Hi all, I have solved that problem I had with the LAN collisions; I just used the make-lan instead of newLan and everything began to work fine. I suppose I made a mistake in any of the newLan parameters. Here is how is working right now: ----- set lan [$ns make-lan $nodelist 10Mb 2ms LL Queue/DropTail Mac/802_3 Channel] ----- Thanks to everybody for the replies, /FCD