Configuring IP Addressing
Configuring Network Address Translation
IPC-43
Cisco IOS IP Configuration Guide

Configuring Static Translation

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

Configuring Dynamic Translation

To configure dynamic outside source address translation, use the following commands in global
configuration mode:
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.
See the “Translating Overlapping Address Example” section at the end of this chapter for an example of
translating an overlapping address.
Providing TCP Load Distribution
Another use of NAT is unrelated to Internet addresses. Your organization may have multiple hosts that
must communicate with a heavily used host. Using NAT, you can establish a virtual host on the inside
network that coordinates load sharing among real hosts. DAs that match an access list are replaced with
Command Purpose
Step1 Router(config)# ip nat outside source static
global-ip local-ip
Establishes static translation between an outside local
address and an outside global address.
Step2 Router(config)# interface type number Specifies the inside interface.
Step3 Router(config-if)# ip nat inside Marks the interface as connected to the inside.
Step4 Router(config)# interface type number Specifies the outside interface.
Step5 Router(config-if)# ip nat outside Marks the interface as connected to the outside.
Command Purpose
Step1 Router(config)# ip nat pool name start-ip end-ip
{netmask netmask | prefix-length prefix-length}
Defines a pool of local addresses to be allocated as
needed.
Step2 Router(config)# access-list access-list-number
permit source [source-wildcard]
Defines a standard access list.
Step3 Router(config)# ip nat outside source list
access-list-number pool name
Establishes dynamic outside source translation,
specifying the access list defined in the prior step.
Step4 Router(config)# interface type number Specifies the inside interface.
Step5 Router(config-if)# ip nat inside Marks the interface as connected to the inside.
Step6 Router(config)# interface type number Specifies the outside interface.
Step7 Router(config-if)# ip nat outside Marks the interface as connected to the outside.