User's Guide

Chapter 10 WAN
EMG3435-Q20A User’s Guide
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ALG O ve rvie w
Application Layer Gateway (ALG) allows the following applications to operate properly through the
EMG3435-Q20A’s NAT.
• SIP - Session Initiation Protocol (SIP) - An application-layer protocol that can be used to create voice
and multimedia sessions over Internet.
• H.323 - A teleconferencing protocol suite that provides audio, data and video conferencing.
• FTP - File Transfer Protocol - an Internet file transfer service.
• SNMP - Simple Network Management Protocol - An application-layer protocol that can be used to
exchange management information between network devices.
• RTSP - Real Time Streaming Protocol - An application-layer protocol that can be used to stop, pause
or play video and audio applications streaming on the Internet.
• IRC - Internet Relay Chat - An application-layer protocol that can control the relay chat applications
and allow clients to have real-time communications with others on the Internet.
The ALG feature is only needed for traffic that goes through the EMG3435-Q20A’s NAT.
To change your EMG3435-Q20A’s ALGs and VPN pass-through settings, click Expe rt Mo de > WAN > NAT
> Pa ssthroug h. The screen appears as shown.
Fig ure 60 Expert Mode > WAN > NAT > Passthrough
The following table describes the labels in this screen.
Table 24 Expert Mode > WAN > NAT > Passthrough
LABEL DESC RIPTIO N
ALG Setup
FTP Select Ena ble to allow TCP packets with a specified port destination to pass through.
H.323 Select Ena ble to allow peer-to-peer H.323 calls.
SIP Select Ena ble to make sure SIP (VoIP) works correctly with port-forwarding and address-
mapping rules.
SNMP Select Ena ble to allow a manager station to manage and monitor the EMG3435-Q20A
through the network via SNMP.