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VoIP FAX Relay issues

Hello everyone!

I am experiencing some issues when working with T.38 Fax in my network. I am simply unable to send / receive any faxes. The topology is quite simple:

Branch VoIP Router --> Central VoIP Router --> E1s to Alcatel PBX --> PSTN

The Branch voip router is able to send and receive phone calls normally, passing through the central VoIP router, which has E1 interfaces in order to send those phone calls to the Alcatel PBX that offers the connectivity to the PSTN services.

When a fax machine connected to the Branch VoIP router sends faxes to a remote fax machine, the remote fax machine rings and answers the call, but the fax transmission is then aborted. I've tried different remote fax machines and none worked, either when sending or receiving faxes.

With reference to Phone calls, everything works perfectly. My only issue here is when trying to send/receive faxes. I am enclosing my configuration below:

card type e1 1 1

!

network-clock-participate slot 1

!

isdn switch-type primary-qsig

!

voice-card 0

dspfarm

!

voice-card 1

dspfarm

!

voice call send-alert

!

controller E1 1/0

clock source line primary

pri-grouptimeslots 1-31

!

controller E1 1/1

pri-group timeslots 1-31

!

interface Serial1/0:15

noip address

encapsulationhdlc

isdnswitch-type primary-qsig

isdntimer T310 120000

isdnprotocol-emulate network

isdnincoming-voice voice

no cdp enable

!

interface Serial1/1:15

noip address

encapsulationhdlc

isdnswitch-type primary-qsig

isdntimer T310 120000

isdnprotocol-emulate network

isdn incoming-voice voice

no cdp enable

!

voice-port 1/0:15

no non-linear

novad

playout-delaynominal 100

playout-delayfax 100

playout-delaymode fixed

bearer-capSpeech

!

voice-port 1/1:15

no non-linear

novad

playout-delaynominal 100

playout-delayfax 100

playout-delaymode fixed

bearer-cap Speech

!

mgcpfax t38 gateway force

!

dial-peervoice 73 voip

destination-pattern 059[1-8]

sessiontarget ipv4:172.16.1.0.10

dtmf-relayh245-signal

fax-relay ecm disable

fax rate 7200

fax nsf 000000

faxprotocol t38 nse version 0 ls-redundancy 0 hs-redundancy 0 fallback none

!

Does any one have a suggestion here?

Thank you!

Leo

card type e1 1 1

!

network-clock-participate slot 1

!

isdn switch-type primary-qsig

!

voice-card 0

dspfarm

!

voice-card 1

dspfarm

!

voice call send-alert

!

controller E1 1/0

clock source line primary

pri-grouptimeslots 1-31

!

controller E1 1/1

pri-group timeslots 1-31

!

interface Serial1/0:15

noip address

encapsulationhdlc

isdnswitch-type primary-qsig

isdntimer T310 120000

isdnprotocol-emulate network

isdnincoming-voice voice

no cdp enable

!

interface Serial1/1:15

noip address

encapsulationhdlc

isdnswitch-type primary-qsig

isdntimer T310 120000

isdnprotocol-emulate network

isdn incoming-voice voice

no cdp enable

!

voice-port 1/0:15

no non-linear

novad

playout-delaynominal 100

playout-delayfax 100

playout-delaymode fixed

bearer-capSpeech

!

voice-port 1/1:15

no non-linear

novad

playout-delaynominal 100

playout-delayfax 100

playout-delaymode fixed

bearer-cap Speech

!

mgcpfax t38 gateway force

!

dial-peervoice 73 voip

destination-pattern 059[1-8]

sessiontarget ipv4:192.168.0.10

dtmf-relayh245-signal

fax-relay ecm disable

fax rate 7200

fax nsf 000000

faxprotocol t38 nse version 0 ls-redundancy 0 hs-redundancy 0 fallback none

!

1 REPLY
VIP Super Bronze

VoIP FAX Relay issues

Is T.38 configured on both the branch and central router? Since you have configured it on a specific dial-peer instead of globally (voice service voip) have you confirmed that those voip dial-peers are being matched on both routers for the call? When the DSP of one router detects the fact tones it initiates a T.38 switchover; both routers must be configured for this to work.

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