Sometime ago I had a play with Jumbo frames and it wouldn't work so I gave up for a while but decided to come back too it this weekend. I've got a small gigabit network and I move large files around it and also backup across it. I noticed the speed was slow hence looking into Jumbo frames. Neither Vista or XP would work i disabled the firewall version 3 of Smart security but it still wouldn't work. In the meantime I also introduced two linux boxes and noticed that the transfer between them was a good 40 mb/sec faster than the XP or Vista/XP dual boot machine. So after messing around with some network tweaks still no go. I returned too Jumbo frames. Despite a direct connection between two machines Jumbo frames wouldn't work and the packets always were fragmented. Annoyed I reset the tcp/ip stack which promptly broke Eset firewall so I removed it and bingo I could use Jumbo frames. I re-installed version 4 and jumbo frames stopped working. I disabled the firewall and still wouldn't work. I then went into system settings and disabled system integration and jumbo frames worked. Clearly Eset have been taking lessons from other software vendors and disable doesn't mean disable as it should. On the other XP machine was Version three that wouldn't work at all and I couldn't see an option too remove from the system. So I removed version three installed ver four and jumbo frames still wouldn't work. Removed ver four again and fixed the winsock rebooted and reinstalled ver 4 and then disabled the firewall altogether. Bingo Jumbo frames worked. Next stage was to check network transfer and this was now back too 60 to 80 mb/s on the faster machine and 40 -50 mb's on the second slightly slower pc. I'm now on the windows firewall wondering when Eset are going to fix there firewall to allow jumbo frames Or is there a firewall rule that's blocking this which i don't know about If you have a network and you're using jumbo frames it may not actually be working. the firewall doesn't say it isn't and doesn't log an errors. Too check you need to ping "address of another machine" -f -l 2000 If you get a message saying the packets needs to be fragmentated but the flag is set this means Eset is preventing the transmission. Forgot to mention these were the latest versions of eset smart respectively.