NAT question

[karl.west]

Can some one give me an example of using "ip nat inside destination" ?

I know it enables NAT of the inside destination address. But I would like to see an example of how it is used. I check the cisco site but it doesn't go into detail or maybe

I just didn't find it.

Thanks

Karl

[thisisshanky]

You can use it for loadbalancing over servers. Suppose you have 4 webservers, which you want to load balance. Each will have a local (private address) which you define in a rotary pool. and the server will be known to outside world using a single public ip. This will be matched in a access list. and inside destination NAT can be used to load balance the servers to the outside world. Router will map the public ip to one of the local server ip on a round robin basis.

[hmeyer]

Hi,

can you write a configuration sample?

[mzwysm]

Hi Karl, this is Daniela and I've been working with network for about 1 year and 8 monthsand I think maybe I can help you with the NAT problems, because some months ago I have a similar problem.

First we need understand how does NAT works and as I don't know if you already have this information I try to explain it in few words.

Here where I've been working we use NAT to translate some invalid IP address to some valid IP address and it can be used between 2 networks that can't know it other.

For example:

Workstation A --- Switch A --- Router A --- Router B --- Switch B --- Server B

Workstation A needs to access Server B, but the Network A can't know the Network B by its real IP address, so we can use the NAT proccess to allow this comunication, as you can see above:

Router A -->

!

interface ethernet 0

ip nat outside

!

interface serial 0

ip nat inside

!

ip nat inside source static

We believe that the “ip nat inside source or destination” is related with the position of the “ip nat inside or outside” configuration, so we think that we can change it as example above:

Router A -->

!

interface ethernet 0

ip nat inside

!

interface serial 0

ip nat outside

!

ip nat inside destination static

We didn’t get any time to test it, but as soon as we can we try to use the example and inform you.

Regards ….

Daniela