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authentication database, and then, if that fails using the configured RADIUS server.
Note: In the latter two modes that involve both RADIUS and the local database, if the local database includes
no username/password pairs, authentication will succeed only if the RADIUS server authenticates the user.
This differs from the Local Only mode where no authentication is performed when the local database is empty.
If the primary RADIUS server responds with an access rejection or an access challenge, the alternate RADIUS
server is not contacted. Only if the primary RADIUS server fails to respond at all is the alternate RADIUS server
contacted.
Therefore, do not attempt to select any of the RADIUS options unless you have a RADIUS server correctly
configured for this purpose. If you attempt to use RADIUS authentication without a RADIUS server, you will lose
your configuration access to the router.
The Advanced Security Options screen supports both a primary RADIUS server and an alternate RADIUS
server. When the router is configured to authenticate using RADIUS, it will first attempt to contact the
primary RADIUS server; if the primary RADIUS server responds, RADIUS authentication succeeds or fails
based on the response returned by the primary server. If and only if the primary server fails to respond, the
router will attempt to contact the alternate RADIUS server to authenticate the user. The router makes two
attempts per server, three seconds apart.
You can specify the RADIUS Server Addr/Name and the Alt RADIUS Server Addr/Name either by using a
hostname to be resolved using the Domain Name System (DNS) information configured in the router or by
using an IP address in dotted-quad notation. The RADIUS Server Addr/Name items are limited to 63
characters.
In addition to specifying the server's hostname or IP address, you must also specify a RADIUS Server
Secret and an Alt RADIUS Server Secret (if configured) known to both the router and the RADIUS server.
The secret is used to encrypt RADIUS transactions in transit. The RADIUS Server Secret items are limited
to 31 characters.
The router's RADIUS client implementation supports passwords longer than 16 characters and properly
encrypts such passwords per RFC 2138. Not all RADIUS server implementations handle passwords longer
than 16 characters.
RADIUS Identifier can be either an IP address or an arbitrary string to be used as the identifier in the
router's outgoing Access-Request packets. The RADIUS identifier is limited to 63 characters.
RADIUS Server Authentication Port specifies the UDP destination port to which the router's RADIUS
authentication requests will be sent. The default value is 1812, the official IANA-assigned UDP port
number for the RADIUS authentication service.
Certain security-related configuration changes cause the router to display a warning alert. Choosing either Local
then RADIUS or RADIUS then Local from the Security Databases pop-up menu when there are no configured
username/password pairs causes the router to present the following warning alert:
Security 16-7
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