Airport issue, too many MAC-adresses registered

[Menel]

When it is connected to the Airport it says that the IP adress is 91.100.21.42.

When i unplug the Airport and connect by putting the cable directly from the wall and into the computer is says 91.100.21.48.

Then you do not have your Airport in DHCP NAT mode.

You need to continue working on that. Make it look like Weasel oy's image.

 

[Weaselboy]

When it is connected to the Airport it says that the IP adress is 91.100.21.42.

When i unplug the Airport and connect by putting the cable directly from the wall and into the computer is says 91.100.21.48.

No that's your external IP address the Internet sees. I need to know the internal, local address assigned by the router to the PC. Look in Control Panel in the network settings and you should see an IP in the range I mentioned.

 

[RasmusTM]

I do not know how but it seems to be working now DHCP and NAT.
Thanks for all your help!