We have a small VOIP network with 10 phone, a dedicated DSL line from Orange/Online and an external Asterisk server in a datacenter. The DSL line is terminated on a Speedtouch modem. With the default settings of the modem we experienced two problems:

• Incoming calls did not get through
• The sound of outgoing calls disappeared while the call was not dropped

In the Asterisk logs we could see the following message:

[Dec 30 13:40:51] WARNING[1911] chan_sip.c: Maximum retries exceeded on transmis
sion 0016c7ea-28120012-73ca27ca-35d5391a@10.0.0.45 for seqno 102 (Critical Respo
nse) -- See doc/sip-retransmit.txt.
[Dec 30 13:40:51] WARNING[1911] chan_sip.c: Hanging up call 0016c7ea-28120012-73
ca27ca-35d5391a@10.0.0.45 - no reply to our critical packet (see doc/sip-retrans
mit.txt).


To fix this, you have to disable the SIP helper on the Speedtouch modem. Connect to the modem with telnet (default ip: 10.0.0.138, default user: Administrator, default password: ) and enter the following commands:

_{Administrator}=>connection
{Administrator}[connection]=>appconfig application=SIP SIP_ALG=disabled
{Administrator}[connection]=>exit