
ICR-1601
98
As shown in the diagram, the calling
starts from the SIP Phone #1 to the SIP
server via the NAT gateway. Then the
SIP server invites the SIP Phone #2
and finally, the SIP Phone #1 talks to
the SIP Phone #2. But for the NAT
gateway, SIP Phone #2 is an unknown
host, so the active access from the
Phone #2 will be treated as
unexpected traffic and will be blocked
out. With the SIP ALG function
enabled, the NAT gateway will
monitor the control traffic for the SIP
calls, and recognized the traffic from
SIP Phone #2 is part of the connection
sessions with SIP Phone #1.
Special AP & ALG Setting
Go to Basic Network > Port Forwarding > Special AP & ALG tab.
The Special AP setting allows some applications require multiple connections. The ALG setting allows
user to Support some SIP ALG, like STUN.
Enable Special AP & ALG
Configuration
Item
Value setting
Description
Special AP
The box is checked by
default
Check the Enable box to activate the Special AP function.
ALG Enable
The box is checked by
default
Check the Enable box to activate the SIP ALG function.
Save
N/A
Click the Save button to save the settings.
Undo
N/A
Click the Undo button to cancel the settings