ZyXEL Communications 1000 Manual De Usuario

Chapter 21 ALG

ZyWALL USG 1000 User’s Guide

can receive incoming calls from the Internet, LAN IP addresses B and C can still 
make calls out to the Internet. 

Figure 301   VoIP Calls from the WAN with Multiple Outgoing Calls

With multiple WAN IP addresses on the ZyWALL, you can configure different 
firewall and NAT (port forwarding) rules to allow incoming calls from each WAN IP 
address to go to a specific IP address on the LAN (or DMZ). Use policy routing to 
have the H.323 (or SIP) calls from each of those LAN or DMZ IP addresses go out 
through the same WAN IP address that calls come in on. The policy routing lets 
the ZyWALL correctly forward the return traffic for the calls initiated from the LAN 
IP addresses.

For example, you configure firewall and NAT rules to allow LAN IP address A to 
receive calls through public WAN IP address 1. You configure different firewall and 
port forwarding rules to allow LAN IP address B to receive calls through public 
WAN IP address 2. You configure corresponding policy routes to have calls from 
LAN IP address A go out through WAN IP address 

 and calls from LAN IP address 

B go out through WAN IP address 2. 

Figure 302   VoIP with Multiple WAN IP Addresses

• See 

 for related information on these screens.

• See 

 for a tutorial showing how to use the ALG for 

peer-to-peer H.323 traffic. 

• See 

 for an example of making an IPPBX using SIP or 

a SIP server in the DMZ zone accessible from the Internet (the WAN zone).