Incoming IAX call failed - Callee number is empty


when we send an IAX call from another asterisk the callee number is not found as Mobydick expect a SIP call and read the SIP Header. Here are logs:

   -- Executing [805@mdc_incoming-4:1] Set("IAX2/allUsers-11181", "MDC_CALLER_NUM_TRUNK=805") in new stack
[Mar 15 13:37:54] WARNING[26227][C-0000001c]: chan_sip.c:21873 func_header_read: This function can only be used on SIP channels.
    -- Executing [805@mdc_incoming-4:2] Gosub("IAX2/allUsers-11181", "sub_deterdest,s,1(TMP_TO_HEADER, )") in new stack
    -- Executing [s@sub_deterdest:1] Verbose("IAX2/allUsers-11181", "1,sub_deterdest:: variable: TMP_TO_HEADER header:  ") in new stack
 sub_deterdest:: variable: TMP_TO_HEADER header:  
    -- Executing [s@sub_deterdest:2] Set("IAX2/allUsers-11181", "TMP_DN=") in new stack
    -- Executing [s@sub_deterdest:3] Set("IAX2/allUsers-11181", "TMP_DN=") in new stack
    -- Executing [s@sub_deterdest:4] Set("IAX2/allUsers-11181", "TMP_TO_HEADER=") in new stack
    -- Executing [s@sub_deterdest:5] Return("IAX2/allUsers-11181", "") in new stack
    -- Executing [805@mdc_incoming-4:3] Verbose("IAX2/allUsers-11181", "1,to-header  is extracted") in new stack
 to-header  is extracted

Caller 805 from another asterisk is calling extension 805 from Mobydick. As you see TMP_TO_HEADER is empty ! Call is ended with

[Mar 15 13:37:54] WARNING[26227][C-0000001c]: pbx.c:6643 __ast_pbx_run: Channel 'IAX2/allUsers-11181' sent to invalid extension but no invalid handler: context,exten,priority=mdc_mapping-2,s,1
    -- Hungup 'IAX2/allUsers-11181'

Hi @tootai,

a bit unrelated, but are you required to use IAX? We usually prefer to use SIP.



with IAX we save a lot of firewall and other networks problems. Usually we send calls using IAX or SIP with IAX as failover eg CHANUNAVAIL or CONGESTION.


Hi Daniel,

do both asterisk appliances use the same Version? IAX2 is not well maintained and despite that often not working smooth between different asterisk versions.
As a result, not much of our members spend a lot time with it. You can try to change “Number
Determination” in the account, but I guess you have to bring the oposite side to represent number in the To-Header (or whatever equivalent iax2 uses here).

Best regards,

Hi Steve,

our Asterisk are today mainly v13 or v15 but since 1.4 we never had any problem with IAX interconnexion. We work with stock Asterisk as well as with Elastix/Xivo/Wazo and never had any trouble to setup IAX.

Anyway, now we know that Mobydick is not IAX friendly, we will continue to discover it.

Thanks for your feedback


Hi Daniel,

I would not say mobydick/pascom is not IAX friendly, but I agree that I am not (and maybe Jan :wink: ).
Maybe a colleague of us could help you, let’s wait.
Just for my interest, your IAX interconnexions also work well between new and old asterisk Versions? For example between v13 and v11.6?


Yes, for our mobydick test purpose our test Asterisk is 13.19.2 and IAX is working well apart of the incoming calls. We have few users connected with 11.19.0 without problem.

Hi guys,

is your problem with the empty To-Header still exists?
You can try to change the “number determination” within the trunk account configuration to “Request-URI” - pascom which is receiving the fax


Hi Markus,

\o/ EXCELLENT, with “Request-URI” it work !

Many thanks