Can't Access Router Configuration To Get IP Address

we recently got a new router and added it to our network... works fine the problem now is that i'm trying to add some other ip addresses to access wireless internet (for security reasons the wirless internet is available only to one set of ip addresses) but now that i try to access the router config to get that ip address in i cant access the router config. i try multiple addresses but still nothing. i try to find the ip using cmd but it just gives me tunnel 000000000