Yes.
I was thinking, why doesn't it work. It had something to do with the IP addresses. So, I checked the IP addresses and Netmask from the PS3 itself (PS3 settings). Used these instead of the typical 192.168.0.1, .2, .3 and 255.255.255.0.
I'm using a linksys 250SD 5-port switch connected to a linksys router BEFSR41. Connect the PS3's to this switch with 3 ethernet cat5 straight cables. Check the IP address and Netmask from each PS3. (photo 13, 14, 15).
* Run GT4 on all three PS3's.
* Go to "options" and then go to "LAN play" (photo 1).
* "LAN settings" is the next menu that you get when you open LAN play (photo 2, 3, 4).
* Then go to "LAN connections" (photo 5). Photo 6 is the next menu.
* Don't forget to SAVE your settings! (photo 7).
* choose ARCADE MODE in the same menu as seen on photo 7.
* Choose "Multi LAN Race " (photo 8).
* Next menu: "internet service provider settings " (photo 9).
IP address: take the IP address and the Netmask from your PS3 settings (photo 13, 14, 15). Click OK and you get the next menu. You can connect your PS3's in this menu. I don't really know if it is necessary but I connect the side monitors first (PS3's) and then the middle monitor (PS3), which is the host. If you did it right, you'll be connected within 15 sec.
* This is the result. (photo 10, 11, 12).
I did some other tests.
1) Switch connected to the router and "Use DHCP" set to "YES" = (automatic IP and Netmask) also works, (see photo 9 (change "no" into "yes")) .
2) Switch disconnected from the router and "Use DHCP" set to "no" = IP address and Netmask from the PS3, also works. (see photo 9).
3) Switch disconnected from the router and "Use DHCP" set to "yes" = (automatic IP and Netmask) doesn't work, (see photo 9 change "no" into "yes").
If you have questions, PM me and I'll gladly answer your questions.