3Com Switch 8800 Advanced Software V5 Configuration Guide

990 CHAPTER 76: NAT CONFIGURATION
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■ The addresses in the address pool referenced by NAT must be different from
the interface address. Otherwise, the service can be implemented. To use the
interface address as the translation address, Easy IP must be used.
Configuring Address
Translation
Introduction to Address
Translation
Address translation is implemented by associating an ACL with an address pool (or
an interface address in case of Easy IP). This association specifies what packets
(defined by ACLs) can use which address (one in the address pool, or the interface
address itself) to access the external network. When an internal host needs to
send data packets to an external network, the NAT gateway checks the first
packet against the ACL to see if it is permitted. If so, NAT chooses an address from
the address pool (or the interface address, depending on the association) to
perform address translation. This address mapping is recorded in an address
translation table so that subsequent packets can be translated directly according
to this mapping entry.
For details about ACL, refer to “ACL Overview” on page 801.
The configuration for different forms of address translation varies somewhat:
■ Easy IP
This feature is implemented using the nat outbound acl-number command,
without the address-group keyword specified. When address translation, the
NAT gateway directly uses an interface’s public IP address as the translated IP
address, and uses ACLs to restrict the traffic.
■ Many-to-many NAT
You only need to associate an ACL with an address pool, without considering port
numbers.
■ NAPT
You need to associate an ACL with an address pool, and deal with both IP
addresses and port numbers.
■ NAT multiple-instance
You need to configure vpn instance vpn-instance-name in the rule of an ACL to
specify the MPLS VPN users that need address translation and add a static route to
the public network into the routing table of the private network. NAT
multiple-instance is supported on Easy IP, Many-to-many NAT, and NAPT.
Configuring Address
Translation
Configuring Easy IP
Follow these steps to configure Easy IP:
To do... Use the command... Remarks
Enter system view system-view -