ZyXEL Communications Prestige 2602R Series, User Manual

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Prestige 2602R Series User’s Guide
Appendix F SIP Passthrough 393
A
P P E N D I X
F
SIP Passthrough
Enabling/Disabling the SIP ALG
You can turn off the Prestige SIP ALG to avoid retranslating the IP address of an existing SIP
device that is using STUN. If you want to use STUN with a SIP client device (a SIP phone or
IP phone for example) behind the Prestige, use the
ip alg disable ALG_SIP
command
to turn off the SIP ALG.
Signaling Session Timeout
Most SIP clients have an “expire” mechanism indicating the lifetime of signaling sessions.
The SIP UA sends registration packets to the SIP server periodically and keeps the session
alive in the Prestige.
If the SIP client does not have this mechanism and makes no call during the Prestige SIP
timeout default (60 minutes), the Prestige SIP ALG drops any incoming calls after the timeout
period. You can use the
ip alg siptimeout
command to change the timeout value.
Audio Session Timeout
If no voice packets go through the SIP ALG before the timeout period default (5 minutes)
expires, the SIP ALG does not drop the call but blocks all voice traffic and deletes the audio
session. You cannot hear anything and you will need to make a new call to continue your
conversation.