The Wii uses DHCP over wireless from a Cisco 857W wireless router and then off over DSL with a NAT Pool (I have a small range of routed addresses) and PAT for overload based on the dialer0 address.
(In this post, IOS commands are shown in italic, and text in <> indicates that you need to substitute the value from YOUR setup)
Having worked out the internal IP address the Wii had from the DHCP server
show ip dhcp binding
and then what external IP address it had
show ip nat trans | inc <the_internal_ip_address>
I could look at the logs on the console using
This showed that UDP port 27900 was being blocked from the 207.38.11/24 network (judging from the few entries I saw).
Being a cautious guy I decided to just open up that port to the Wii from the outside world.
I have access list 102 bound inward to the dialer0 interface so the extra command needed was (this is one line of IOS):
access-list 102 permit udp 18.104.22.168 0.0.0.255 host <the_external_ip_address> eq 27900
Of course as I am using PAT for my DHCP hosts, at some point the address in the command above may change. I could statically assign an address from my routed pool but I would also have to bind the MAC address of the Wii to a static internal DHCP supplied address, and I can’t be bothered 🙂