Re: nat-reversible

[Alexei Monastyrnyi <alexeim@xxxxxxxxxxxxxxx>]

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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