I had a similar problem.

My Classic on System 7.1 is connected to an Asante Mini EN/SC connected to a NETGEAR 10BASE-T Ethernet Hub connected to a Linksys 54G Wireless Access Point which connects to a broadband router downstairs which has a default ip address of 192.168.1.1 but assigns ip addresses dynamically within a range.

After some experiment I found the following settings (re: images) worked for me but I found a lot of websites difficult to navigate around with MacWeb 2.0c and NSCA Mosaic 1.0.3.