a console command

i remember 4 - 5 years back when i first got half life, one day i loaded in on 2 of my comps, i went into Lan game and made one, my sister went on her comp and joined my game, i then typed in something like map c0a1b or somethign like that, so it took us to the campaign, i then typed in a code (allow_multi_player_monsters) that is not the real code, but i am looking for that code to allow monsters in multiplayer, does anyone remember it?!

its mp_allowmonsters 1 to enable them

thank you very much!