Verizon NCM1100E User Manual page 78

SECURITY & FIREWALL
5.0g/ PORT TRIGGERING
Port triggering can be described as dynamic port forwarding. By setting port
triggering rules, inbound traffic arrives at a specific network host using ports that
are different than those used for outbound traffic. The outbound traffic triggers
the ports where the inbound traffic is directed.
For example, a web server is accessed using UDP protocol on port 2222. The
web server then responds by connecting the user using UDP on port 3333, when
a web session is initiated.
In this case, port triggering must be used since it conflicts with the following
default firewall settings:
• Firewall blocks inbound traffic by default.
• Server replies to your Gateway IP, and the connection is not sent back to the
host since it is not part of a session.
To resolve the conflict, a port triggering entry must be defined, which allows
inbound traffic on UDP port 3333 only after a network host generated traffic to
UDP port 2222. This results in your Gateway accepting the inbound traffic from
the web server and sending it back to the network host which originated the
outgoing traffic to UDP port 2222.
To configure port triggering:
1. From the Advanced
Triggering. Triggering
Advanced menu, select Security & Firewall Security & Firewall and then click Port Port