This sets which version of the EAPoL (EAP over LAN) protocol this port uses when acting as an 802.1x supplicant -- the range 1..2 corresponds to the original 802.1x-2001 EAPoL framing versus the revised 802.1x-2004 framing. An admin needs to match this to whatever version the upstream authenticator expects, since a version mismatch in the EAPoL frame format itself can prevent the authentication exchange from even starting, independent of credentials being correct. For example, if an upstream network's authenticator strictly enforces 802.1x-2004 framing and this is left at version 1, the switch's authentication attempts as a supplicant could fail at the protocol-framing level before credentials are even evaluated, worth checking before assuming a credential problem.