Cisco Systems 78-11741-02 manual Monitoring and Maintaining NAT, IPC-46

Configuring IP Addressing

Configuring Network Address Translation

Command	Purpose
Router(config)# ip nat translation icmp-timeout seconds	Changes the ICMP timeout value from 1 minute.
Router(config)# ip nat translation syn-timeout seconds	Changes the Synchronous (SYN) timeout value from
	1 minute.

Monitoring and Maintaining NAT

By default, dynamic address translations will time out from the NAT translation table at some point. To clear the entries before the timeout, use the following commands in EXEC mode as needed:

Command	Purpose
Router# clear ip nat translation *	Clears all dynamic address translation entries from
	the NAT translation table.
Router# clear ip nat translation inside global-iplocal-ip	Clears a simple dynamic translation entry containing
[outside local-ip global-ip]	an inside translation, or both inside and outside
	translation.
Router# clear ip nat translation outside local-ipglobal-ip	Clears a simple dynamic translation entry containing
	an outside translation.
Router# clear ip nat translation protocol inside global-ip	Clears an extended dynamic translation entry.
global-port local-ip local-port [outside local-ip local-port
global-ip global-port]

To display translation information, use either of the following commands in EXEC mode:

Command		Purpose
Router#	show ip nat translations [verbose]	Displays active translations.
Router#	show ip nat statistics	Displays translation statistics.

Deploying NAT Between an IP Phone and Cisco CallManager

Cisco IP phones use the Selsius Skinny Station Protocol to connect with and register to the Cisco CallManager (CCM). Messages flow back and forth that include IP address and port information used to identify other IP phone users with which a call can be placed.

To be able to deploy Cisco IOS NAT between the IP phone and CCM in a scalable environment, NAT needs to be able to detect the Selsius Skinny Station Protocol and understand the information passed within the messages.

When an IP phone attempts to connect to the CCM and it matches the configured NAT translation rules, NAT will translate the original source IP address and replace it with one from the configured pool. This new address will be reflected in the CCM and be visible to other IP phone users.

Cisco IOS IP Configuration Guide

IPC-46