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Fax Over IP on my cisco 1760

Posted on 2003-11-25
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Last Modified: 2007-12-19
I have a cisco 1760 with 4 port FXS/DID card in it. I hooked a fax machine to one of the ports and configured a dial-peer for fax. Im sending the calls through a cable modem (Time Warner Cable) to my CO where the call gets terminated. Im having trouble sending faxes as well as recieving. It does go through about 50% of the time, but the other 50% the fax send/recieve fails and it says I had a communication error on the line. All the fax machines im sending to are on a PSTN line (verizon,ATT,...). I want to know if there is something Im missing in my config or what the story is. Here is how I have it setup

Cisco 1760 w/fax machine connected to FXS port:
dial-peer voice XXX voip
 description Outgoing FAX
 destination-pattern ####..........
 session target ipv4:X.X.X.X
 playout-delay maximum 1700
 playout-delay nominal 1500
 playout-delay fax 700
 playout-delay minimum high
 playout-delay mode fixed no-timestamps
 fax-relay ecm disable
 fax protocol t38 ls-redundancy 0 hs-redundancy 0 fallback pass-through g711ulaw
 no vad  

Cisco 5850 in my CO:
dial-peer voice XXXX pots
 description FAX
 answer-address ########
 destination-pattern ####..........
 translate-outgoing called XXX
 direct-inward-dial
 port X/X:X

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Question by:Rich27
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by:MaxQ
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So your fax calls are traversing the public Internet between the two routers?  Are you doing any QoS on the routers now?  My first guess would be that the calls are getting enough delay/jitter that it's confusing the fax machines and causing them to drop the call.  Do voice calls over this link have any audible artifacts?
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by:Rich27
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theres static but its not bad, for the most part the voice calls are pretty good
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by:MaxQ
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Okay...but I'm wondering if a fax call, being encoded data, might not be more sensitive to such things than the human ear is.  Although they have error correction, I wonder if jitter especially would be hard for them to deal with.  Can you set the baud rate way down on the fax machines for a bit just to see if it improves the reliability at all?
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by:Rich27
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yeah what should i set it to?
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by:sheahmed
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you are missing a command in dial-peer mode ...

fax rate 9600 ... or whatever ...

i m using FAXoIP on a quite slower media ... and its working fine ... with the config given below ...
!
dial-peer voice 111 voip
 destination pattern 111
 session target ipv4:10.1.1.1
 codec g729r8 bytes 90
 no vad
 fax rate 9600
 fax prot t38
!
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by:Rich27
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sheahmed,

are you sending the fax across the public internet ?
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by:Rich27
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Also Im trying to send to other fax machines that are not using Fax over IP. they are on the PSTN
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by:sheahmed
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no ... but my media is quit slower and jittery ...
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by:sheahmed
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try to send the fax using a plain voip dial-peer without any additional fax config ... it should work ...

i m sending fax towards pstn, from the dial-peers which are not configured for fax ...
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by:Rich27
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I tried sending over a regular voip dial-peer and it did not work for me
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by:Rich27
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also I cannot recieve fax at all. I see the fax try to start recieving but it always fails
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sheahmed earned 200 total points
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u are able to hear the negotiation voice? whats the standard of your fax machine? machine supports t38?
try dialing after enabling debugging ...
and examine the reason of break up ... this is the only way to troubleshoot ... if you are satisfied with the config ...
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