IP Addressing: NAT Configuration Guide, Cisco IOS Release 12.4T
FPG Endpoint Agnostic Port Allocation
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FPG Endpoint Agnostic Port Allocation

FPG Endpoint Agnostic Port Allocation

Last Updated: December 18, 2011

When the Endpoint Agnostic Port Allocation feature is configured, an entry is added to the Symmetric Port Database. If the entry is already available, the port listed in the Symmetric Port Database is used and the packet is sent. This feature is only required if you need to configure NAT with pool overload or interface overload. Endpoint Agnostic Port Allocation is also known as Symmetric Port Allocation.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest feature information and caveats, see the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the Feature Information Table at the end of this document.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Information About Endpoint Agnostic Port Allocation

When a packet is being transmitted, the Symmetric Port Database is checked to see if the requested port is already allocated. If it has been allocated, it is checked if the source computer entry in the database matches the computer requesting the port. If this is true, the port listed in the Symmetric Port Database is used and the packet is sent.

If the computers do not match or if the requested port is not in the Symmetric Port Database, the feature continues checks to the NAT Port database for an entry matching the requested port. If no entry is found, this means that the port is available. A new entry is added to the NAT Port database, and to the existing NAT database, allocating the port to the requesting computer, and the packet is sent.

If no matching entry in the NAT Port database is found, it means that the port is busy, or otherwise unavailable. The next available port is found, which is allocated to the requesting computer. An entry is added to the NAT Port database with the requesting computer and the available port. An entry is added to the Symmetric Port database, with the requesting computer, the allocated port and the requested port and the packet is sent.

This feature is only required if you need to configure NAT with pool overload or interface overload. This feature is not applicable for other NAT configurations.

How to Configure Endpoint Agnostic Port Allocation

Configuring Endpoint Agnostic Port Allocation

Perform this task to configure NAT to support the Endpoint Agnostic Port Allocation feature.


Note


This feature must be enabled by the user. It should be enabled before NAT is enabled. If it is enabled later, it will not translate the previously established connection. When this feature is disabled, it will not be seen in the output of the show running-configcommand.

>
SUMMARY STEPS

1.    enable

2.    configure terminal

3.    interface interface name

4.    ip nat inside

5.    exit

6.    access list 1 permit ip address mask

7.    ip nat inside source list 1 interface interface name

8.    ip nat service enable-sym-port

9.    exit


DETAILED STEPS
  Command or Action Purpose
Step 1
enable


Example:

Router> enable

 

Enables privileged EXEC mode.

  • Enter your password if prompted.
 
Step 2
configure terminal


Example:

Router# configure terminal

 

Enters global configuration mode.

 
Step 3
interface interface name


Example:

Router (config)# interface Ethernet 0/0

 

Configures the Ethernet 0/0 interface.

 
Step 4
ip nat inside


Example:

Router (config-if)# ip nat inside

 

Enables Network Address Translation (NAT) for the inside address.

 
Step 5
exit


Example:

Router (config-if)# exit

 

Exits interface configuration mode.

 
Step 6
access list 1 permit ip address mask


Example:

Router (config)# access list 1 permit 172.18.192.0.0.0.0.255

 

Creates an access list called 1.

 
Step 7
ip nat inside source list 1 interface interface name


Example:

Router (config)# ip nat inside source list 1 interface Ethernet 0/0

 

Enables NAT for the inside source for access list 1 which is attached to the Ethernet interface.

 
Step 8
ip nat service enable-sym-port


Example:

Router (config)# ip nat service enable-sym-port

 

Enables the symmetric port allocation.

 
Step 9
exit


Example:

Router(config)# exit

 

Exits global configuration mode.

 

Verifying Endpoint Agnostic Port Support

To verify the Endpoint Agnostic Port Support feature, use the following command.

SUMMARY STEPS

1.    show ip nat translations


DETAILED STEPS
show ip nat translations



Example:
Router# show ip nat translations
 
NAT Symmetric Port Database: 1 entries
public ipaddr:port [tableid] | port# [refcount][syscount] | localaddr:localport [flags]
172.18.192.69:1024 [0] | 1025 [1] [0] | 172.18.192.69:1024 [0]

Configuration Examples for Endpoint Agnostic Port Allocation

Configuring Endpoint Allocation Example

interface Ethernet0/0
	ip nat inside
	exit
access list 1 permit 172.18.192.0.0.0.255
ip nat inside source list 1 interface Ethernet0/0
ip nat service enable-sym-port
end

Additional References

Related Documents

Related Topic

Document Title

NAT configuration tasks

"Configuring NAT for IP Address Conservation" module

NAT maintenance

"Monitoring and Maintaining NAT" module

NAT commands: complete command syntax, command mode, command history, usage guidelines, and examples

Cisco IOS IP Addressing Services Command Reference

Standards

Standard

Title

No new or modified standards are supported by this feature, and support for existing standards has not been modified by this feature.

_

MIBs

MIB

MIBs Link

No new or modified MIBs are supported by this feature, and support for existing MIBs has not been modified by this feature.

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

RFCs

RFC

Title

No new or modified RFCs are supported by this feature, and support for existing RFCs has not been modified by this feature.

_

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html

Feature Information for Endpoint Agnostic Port Allocation

The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/go/cfn. An account on Cisco.com is not required.

Table 1 Feature Information for NAT Endpoint Agnostic Port Allocation

Feature Name

Releases

Feature Information

FPG: Endpoint Agnostic Port Allocation

12.4(24)T

This feature was introduced.

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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