Administrator Guide

Table Of Contents
326 Authentication, Authorization, and Accounting
Authenticated VLANs
Hosts that authenticate normally use a VLAN that includes access to network
resources. This VLAN may be assigned by the RADIUS server. Hosts that fail
authentication might be denied access to the network or placed into an
unauthenticated VLAN. Hosts that do not attempt authentication may be
placed into a guest VLAN. The network administrator can configure the type
of access provided to the authenticated, guest, and unauthenticated VLANs.
Much of the configuration to assign authenticated hosts to a particular VLAN
takes place on the 802.1X authenticator server (for example, a RADIUS
server). If an external RADIUS server is used to manage VLANs, configure the
server to use Tunnel attributes in Access-Accept messages in order to inform
the switch about the selected VLAN. These attributes are defined in RFC
2868 and their use for dynamic VLAN is specified in RFC 3580.
The VLAN attributes defined in RFC3580 and required for VLAN
assignment via RADIUS are as follows:
Tunnel-Type (64) = VLAN (13)
Tunnel-Medium-Type (65) = 802 (6)
Tunnel-Private-Group-ID (81) = VLANID
The tag value for the Tunnel-Private-Group-ID is parsed as the length of the
VLAN ID. The VLAN ID may consist of a VLAN name (not to exceed 32
characters) or a numeric value in ASCII (no alphabetic characters are
allowed) in the range 1–4093.
Dynamic VLAN Creation
If RADIUS-assigned VLANs are enabled though the Authorization Network
RADIUS configuration option, the RADIUS server is expected to include the
VLAN ID in the 802.1X tunnel attributes of its response message to the
switch. If dynamic VLAN creation is enabled on the switch and the RADIUS-
assigned VLAN does not exist, then the assigned VLAN is dynamically
created and the port PVID or native VLAN is set to the RADIUS-assigned
VLAN ID. Trunk mode ports are also made members of the created VLAN.
If the VLAN is already created on the switch, the port PVID or native VLAN
is set to the VLAN ID. This implies that the client can connect from any port
and be assigned to the appropriate VLAN based on the RADIUS server
configuration. This gives flexibility for clients to move around the network