They are supposed to, but talk with any sysadmin or a guy hosting a big lan-party and you will know that, that isn't the case. I have hosted several 300-400 pe

They are supposed to, but talk with any sysadmin or a guy hosting a big lan-party and you will know that, that isn't the case. I have hosted several 300-400 person lan-parties and there is always two or three machines with the same MAC-address. A MAC-address is somewhat unique, but it happens that manufactures re-use the address twice or more. I have a feeling that cheaper brands do it more, but I have nothing to back that up. There is a discussion here that backs up my claim: http://superuser.com/questions/268006/are-mac-addresses-unique-when-coming-out-of-the-factory http://superuser.com/questions/268006/are-mac-addresses-uniq...