Lagging while in lan

Dunno if its from your side or ours, but we dont lagg like that in other games, its delays and freezlagg, all ping related, but only when we play together, makeing the game unplayeble on hc, and almost unplayeble in normal too since we are 63-64 and do maps, we die quite allot too the lagg and cant finnish 50% of the maps we do, and the resault is we done about 40 maps or so and are stuck on 60 maps still (dont have any at all atm) but you get my drift. just thought id post it here so mabey i can get some answers/tips on how to get it fixed.