t37 fax onramp/offramp

Hi all. first of all, I don't have any knowledge of voice, because I'm an RS guy. but I'm in the process of configuring the T.37 onramp/offramp and need some help. my config is works in onramp portion. so my faxes are going to mail server as TIFF images and this works with inside faxs and outside ones.

but for the offramp portion, I can just use it inside of my network, which means I can only send mail messages (which will be sent to physical fax devices,) on any of inside computers that the fax device is there too. I need to be able to send mail messages on one of my inside computers to external fax devices. the operator of PBX wants me my inside telefone number! it seems that I need to provide him with a internal number (I think ANI number) , so he can get this number and route the call to the outside world. my voice-related portion is here. any help would be greatly appreciated. tnx guys.


ip domain name test.fax

ip name-server


isdn switch-type primary-net5


voice-card 0


fax receive called-subscriber $d$

fax send transmitting-subscriber $s$

fax interface-type fax-mail

mta send server port 25

mta send subject "mail from fax"

mta send origin-prefix "Eks-pa power Fax System"

mta send postmaster [email protected]

mta send mail-from hostname c2921.test.fax

mta send mail-from username $s$

mta send return-receipt-to username $s$

mta receive aliases test.fax

mta receive maximum-recipients 48

mta receive generate permanent-error



 service fax_detect flash:app_fax_detect.

 service onramp-app flash:app_faxmail_onramp.

 service offramp-app flash:app_faxmail_offramp.


controller E1 0/0/0

clock source internal

pri-group timeslots 1-30


interface Serial0/0/0:15

 no ip address

 encapsulation hdlc

 isdn switch-type primary-net5

 isdn protocol-emulate network

 isdn incoming-voice voice

 no cdp enable


voice-port 0/0/0:15


mgcp profile default


dial-peer voice 29 mmoip

 service offramp-app

 information-type fax

 incoming called-number .

 dsn delayed

 dsn success

 dsn failure


dial-peer voice 54 pots

 destination-pattern .

 port 0/0/0:15

 forward-digits all


dial-peer voice 33 pots

 service onramp-app

 incoming called-number .



dial-peer voice 99 mmoip

 service fax_on_vfc_onramp_app out-bound

 destination-pattern .

 information-type fax

 session target mailto:[email protected]


  • timaztimaz ✭✭

    while we send an fax-email message via our mail client, we don't/cannot specify our own tel number (I think that is ANI number), so we need to specify one on the router, so the PBX system sees our initiated fax-email message as if it is cooming from "xx" number and route that to the external PSTN fax machines. as I know this is digit processing or manipulation process. can someone help me on this, so I can specify an ANI number for my fax-mail message? tnx

  • timaztimaz ✭✭

    it seems there are no voice experts here who know about t37 fax anymore !!!

  • timaztimaz ✭✭

    I tried to configure T37 onramp/offramp fax in my network but after several attempts I failed to apply it completely and just portion of that worked well. despite describing the scenario in many forums (like here), I got nothing!

    anyway, I'm going to test it in a simple form. I mean, I want to connect my edge router to PSTN line via an FXO port and via ethernet to internal network. my internal network has many physical fax machines that have gotten their internal tel numbers (like 866, 867, ...) from PBX . so can I use this scenario to configure the router to support these fax machine, or I should connect fax machines directly to router through FXS ports? tnx. 

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