Hi All,

I've looked through the archives and tried several variations in Google, and I 
haven't found anything on-point... So I'm hoping someone here may be able to 
help this relative Asterisk neophyte shed some light on an issue:

I have a box running Asterisk 1.4.22 in our lab with several Cisco 7961G phones 
and an AEX804E card (4 FXO, hardware echo cancellation).

The server and all phones are on the same subnet (10.2.0.x/255.255.255.0) of 
the local LAN with no NAT, routing, firewall, etc., etc. between the server and 
the phones.

Periodically I'm seeing calls placed from the 7961s through anything on the PBX 
that requires digit entry (the Auto Attendant, Voicemail, etc.) 'randomly' 
drop; extension-to-extension calls extension-to-PSTN, and PSTN-to-extension 
calls never have any issues whatsoever. Nor have I been able to duplicate the 
issues hopping around auto attendants on an inbound PSTN call.

When the call drops, the phone still thinks that it is connected, but the audio 
path is cut off and something similar to the following is dumped to the console

-- <SIP/1103-b71184e0> Playing 'vm-password' (language 'en')
[Oct 28 14:23:07] WARNING[9423]: chan_sip.c:1958 retrans_pkt: Maximum retries 
exceeded on transmission [EMAIL PROTECTED] for seqno 102 (Critical Response) -- 
See doc/sip-retransmit.txt.
[Oct 28 14:23:07] WARNING[9423]: chan_sip.c:1980 retrans_pkt: Hanging up call 
[EMAIL PROTECTED] - no reply to our critical packet (see 
doc/sip-retransmit.txt).

All of the results Google has turned up, and the doc/sip-retransmit.txt file 
point to problems with things in the middle of the path between the server and 
the phone (NAT, firewall, "SIP middle box", proxy) that simply don't exist in 
the configuration that we're using.

I suspect it's an issue with the way the Cisco phones are dealing with DTMF to 
Asterisk or Asterisk dealing with the DTMF from Cisco but that's where I go off 
into unknown territory. (FWIW, until the call drops everything works fine, 
pressing a button triggers the desired action, and audio quality is fantastic)

I've rolled the firmware on the phones up and down with no noticeable change, 
and I also upgraded to Asterisk 1.4.22 version of Asterisk (I had been running 
1.4.21.2, and there are fewer dropped calls with .22 but it's still way too 
often to be acceptable)

Any suggestions are greatly appreciated, but please be explicit... short of 
editing the configuration files and "make install" my Asterisk experience is 
rather limited.

Thanks in advance,

Lincoln

--
Lincoln King-Cliby, CTS
Applications Engineer
ControlWorks Consulting, LLC
http://www.thecontrolworks.com/


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