Cisco Systems 78-11741-02 manual Configuring Static Translation, IPC-38

Configuring IP Addressing

Configuring Network Address Translation

Host 1.1.1.1 receives the packet and continues the conversation. The router performs Steps 2 through 5 for each packet.

Configuring Static Translation

To configure static inside source address translation, use the following commands in global configuration mode:

	Command	Purpose
Step 1
	Router(config)# ip nat inside source static local-ip	Establishes static translation between an inside local
	global-ip	address and an inside global address.
Step 2
	Router(config)# interface type number	Specifies the inside interface and enters interface
		configuration mode.
Step 3
	Router(config-if)# ip nat inside	Marks the interface as connected to the inside.
Step 4
	Router(config)# interface type number	Specifies the outside interface and enters interface
		configuration mode.
Step 5
	Router(config-if)# ip nat outside	Marks the interface as connected to the outside.

The previous steps are the minimum you must configure. You could also configure multiple inside and outside interfaces.

Configuring Dynamic Translation with an Access List

To configure dynamic inside source address translation with an access list, use the following commands in global configuration mode:

	Command		Purpose
Step 1
	Router(config)# ip	nat pool name start-ip end-ip	Defines a pool of global addresses to be allocated as
	{netmask netmask	prefix-length prefix-length}	needed.
Step 2
	Router(config)# access-listaccess-list-number		Defines a standard access list permitting those
	permit source [source-wildcard]		addresses that are to be translated.
Step 3
	Router(config)# ip	nat inside source list	Establishes dynamic source translation, specifying
	access-list-number	pool name	the access list defined in the prior step.
Step 4
	Router(config)# interface type number		Specifies the inside interface and enters interface
			configuration mode.
Step 5
	Router(config-if)#	ip nat inside	Marks the interface as connected to the inside.
Step 6
	Router(config)# interface type number		Specifies the outside interface and enters interface
			configuration mode.
Step 7
	Router(config-if)#	ip nat outside	Marks the interface as connected to the outside.

Note The access list must permit only those addresses that are to be translated. (Remember that there is an implicit “deny all” at the end of each access list.) An access list that is too permissive can lead to unpredictable results.

Cisco IOS IP Configuration Guide

IPC-38