Not able to FAX one external number

Unanswered Question
May 16th, 2007

I have a strange FAX issue, where a FAX machine connected to a VG224 can send/receive FAX to any number but is not able to send one outside number a FAX. It can receive FAX's from them fine, just not send. The FAX machines phone or a phone plugged into the FAX phone line can call the # fine so there is not a CSS issue, etc.

The FAX machine is plugged into a VG224 with IOS 12.4(11)T , the VG224 is configured as SCCP (stcapp) and we have tried setting the port capabilty to modem passthrough and not with no change.

The PSTN Gateway is a Cisco 2821 with a PRI, it is MGCP and running IOS 12.4(9)T and has FAX relay disabled.

We have tried 7 different FAX machines of different models and neither are able to call this particular outside FAX machine when going over IPT. When the FAX machines are plugged into a traditional analog circuit there is not a problem and the FAX works fine.

Any ideas?

I have this problem too.
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thisisshanky Wed, 05/16/2007 - 10:14


Did you try using H323 or MGCP on one port on the router and use fax relay instead and see if that helps any ?

Erick Bergquist Wed, 05/16/2007 - 10:17

Well, this is production so kind of hard to convert the main 2821 Gateway (PSTN) from MGCP to H.323.

I can look into changing one of the VG224 ports. The stcapp does not support relay, only passthrough. I've never had good luck with relay anyway with fax and modem calls.

thisisshanky Wed, 05/16/2007 - 10:27

I am using H323 on my pstn gateways, all my vg224s are mgcp. I am using t38 for faxing. Works just fine on almost every vg224 port. What i meant in my previous post is ofcourse keeping mgcp as it is on the pstn gateway and simply convert one port on the vg224 to h323.

Erick Bergquist Wed, 05/16/2007 - 11:06

I also found out they have same problem when trying to FAX to this # from machines off other voice gateways and ATAs. Common factor is the 2821 MGCP gateway with the PRI and call manager.

thisisshanky Wed, 05/16/2007 - 11:14

Do you mind sending the number to which you are faxing this. I can give it a try with the setup here. Of course this wont prove any thing but atleast see if using a callmanager/gateway/voip solution creates problems or not.

2smith Thu, 05/17/2007 - 05:07

I had a similar problem and cured it by entering 'mgcp fax t38 gateway force' on the MGCP gateway

Erick Bergquist Thu, 05/17/2007 - 06:59

Ok, but we are not doing T.38 here but will try as soon as I get a chance.

I also disabled the redundancy for mgcp modem passthrough and that did not improve anything.

MGCP commands on gateway:

mgcp call-agent 2427 service-type mgcp ver

mgcp dtmf-relay voip codec all mode out-of-band

mgcp rtp unreachable timeout 1000 action notify

mgcp modem passthrough voip mode nse

mgcp package-capability mf-package

mgcp package-capability rtp-package

no mgcp package-capability res-package

mgcp package-capability sst-package

no mgcp package-capability fxr-package

mgcp package-capability pre-package

no mgcp timer receive-rtcp

mgcp sdp simple

no mgcp fax t38 ecm

mgcp fax t38 inhibit

Also have, no ccm-manager fax protocol cisco.


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