NAT question

Magic Johnson

On a lab I've just done I have 1 public IP 200.x.x.x. This needs to be statically mapped to a server in the DMZ. Boom. Done, easy peasy.

Next task:

Configure dynamic NAT so the PCs on the local LAN can access the internet. I was confused by this because it didn't specify a pool name or a range of IPs. I checked the answer and it said to use the interface, not an IP. Does this mean it uses the serial interface IP of the router? Which would be 52.X.X.X? The answer also revealed PAT configuration, in my opinion it is a badly worded question but nevertheless I would just like clarity on the matter!

Thanks!

EDIT: never mind checked the translations and it has used the interface ip. Didn't know you could do that! Is that a best practice or something to shy away from?

networker050184

It just depends on the setup. Nothing wrong with using the interface IP for NAT. Sometimes you will get a /30 on the WAN interface and then given a /28 or something to NAT to in which case you'd not use the interface IP.

Magic Johnson

So as long as you get an IP from the ISP to give your interface so you have that connectivity, you can use that for NAT/PAT and you don't need any additional IPs (for basic connectivity)?

networker050184

Yep, you can use the interface IP.

Magic Johnson

Interesting! Thanks again networker!

theodoxa

If they are using an interface, it is probably PAT and not regular Dynamic NAT. Dynamic NAT with a single public IP (interface) would be rather pointless as only 1 host would be able to get online at a time.