Reconfiguring mac for net connection

I have my mac connectedc to the net through a solwise plug (router), that gets the net through initial router connected to my sky router box for main pc.

net stopped working on my mac few days ago, but working fine on pc. stiched plugs/cables around and realised config problem with mac. When I connected mac to net first time with the solwise plug, it was just plugnplay, no confiq reguired. this time, i need to do som config, but do not know what?

anyone have any ideas?

the mac is meant to be quite solid, but still, could my mac have become infected, or is it simply a confir error?