Okay this is a very easy glitch to do.
The following perks are recomended
.
Marathon pro
leight weight pro
I put the safest rout on the map for both spawns, they will take you to a fuel truck near the edge of the level.
go to the back of the truck and climb up the ladder.
Now run and jump to the part of the fence that sticks out you should land on the fence(not the orange thing)once you are on the fence simply crouch and your in:)
Light blue:safe rout from spawnsDark Blue:The truck you must get onPurple:Where you need to jumpI hope you can do this its really cool enjoy