[cisco-voip] fax configuration

[Daniel Pagan]

There’s not enough information here, but the first question that comes to mind is related to fax protocols - what is this Elastix server configured to use and what does it support? I would expect it to support protocol-based T38, but the IOS excerpt below shows your router is configured for protocol-based pass through. If Elastix supports protocol T38 then change either the global fax configuration or dial-peer fax configuration to “fax protocol t38 fallback none”.

Another question to answer is whether or not this Elastix server configured to support SIP over UDP since the default transport seems to be in use on the router.

For faxes to this server, are you sure the outgoing dial-peer in use is dial-peer 1? Is dial-peer 2 being used as the incoming dial-peer for faxes to Elastix? If so then what fax protocols and switchover method is configured on that remote side?

Also, the debug information below isn’t very helpful - do you have a full output of SIP message and voip dial-peer debugs from a failed fax attempt? This is going to be a requirement for anyone to troubleshoot this type of issue. You’ll need to determine if the terminating gateway (in this case the fax server) is transmitting the appropriate protocol messages for initiating the switchover. If it is initiating switchover, you’ll need to determine what this router is doing with the switchover request. There’s a good chance these fax attempts don’t even get to the point of switchover, and that it’s never even getting a successful SIP dialog to begin with.

At its most fundamental level, can you test if a standard *voice* call to this server works? Standard operations is that a voice call is setup first, and then fax negotiation is started only once the voice call is established regardless if you’re doing NSE or protocol based switchover.

Some more info…
Stay away from NSE switchover to Elastix since this is Cisco proprietary and will not work with this server.
If you end up using T38, a helpful command to use will be “debug fax relay t30 all”. This debug will show you low-speed fax tones only, but is still very helpful for troubleshooting T38 faxing.
I’ve taken the section below from an internal document I put together for FoIP:

-- debug fax relay t30 all --
This debug will display the detected and transmitted low-speed tones.
This debug only applies to T38 fax relay – it will show no output when using passthrough.

Successful T38 fax transmission captured in a debug fax relay t30 all on a VG202 OGW. Comments in <> will not be displayed in actual debug output.
<CED>
<CNG>
<Detection of DIS – switchover to T38>
timestamp=6560534 fr-msg-tx NSF
timestamp=6560984 fr-msg-tx DIS
timestamp=6562834 fr-msg-det DCS
<High speed training check>
timestamp=6568294 fr-msg-tx CFR
<High speed page transmission>
timestamp=6613044 fr-msg-det EOP
timestamp=6615494 fr-msg-tx MCF
timestamp=6617094 fr-msg-det DCN
<Disconnect/On-hook>

NOTE: The output for “debug fax relay t30 all” doesn’t indicate direction of received or transmitted fax relay tones. When
reviewing the output, you’ll need to remember the DIS comes from the called fax, DCS from calling fax, etc. Keeping this in
mind will help you review and understand the direction of each  demodulated fax tone sent and received via fax relay
protocols.

Additional information would be needed to troubleshoot this but hopefully this helps.

- Daniel

From: cisco-voip [mailto:cisco-voip-bounces at puck.nether.net] On Behalf Of samaneh ebrahimi
Sent: Thursday, May 07, 2015 4:26 PM
To: cisco-voip at puck.nether.net
Subject: [cisco-voip] fax configuration

Hi  ,
 I want send virtual fax from zoiper1 and receive it on zoiper2.
I used Elastix on scenario , create IAX2 extension on Elastix  , trunk sip for connectivity to cisco gateway and Outbound route for sip-trunk and Inbound-route for connect external call to local  IAX2 extension. this configure is for both Elastix.

R1/R2

!
voice service voip
all-connection sip to sip
fax protocol path-throat g711alaw
!
dial-pper voice 1 voip
description connectivity to Elastix
destination-pattern xx
session target ipv4: elastix-ip
session protocol sip
codec g711alaw
!
dial-pper voice 2 voip
destination-pattern xx
session target ipv4: R1/R2-ip
session protocol sip
codec g711alaw
!

when call , by enable debug ccsip error give this message : bad URL ... or by debug ccsip call , last line : cause code 200 .
and fax not send .

I think Elastix don't have true configuration for fax.
scenario attacked. please help me to resole problem .
Thank you.
Have a good time.
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