Connecting NT Servers to Win2000 Server

Recently we installed a Win2000 Server and after configuring networking we noticed that the Stand Alone NT 4.0 Server and a NT4 Domain Server in LAN is not connecting thru Win2000 Server. Further it is the same case with an NT4.0 Domain Server whichwe are connecting thru WAN.
How can I connect these Servers ? Appreciate if necessary steps provided as I am new to Win2000 Server Administration.