Chapter
3: Web Management
Security - Network - NAS (Network Access Server)
PoE Switch User Manual | 80
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.
Unlike port-based 802.1X, MAC-based authentication is not a standard, but merely a
best-practices method adopted by the industry. In MAC-based authentication, users are
called clients, and the switch acts as the supplicant on behalf of clients. The initial frame (any
kind of frame) sent by a client is snooped by the switch, which in turn uses the client's MAC
address as both username and password in the subsequent EAP exchange with the RADIUS
server. The 6-byte MAC address is converted to a string on the following form
"xx-xx-xx-xx-xx-xx", that is, a dash (-) is used as separator between the lower-cased
hexadecimal digits. The switch only supports the MD5-Challenge authentication method, so
the RADIUS server must be configured accordingly.
When authentication is complete, the RADIUS server sends a success or failure indication,
which in turn causes the switch to open up or block traffic for that particular client, using the
Port Security module. Only then will frames from the client be forwarded on the switch. There
are no EAPOL frames involved in this authentication, and therefore, MAC-based
Authentication has nothing to do with the 802.1X standard.
