Cisco 1801, Configuration Manual

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Cisco 1800 Series Integrated Services Routers (Fixed) Software Configuration Guide
OL-6426-02
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
netmask | prefix-length prefix-length }
Example:
Router(config)# ip nat pool pool1
192.168.1.0 192.168.2.0 netmask 0.0.0.255
Router(config)#
Creates pool of global IP addresses for NAT.
Step 2 ip nat inside source { list access-list-number }
{ interface type number | pool name } [ overload ]
Example 1:
Router(config)# ip nat inside source list 1
interface dialer 0 overload
or
Example 2:
Router(config)# ip nat inside source list
acl1 pool pool1
Enables dynamic translation of addresses on the
inside interface.
The first example shows the addresses permitted
by the access list
1 to be translated to one of the
addresses specified in the dialer interface 0 .
The second example shows the addresses
permitted by access list
acl1 to be translated to one
of the addresses specified in the NAT pool pool1 .
For details about this command and additional
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
Example:
Router(config)# interface vlan 1
Router(config-if)#
Enters configuration mode for the VLAN (on
which the Fast Ethernet LAN interfaces reside) to
be the inside interface for NAT.
Step 4
ip nat { inside | outside }
Example:
Router(config-if)# ip nat inside
Router(config-if)#
Identifies the specified VLAN interface as the
NAT inside interface.
For details about this command and additional
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
.