What is the difference between an odd and an even front?

I3A it is nothing more than if the center is covered or not. Odd if there is a man over the center and even if there is no one over the center. Hope this helps.

13A,

an ODD FRONT has an ODD number of down linemen, and EVEN FRONT has an even number of down linemen. You can eagle up and down and cover the center or leave him uncovered and still have either front. A good example of an odd front is a 50 front (5 DLM's) and an evn front (4 DLM's) is some kind of 40 front. Mervin is right when he says in an odd front the nose is usually covered and vice versa in an even.

Coach Easton-TIGER ONE

This is not quite correct. The defensive fronts are as follows - Rob Ryan has a pretty good youtube clip on it. 3-4 and 4-3 (to my understanding) are more personnel packages than actual defensive fronts.

OVER (considered a "4-3 look")
Weakside 1 tech NT, strongside 3 tech DT, DE's both play Outside shade of End man on LOS (5 tech weakside and maybe a 6 or 9 tech over the TE), 3 Linebackers in the box.

UNDER (considered a "3-4 look")
Strongside 1 tech NT, weakside 3 tech DT ("becomes" 3-4 DE), Weakside DE really "becomes" a 3-4 OLB due to the shift, and your strongside linebacker shifts down to the line for a 5 man front, Mike and Will shift over.

ODD
Classic "3-4" look. Nose Tackle on the center in a 0 tech, both guards uncovered, DE's play a 4 or 4i technique over the tackles (2 gappers, or fake 2 gappers), linebackers line up mostly the same way as the Under front. The key here is that the guards are uncovered.

EVEN
4 down linemen and 2 linebackers (on the ends) on LOS, both guards and tackles are covered, but center is left uncovered.


BEAR (46)
Center and guards both covered (this is the only defense that does this), OLB play on the LOS in similar/the same techniques as in UNDER/ODD. Best cover linebacker (WILL) comes to the LOS to play a 7 technique inside shade of the TE, S/S replaces the WILL as weakside linebacker.