Chapter 4 Configuring PPP over ATM with NAT

Configure Network Address Translation

Verify the Configuration

You can verify that the configuration is set the way you want by using the show dsl interface atm command from privileged EXEC mode.

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 ATM 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

 

 

255.255.255.0

 

 

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

 

Example 2:

pool1.

 

Router(config)# ip nat inside source list

For details about this command and additional

 

acl1 pool pool1

parameters that can be set, as well as information

 

 

 

 

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

 

Example:

[FE0–FE3] reside) to be the inside interface for

 

Router(config)# interface vlan 1

NAT.

 

Router(config-if)#

 

 

 

 

Cisco Secure Router 520 Series Software Configuration Guide

 

OL-14210-01

4-7

 

 

 

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Cisco Systems 520 series Permitted by access list acl1 to be translated to, One of the addresses specified in the NAT pool