Cisco Systems OL-6426-02 manual Configure Network Address Translation

Chapter 3 Configuring PPP over Ethernet with NAT

Configure Network Address Translation

Configure Network Address Translation

Network Address Translation (NAT) translates packets from addresses that match a standard access list, using global addresses allocated by the dialer interface. Packets that enter the router through the inside interface, packets sourced from the router, or both are checked against the access list for possible address translation. You can configure NAT for either static or dynamic address translations.

Perform these steps to configure the outside Fast Ethernet WAN interface with dynamic NAT, beginning in global configuration mode:

	Command	Purpose
Step 1
	ip nat pool name start-ip end-ip {netmask	Creates pool of global IP addresses for NAT.
	netmask prefix-lengthprefix-length}
	Example:
	Router(config)# ip nat pool pool1
	192.168.1.0 192.168.2.0 netmask 0.0.0.255
	Router(config)#
Step 2
	ip nat inside source {list access-list-number}	Enables dynamic translation of addresses on the
	{interface type number pool name} [overload]	inside interface.
	Example 1:	The first example shows the addresses permitted
		by the access list 1 to be translated to one of the
	Router(config)# ip nat inside source list 1	addresses specified in the dialer interface 0.
	interface dialer 0 overload	The second example shows the addresses
	or	permitted by access list acl1 to be translated to one
		of the addresses specified in the NAT pool pool1.
	Example 2:	For details about this command and additional
	Router(config)# ip nat inside source list	parameters that can be set, as well as information
	acl1 pool pool1	about enabling static translation, see the
		Cisco IOS IP Command Reference, Volume 1 of 4:
		Addressing and Services.
Step 3
	interface type number	Enters configuration mode for the VLAN (on
		which the Fast Ethernet LAN interfaces reside) to
	Example:	be the inside interface for NAT.
	Router(config)# interface vlan 1
	Router(config-if)#
Step 4
	ip nat {inside outside}	Identifies the specified VLAN interface as the
		NAT inside interface.
	Example:	For details about this command and additional
	Router(config-if)# ip nat inside	parameters that can be set, as well as information
	Router(config-if)#	about enabling static translation, see the
		Cisco IOS IP Command Reference, Volume 1 of 4:
		Addressing and Services.

Cisco 1800 Series Integrated Services Routers (Fixed) Software Configuration Guide

OL-6426-02 3-7