NAT behaviour

Unanswered Question
Feb 23rd, 2009


on one of our border router we currently have NAT overload setup using one IP pool of 64 addresses. We have observed that the router use an IP address of the pool until all available ports are exausted. The it use the following one. Is possible change this behaviour?. Is possible that the NAT engine use all the IP address firstly, and after use the ports to each NAT entry?.


I have this problem too.
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Giuseppe Larosa Mon, 02/23/2009 - 06:00

Hello Antonio,

I've given a look at 12.4 ip addressing services command reference but I didn't find any option.

You can try the following:

divide your NAT pool in two pools

first pool is used first and without the overload option

(appears before in running config)

second pool is listed after and has the overload option.

But this reduces the number of possible concurrent TCP sessions to the internet

So I would keep the current configuration.

From ip nat translations you can track what an internal user is doing

Hope to help



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