M2M IDG500AM-0T001 User Manual page 102

M2M Cellular Gateway
Scenario Application Timing
When a SIP phone is behind a NAT gateway, and it is expected to make a call to or
receive a call from the Internet. The "SIP ALG" feature must be activated in the NAT
gateway.
Scenario Description
The "SIP ALG" feature in the NAT Gateway is enabled to monitor, open up ports and
make the address and port translation for the voice communication of the SIP phone
behind the gateway.
A SIP phone behind a NAT gateway can call another SIP phone with the help of the SIP
server in the Internet.
Parameter Setup Example
Following table lists the parameter configuration for the NAT gateway in above diagram.
Configuration Path
ALG
Scenario Operation Procedure
In above diagram, the NAT Gateway is the gateway of Network‐A and the subnet of its
Intranet is 10.0.75.0/24. The gateway has the IP address of 10.0.75.2 for LAN interface
and 118.18.81.33 for WAN interface. It serves as a NAT router.
Configure the NAT gateway with SIP ALG being enabled.
When the SIP Phone #1 behind the NAT gateway has booted up, it will register to the
SIP server in the Internet. So, the SIP server knows where the SIP Phone #1 is. In the
same way, the SIP Phone #2 also registers to the SIP server.
Index skipping is used to reserve slots for new function insertion, when required.
[Special AP & ALG]-[Configuration]
SIP ALG ■ Enable
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