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Table Of Contents
Restrictions for the Scalability for Stateful NAT Feature
Information About Scalability for Stateful NAT
How to Configure SNAT in HSRP Mode
Configuration Examples for SNAT in HSRP Mode
Configuring SNAT in HSRP Mode: Example
Scalability for Stateful NAT
The Scalability for Stateful NAT feature allows Stateful Network Address Translation (SNAT) to control the Hot Standby Router Protocol (HSRP) state change until the NAT information is completely exchanged. The ability to change the default TCP mode to User Datagram Protocol (UDP) mode, and the ability to disable asymmetric queuing have been added. When UDP mode is used, SNAT will send messages over UDP mode using a proprietary acknowledgement/retransmit mechanism.
History for the Scalability for Stateful NAT Feature
12.4(3)
This feature was introduced.
12.4(4)T
This feature was integrated into Cisco IOS Release 12.4(4)T.
Finding Support Information for Platforms and Cisco IOS Software Images
Use Cisco Feature Navigator to find information about platform support and Cisco IOS software image support. Access Cisco Feature Navigator at http://www.cisco.com/go/fn. You must have an account on Cisco.com. If you do not have an account or have forgotten your username or password, click Cancel at the login dialog box and follow the instructions that appear.
Contents
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Restrictions for the Scalability for Stateful NAT Feature
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Restrictions for the Scalability for Stateful NAT Feature
The Scalability for Stateful NAT feature is not available in Primary/Backup mode.
Information About Scalability for Stateful NAT
Before enabling the Scalability for Stateful NAT feature, be sure you understand the following concepts:
SNAT Feature Design
Two or more Network Address Translators function as a translation group. One member of the group handles traffic requiring translation of IP address information. It also informs the backup translator of active flows as they occur. The backup translator can then use information from the active translator to prepare duplicate translation table entries, and in the event that the active translator is hindered by a critical failure, the traffic can rapidly be switched to the backup. The traffic flow continues since the same network address translations are used, and the state of those translations has been previously defined.
Only sessions that are statically defined already receive the benefit of redundancy without the need for this feature. In the absence of SNAT, sessions that use dynamic NAT mappings would be severed in the event of a critical failure and would have to be reestablished. Stateful NAT enables continuous service for dynamically mapped NAT sessions.
SNAT can be configured to operate with HSRP to provide redundancy and the active and standby state changes are managed by HSRP.
Benefits of SNAT Scalability
This feature enables SNAT control of the HSRP state change until the NAT information is completely exchanged.
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How to Configure SNAT in HSRP Mode
This section contains the following procedure:
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Configuring SNAT in HSRP Mode
Perform this task to configure an HSRP router with SNAT.
SUMMARY STEPS
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DETAILED STEPS
Configuration Examples for SNAT in HSRP Mode
This section provides the following configuration example:
Configuring SNAT in HSRP Mode: Example
Configuring SNAT in HSRP Mode: Example
The following example shows how to configure SNAT in HSRP mode with asymmetric queuing disabled and UDP enabled:
!standby delay minimum 30 reload 60standby 1 ip 10.1.1.1standby 1 name SNATHSRPstandby 1 preempt delay minimum 60 reload 60 sync 60!ip nat Stateful id 1redundancy SNATHSRPmapping-id 10as-queuing disableprotocol udpip nat pool SNATPOOL1 10.1.1.1 10.1.1.9 prefix-length 24ip nat inside source route-map rm-101 pool SNATPOOL1 mapping-id 10 overloadip classlessip route 10.1.1.0 255.255.255.0 Null0no ip http serverip pim bidir-enableAdditional References
The following sections provide references related to the Scalability for Stateful NAT feature.
Related Documents
Stateful NAT Phase 1 configuration tasks
Stateful Failover of Network Address Translation (SNAT) Phase I, Release 12.2(13)T
Stateful NAT Phase 2 configuration tasks
NAT Stateful Failover for Asymmetric Outside-to-Inside ALG Support—Stateful NAT Phase 2, Release 12.3(7)T
IP NAT commands: complete command syntax, command mode, command history, defaults, usage guidelines, and examples
Cisco IOS IP Addressing Services Command Reference, Release 12.4T
IP NAT configuration tasks
"NAT" section of the Cisco IOS IP Addressing Services Configuration Guide, Release 12.4
Standards
MIBs
None
To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:
RFCs
Technical Assistance
Command Reference
This section documents one modified command only.
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ip nat stateful id
To designate the members of a translation group, use the ip nat stateful id command in global configuration mode. To disable the members of a translation group or reset default values, use the no form of this command.
ip nat stateful id id-number {redundancy name mapping-id map-number [protocol {tcp | udp}] [as-queuing {disable | enable}] | {primary ip-address-primary backup ip-address-backup peer ip-address-peer mapping-id mapping-id-number}
no ip nat stateful id id-number
Syntax Description
Command Modes
Global configuration
Command History
12.2(13)T
This command was introduced.
12.4(3)
The protocol and as-queuing keywords were added.
12.4(4)T
This command was intregrated into Cisco IOS Release 12.4(4)T.
Usage Guidelines
This command has two forms: HSRP stateful NAT and manual stateful NAT. The form that uses the keyword redundancy establishes the HSRP redundancy method. When HSRP mode is set, the primary and backup NAT routers are elected according to the HSRP standby state. To enable stateful NAT manually, configure the primary router and backup router.
In HSRP mode, the default TCP can be changed to UDP by using the optional protocol udp keywords with the redundancy keyword.
To disable the queuing during asymmetric routing in HSRP mode, use the optional as-queuing disable keywords with the redundancy keyword.
Examples
The following example shows how to configure SNAT with HSRP:
!standby SNATSRSP ip 10.1.1.1 secondarystandby delay reload 60standby 1 preempt delay minimum 60 reload 60 sync 60!ip nat Stateful id 1redundancy SNATHSRPmapping-id 10as-queuing disableprotocol udpip nat pool SNATPOOL1 10.1.1.1 10.1.1.9 prefix-length 24ip nat inside source route-map rm-101 pool SNATPOOL1 mapping-id 10 overloadip classlessip route 10.1.1.0 255.255.255.0 Null0no ip http serverip pim bidir-enableThe following example shows how to manually configure SNAT:
ip nat stateful id 1primary 10.88.194.17peer 10.88.194.18mapping-id 10ip nat stateful id 2backup 10.88.194.18peer 10.88.194.17mapping-id 10Related Commands
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