3Com Switch 8800 Family Firewall Module Configuration and Command Reference Guide

82 CHAPTER 6: NAT CONFIGURATION

their destination addresses and port numbers and forward the response packets to

the corresponding internal hosts.

Static Network Address

Translation

This new static NAT approach converts the internal host addresses in a specified

range to the specified public network addresses (only the network part is

converted and the host part is unchanged). When internal hosts access the outside

network, their internal addresses are converted to public network addresses if

their internal addresses are in the specified range. Accordingly, outside hosts can

use the public network address to access directly internal hosts if the internal host

addresses which are converted from the public network addresses are in the

specified range.

Static NAT function creates direct mapping between internal host addresses and

public network addresses, and implement the function similar to NAT server.

However, static NAT function requires a large IP address space since it holds the

one-to-one mapping between internal host addresses and public network

addresses. You can combine the static and dynamic NAT function, as long as the

addresses are not in conflict.

NAT Configuration NAT configuration includes:

■ Configure address pool.

■ Configure Easy IP

■ Configure static NAT

■ Configure many-to-many NAT

■ Configure NAPT

■ Configure internal server support

■ Configure NAT effective time (Optional)

Configuring Address

Pool

The address pool is a collection of some consecutive IP addresses, while internal

data packet needs to access external network via NAT, a certain address in the

address pool will be chosen as the source address. Perform the following

configurations in the system view.

CAUTION: An address pool is irremovable while this address pool has set up the

association with a certain access control list for NAT.

If Easy IP is the one and only function supported by the security gateway, the

address of the interface will be used plainly as the translated IP address, no NAT

pool needed.

Tabl e 70 Configure address pool

Operation Command

Define an address pool nat address-group group-number start-addr end-addr

Delete an address pool undo nat address-group group-number