ZyXEL Communications NXC5200 User Manual page 549

The NXC routes and applies SNAT for traffic from some interfaces but not from
others.
The NXC automatically uses SNAT for traffic it routes from internal interfaces to
external interfaces. For example LAN to WAN traffic. You must manually configure
a policy route to add routing and SNAT settings for an interface with the
Interface Type set to General. You can also configure a policy route to override
the default routing and SNAT behavior for an interface with the Interface Type
set to Internal or External.
The NXC is not applying a policy route's port triggering settings.
You also need to create a firewall rule to allow an incoming service.
I cannot get the application patrol to manage SIP traffic.
Make sure you have the SIP ALG enabled.
I cannot get the application patrol to manage H.323 traffic.
Make sure you have the H.323 ALG enabled.
I cannot get the application patrol to manage FTP traffic.
Make sure you have the FTP ALG enabled.
The NXC keeps resetting the connection.
If an alternate gateway on the LAN has an IP address in the same subnet as the
NXC's LAN IP address, return traffic may not go through the NXC. This is called an
asymmetrical or "triangle" route. This causes the NXC to reset the connection, as
the connection has not been acknowledged.
NXC5200 User's Guide
Chapter 39 Troubleshooting
549