when you play halo combat evolved on any level apart from the maw and 343 guilty spark try and kil as many covenant as you can by melee attack them. All you do is crouch then get a pistol or rifle out and hit the covenant with the but of your gun. if it dosen't work for you the just shoot them.
Http://www.gamefaqs.com/pc/291594-halo-combat-evolved/faqs/26388
That info has all console commands including how to setup a rotation of maps for your server, I gave that to someone else as well in a reply, hope that helps.