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Configuring IP Addressing
Configuring Network Address Translation
IPC-46
Cisco IOS IP Configuration Guide
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:
To display translation information, use either of the following commands in EXEC mode:
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.
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.
Command Purpose
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-ip local-ip
[outside local-ip global-ip]
Clears a simple dynamic translation entry containing
an inside translation, or both inside and outside
translation.
Router# clear ip nat translation outside local-ip global-ip
Clears a simple dynamic translation entry containing
an outside translation.
Router# clear ip nat translation protocol inside global-ip
global-port local-ip local-port [outside local-ip local-port
global-ip global-port]
Clears an extended dynamic translation entry.
Command Purpose
Router# show ip nat translations [verbose]
Displays active translations.
Router# show ip nat statistics
Displays translation statistics.