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Re: nat-reversible posted 10/07/2006
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Heya.

"reversible - (Optional) Enables outside-to-inside initiated sessions to use routemaps for destination-based NAT"

http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cr/hiad_r/adr_i2h.htm#wp1178184

In other words, if you have a destination-based NAT, with usual NAT pool you will never get a traffic inside for this translation until there is a traffic flow from inside to outside (for given source-destination pair). This is because NAT entries for pools are created dynamically, so no traffic flow, no entry, basically.

If I understand things right, with "reversible" keyword the entry is created as soon as router detects an opposite traffic flow.

If you limit hosts number to 1 in both pool and catching ACL, you may think of it as of "destination-based" static NAT. :-)

HTH
A.

Chee Chew Leong wrote:
Anyone kind enough to guide me what is NAT with reversible keyword for.

If we take a look on from the configuration guide, what is the example trying to tell us and its functionality.

ip nat pool POOL-A 30.1.10.1 30.1.10.126 netmask 255.255.255.128
ip nat pool POOL-B 30.1.20.1 30.1.20.126 netmask 255.255.255.128
ip nat inside source route-map MAP-A pool POOL-A reversible
ip nat inside source route-map MAP-B pool POOL-B reversible
!
ip access-list extended ACL-A
 permit ip any 30.1.10.128 0.0.0.127
ip access-list extended ACL-B
 permit ip any 30.1.20.128 0.0.0.127
!
route-map MAP-A permit 10
 match ip address ACL-A
!
route-map MAP-B permit 10
 match ip address ACL-B

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