472 Configuring Port and System Security
What is MAC-Based 802.1X Authentication?
MAC-based authentication allows multiple supplicants connected to the
same port to each authenticate individually. For example, a 5-port hub might
be connected to a single port on the switch. Each host connected to the hub
must authenticate separately in order to gain access to the network.
The hosts are distinguished by their MAC addresses.
When multiple hosts (for example, a PC, a printer, and a phone in the same
office) are connected to the switch on the same port, each of the connected
hosts authenticates separately with the RADIUS server.
If a port uses MAC-based 802.1X authentication, the option to use MAC
Authentication Bypass (MAB) is available. MAB is a supplemental
authentication mechanism that allows 802.1X unaware clients – such as
printers, fax machines, and some IP phones — to authenticate to the network
using the client MAC address as an identifier.
The known and allowable MAC address and corresponding access rights of
the client must be pre-populated in the authentication server.
When a port configured for MAB receives traffic from an unauthenticated
client, the switch (Authenticator):
• Sends a EAP Request packet to the unauthenticated client
• Waits a pre-determined period of time for a response
• Retries – resends the EAP Request packet up to three times
• Considers the client to be 802.1X unaware client (if it does not receive an
EAP response packet from that client)
The authenticator sends a request to the authentication server with the MAC
address of the client in a hexadecimal format as the username and the MD5
hash of the MAC address as the password. The authentication server checks
its database for the authorized MAC addresses and returns an Access-Accept
or an Access-Reject response, depending on whether the MAC address is
found in the database. MAB also allows 802.1X-unaware clients to be placed
in a RADIUS-assigned VLAN or to apply a specific Filter ID to the client
traffic.
NOTE: By default, all ports are in VLAN Access mode. A port that uses MAC-
based authentication should be configured to be in General mode.
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