/shared2/sys/net/dhcp.dat

This file contains IP-addresses used by the Wii when connecting to the internet. Here's the C-struct:

struct
{
  u8 ip_1[4]; // Gateway? Currently unknown: 192.168.002.004
  u8 ip_2[4]; // Probably Wii IP inside network: 192.168.000.129
  u8 padding[24];
  u8 ip_3[4];  // Unknown: 199.183.190.001
  u8 padding_2[4];
  u8 ip_4[4]; // weird ip, started with 0x70 0x70.
  u8 padding_3[48]; // just some padding probably
} dhcp-file; 

I'm not sure yet what these different IPs are, but if you have this file, feel free to add better comments to the struct. :)

note: the will may prompt for an "sytem update" when it pings or "checks the internet contection" or stuff like that maybe the update (r) server ip is in this file???