You can try Wireless Network watcher to find the connected devices to your router :
http://www.nirsoft.net/utils/wireless_network_watcher.html
but the best thing to do, is to set the IP of the console to static. That way YOU decide the IP of the console instead of trying to find it every time.
on computer, open a command line window (start > run > cmd.exe)
type ipconfig and press enter
this is result on my computer:
Code:
Adresse IPv4. . . . . . . . . . . . . .: 192.168.1.2
Masque de sous-réseau. . . . . . . . . : 255.255.255.0
Passerelle par défaut. . . . . . . . . : 192.168.1.1
Like you see, my "IPv4" is of the form "192.168.1.x"
my computer is "2" and my router is "1"
private IP can usually be either:
192.168.0.x
192.168.1.x
10.0.0.x
go to WiiU, preference, network setting.
on "Get IP automatically" select "no"
then manually choose the IP for your console, for example "192.168.1.3" if "3" is not already used on your network.
mask : 255.255.255.0
gateway : 192.168.1.1 (the router's IP)
now you will have to set DNS manually too.
you can set the DNS to 192.168.1.1 if your router is filtering nintendo's servers to prevent the WiiU to be updated, or use OpenDNS IPs, or use other DNS (google DNS are 8.8.8.8 and 8.8.4.4, but be sure your router or a proxy are filtering nintendo's update server)