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Strange Fax Issue

I have a translation pattern xlat'ing a DID # to an external fax # with the called party transform mask set to 9xxxxxxxxxx (local # so no preceding 1 is necessary). Doubt it matters but the fax machine is in the same physical location as the gateway, but the cucm cluster is remote. The fax line is a POTS plugged directly into the fax machine.

Anyways, they just started experiencing an issue where they can make outbound faxes fine. Inbound faxes look okay but are not completing. They see the fax machine pick up the incoming call but the sending fax reports a failed send. The fax machine has an attached handset and 2 way calls are fine in both directions. It's just incoming faxes that don't work when people fax to the DID translated to the external fax #.

There are actually 2 DID translations to 2 fax lines with this same setup and they replaced 1 of the fax machines so it's not a physical fax machine issue. The 2 POTS lines are each with a different carrier, so it's not a carrier issue.

Any ideas on how to troubleshoot this will be much appreciated.

thanks,

Will

1 ACCEPTED SOLUTION

Accepted Solutions

Re: Strange Fax Issue

Hi Will,

Most common problems for faxes failing:

-Slips on your T1's (show controllers t1, use network-clock-select 1 t1 0/0/0 if slips)

-packet loss ('show call active voice brief | i lost' should show 0/0/0 for all calls

-your configuration isn't correct. I suggest this for all non-mgcp gateways:

voice service voip

fax protocol none

modem passthrough nse codec g711ulaw

hth,

nick

3 REPLIES

Re: Strange Fax Issue

Hi Will,

Most common problems for faxes failing:

-Slips on your T1's (show controllers t1, use network-clock-select 1 t1 0/0/0 if slips)

-packet loss ('show call active voice brief | i lost' should show 0/0/0 for all calls

-your configuration isn't correct. I suggest this for all non-mgcp gateways:

voice service voip

fax protocol none

modem passthrough nse codec g711ulaw

hth,

nick

Silver

Re: Strange Fax Issue

That's good stuff Nick. Thanks for the info. The faxes are coming in via the 2 POTS lines rather than a PRI though. I don't have those 2 statements within the voice service voip section.

It turns out that it was setup this way because this branch didn't have any analog gateways. A 2 port FXO and 4 port FXS module have been installed since. I took the opportunity to config the FXO and FXS ports and had a guy on site make the cabling changes. He had to build a couple of cables for the demarc extension but only had a coax crimper so as soon as he gets that fixed and I can finish testing I'll let you know how it goes. He was able to test with an analog phone plugged directly into the ISR though and it tested good. I can also see the FXO ports pick up on inbound calls and see the FXS ports go off-hook when the calls are transferred.

I think this is a less-kludgy setup anyways, but I'll input those 2 statements as well during the next downtime window after I research them a bit more.

thanks Nick,

Will

Silver

Re: Strange Fax Issue

Well, the tech onsite reterm'd the cables and it seemed like everything was working. I got fax tone when I called but test faxes wouldn't go through.

I copy/pasted the 2 statements you gave me under voice service voip and it fixed the issue completely.

I'm still not sure why this stopped working suddenly when this has been setup for a couple of years from what I've been told.

thanks for your help,

Will

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