ECIS4500 series Web Management Guide R02

server request from the switch. This scenario will loop forever. Therefore, the server

timeout should be smaller than the supplicant's EAPOL Start frame retransmission

rate.

Single 802.1X

In port-based 802.1X authentication, once a supplicant is successfully authenticated

on a port, the whole port is opened for network traffic. This allows other clients

connected to the port (for instance through a hub) to piggy-back on the successfully

authenticated client and get network access even though they really aren't

authenticated. To overcome this security breach, use the Single 802.1X variant.

Single 802.1X is really not an IEEE standard, but features many of the same

characteristics as does port-based 802.1X. In Single 802.1X, at most one supplicant

can get authenticated on the port at a time. Normal EAPOL frames are used in the

communication between the supplicant and the switch. If more than one supplicant is

connected to a port, the one that comes first when the port's link comes up will be the

first one considered. If that supplicant doesn't provide valid credentials within a certain

amount of time, another supplicant will get a chance. Once a supplicant is

successfully authenticated, only that supplicant will be allowed access. This is the

most secure of all the supported modes. In this mode, the Port Security module is

used to secure a supplicant's MAC address once successfully authenticated.

Multi 802.1X

Multi 802.1X is - like Single 802.1X - not an IEEE standard, but a variant that features

many of the same characteristics. In Multi 802.1X, one or more supplicants can get

authenticated on the same port at the same time. Each supplicant is authenticated

individually and secured in the MAC table using the Port Security module.

In Multi 802.1X it is not possible to use the multicast BPDU MAC address as

destination MAC address for EAPOL frames sent from the switch towards the

supplicant, since that would cause all supplicants attached to the port to reply to

requests sent from the switch. Instead, the switch uses the supplicant's MAC address,

which is obtained from the first EAPOL Start or EAPOL Response Identity frame sent

by the supplicant. An exception to this is when no supplicants are attached. In this

case, the switch sends EAPOL Request Identity frames using the BPDU multicast

MAC address as destination - to wake up any supplicants that might be on the port.

The maximum number of supplicants that can be attached to a port can be limited

using the Port Security Limit Control functionality.

MAC-based Auth