them. TAC agreed that this was the proper way to set them up.

The problem I have now is with outbound dialing. I setup a VOIP dial peer and if I add a connection PLAR statement to the FXS port in h.323 mode it will dial, however since this is a FAX machine a plar isn't really what I want. I think what I'm going to end up doing is dedicating some of the ports to incoming (h.323) and some to outgoing (MGCP) From what the person installing the FAX software tells me, he doesn't see the DID number routing in on the logs, but from the Debug output that the TAC engineer ran the DID is being passed.

Paolo Bevilacqua Tue, 04/24/2007 - 05:35


I do not see what caller-id has to do with the problem, as we are talking about DID, that is part of the called number. Caller-id is the calling number instead.

I agree that switching to H.323 should make things easier. On an FXS port you can support bidirectional, you don't need a connection plar, just a dial-peer voip outbound.

I'm not surprised that the fax card in FXO mode does not see the digits sent from the VG. Normally dialing digits are are not recognized by FXO equipment. If the fax card was set to be in true fxs/did mode, it should recognize the digits.

Paolo Bevilacqua Tue, 04/24/2007 - 04:15


the problem is on the analog signaling, your PRM/CCM/h.323 appears to be fine.

In order to pass digits the port on the cisco router must be FXO, or possibly E&M.

it must not be FXS/DID, this is used when the router is meant to receive DID digits, not send them.

If you read the document by brooktrout linked above you will understand the working of Analog DID and why you need FXO on the router side when originating DID.

All this assumes that the fax card you are using supports analog DID as mentioned above.

Hope this helps, please rate post if it does!


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