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New Member

T38 Fax Server to H323 Gateway (PSTN)

Right here goes, inbound faxing is working great, I have a fax server GFI Faxmaker running a Brooktrout SR140 FOIP boardless driver. Outbound faxing fails every time. Here is the config of the 2651XM router: -

FAXGateway#sh run

Building configuration...

Current configuration : 1994 bytes


version 12.3

service timestamps debug datetime msec

service timestamps log datetime msec

no service password-encryption


hostname FAXGateway



enable secret

no network-clock-participate slot 1

no network-clock-participate wic 0

network-clock-select 1 E1 1/0

no aaa new-model

ip subnet-zero

ip cef

no ftp-server write-enable

isdn switch-type primary-net5

voice-card 1

voice call send-alert

voice call convert-discpi-to-prog tunnel-IEs

voice service pots

voice service voip

fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback none


no call service stop

controller E1 1/0

pri-group timeslots 1-31

controller E1 1/1

interface FastEthernet0/0

ip address

duplex auto

speed auto

h323-gateway voip interface

h323-gateway voip h323-id 690470

h323-gateway voip bind srcaddr

interface Serial0/0

no ip address


no fair-queue

interface FastEthernet0/1

no ip address


duplex auto

speed auto

interface Serial1/0:15

no ip address

isdn switch-type primary-net5

isdn incoming-voice voice

no cdp enable

ip classless

ip http serve


voice-port 1/0:15

bearer-cap Speech

dial-peer voice 781453 pots

description Use this to dial any number out

destination-pattern .

progress_ind alert enable 8

clid network-number 690471

no digit-strip


port 1/0:15

dial-peer voice 690471 voip

description To FAX

destination-pattern 690471

session target ipv4:

session transport udp

codec g711alaw

no vad

dial-peer voice 1 voip

description incoming from FAX

numbering-type unknown

incoming called-number .

codec g711alaw

no vad


timer receive-rtp 1200

Attached are 2 files with ISDN q931 debug and DialPeer debugs

file 1 is a CSIM start that works, file 2 is a call originating from the FAX server that fails. I think it is a signalling issue but don't know where the responsibility lies to fix it, is it GFI/Cantata or Cisco or PSTN service provider?

Any help would be great, do I need to use a h323 gatekeeper? I really do not know what is causing the problem.




Re: T38 Fax Server to H323 Gateway (PSTN)

Fax pass-through is supported under the following call-control protocols:

• H.323

• Session Initiation Protocol (SIP)

• Media Gateway Control Protocol (MGCP)

The following URL may help you:

New Member

Re: T38 Fax Server to H323 Gateway (PSTN)

I have resolved this issue, the fax server was forcing all calls out to the PSTN as ISDN National, so the PSTN was not understanding the numbers dialed. I added ISDN maps to map the dialed numbers to National or international and changed my dial-peers to only send national and international numbers without prefix codes i.e drop the prefix '0' for national and prefix '00' for international and prefix local numbers with '1624' for local isle of man dialing.