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Chapter 19 ALG
ZyWALL USG 50 User’s Guide
338
can receive incoming calls from the Internet, LAN IP addresses B and C can still
make calls out to the Internet.
Figure 202 VoIP Calls from the WAN with Multiple Outgoing Calls
VoIP with Multiple WAN IP Addresses
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
1 and calls from LAN IP address
B go out through WAN IP address 2.
Figure 203 VoIP with Multiple WAN IP Addresses
Finding Out More
• See Section 6.5.12 on page 100 for related information on these screens.
• See Section 7.9 on page 139 for a tutorial showing how to use the ALG for peer-
to-peer H.323 traffic.
• See Section 7.11 on page 146 for an example of making an IPPBX using SIP or
a SIP server in the DMZ zone accessible from the Internet (the WAN zone).