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Community Member

dynamic nat

Can anyone tell me why we would use dynamic natting, I unserstand statics etc but dont know why we would need dynamic ?

VIP Purple

Re: dynamic nat

Hello Carl,

the main reason for using dynamic NAT is that usually you have only a limited range of IP addresses available in a pool. Dynamic NAT entries time out and are only created when needed, that is, when there is traffic, while static NAT addresses do not time out, and remain in the translation table, regardless of wether there is traffic or not.

Here is what CCO says:

With dynamic NAT, translations do not exist in the NAT table until the router receives traffic that requires translation. Dynamic translations have a timeout period after which they are purged from the translation table.

With static NAT, translations exist in the NAT translation table as soon as you configure static NAT command(s), and they remain in the translation table until you delete the static NAT command(s).



Re: dynamic nat


AFAIK the basic purpose behind configuring dynamic nat is unavailability of enough public ips to be configured for the interal PC to get natted and go out to the internet world.

in Static we do one to map either using the nat statements so that our local lan servers or wkstations are visible from the outside world..

if u need to host some mailing or web or other servers which needs accessibiltiy from the outside world u need to deploy static nat.

Take an example that you have a block 64 ips in ur local lan and u have got 32 public ips and some servers too which needs to be access from the outside world.

In this case you can do one to one mapping to the servers and configure a pool which can be used by the other local lan pcs to go out to the outside world..

Again we have got one more scenario called PAT which is again port address translation where the translations basically happens on the port numbering details.

With PAT in place we have the liberty to have single public ip to cater the whole local lan behind that..


Community Member

Re: dynamic nat

im with it now, thanks a alot guys


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