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Chapter 2: Advanced Setup Options 21
2.4 NAT Firewall
The X5’s built-in NAT (Network Address Translation) firewall
provides a good level of protection from unauthorized access.
NAT keeps private a network’s internal IP addresses and presents
to the Internet one public IP address. With NAT, only one LAN
user can use the public IP address. NAT’s more robust
counterpart, NAPT (Network Address Port Translation), allows
specified LAN users to share the one public IP address. Both
NAPT and NAT are transparent to end users.
Your X5’s NAT firewall is enabled by default; the default setting is
dynamic NAPT—everything is automatic. With dynamic NAPT,
anyone can use the public IP address (that is, the modem’s WAN
IP address). You shouldn’t need to change this setting. However, if
your service provider instructs you to disable it (or change it), go to
the Advanced Setup page and click the NAT button.
NAT Default is dynamic NAPT. Options are NAPT, NAT,
and Disable. You should not need to change this
setting, unless advised to do so by your provider.
Warning: If you select Disable, all your modem’s
firewall capabilities are turned off.
Session Name
Only applicable to NAT and NAPT; user-definable
name to differentiate between different NAT
sessions, different PPP sessions, and different
PVCs.
User’s IP IP address of the client computer you want to add.
Action
Choices are Add or Delete.