Assuming that your system is windows.
Windows will assign ip to the ps3 with lan cable 192.168.137.1, based on this configure your ps3.
IP: 192.168.137.2
Subnet mask: 255.255.255.0
Default router: 192.168.137.1
Primary DNS: 192.168.137.1
if you confugura a fixed ip in your PC everything will be better, example.
IP: 192.168.1.101
Subnet: 255.255.255.0
Default router: it is usually 192.168.1.1, it is the same one with which they access the router to configure wifi password and others.
and DNS can use google 8.8.8.8 or 8.8.4.4.
If your pc connects via wifi you will need something additional, let me know.