As Johkal pointed out there is no external reset...What you can do to check that box again is:
Change your PC's network address to be 192.168.100.2 (You will temporarily lose internet connectivity)
Open up a browser and go to »
192.168.100.1 (You should get the diagnostics page
Check the DHCP box
Change your PC's network address to be DHCP
Viola, you should have the diagnostics page back if that's how you broke it.
Hope that helps.