Dell POWEREDGE M1000E - Manual (Page 179)

Controlling Management Access 179
When multiple RADIUS servers are configured with different names, the
servers are in different groups. The primary/secondary designation and
priority applies to RADIUS servers only within the same group. Within a
named group, the switch always attempts to contact the primary RADIUS
server first. When two or more groups have been configured, the switch
determines which named group to contact first based on lexicographic order
(alphabetical) order.
For example, an administrator configures the following two RADIUS servers
in this order:
• Server Name is name1 and address is 1.1.1.1
• Server Name is name2 and address is 1.1.1.2
In this example, the switch has two configured authentication servers.
Because the name for each server is unique, the switch has two named
authentication server groups.
The switch always attempts to contact the name1 server before moving on to
name2. Even if the configured priority value of the name2 server is lower
(lower value indicates higher priority), the request would be sent to the
name1 servers. The request is sent to the name2 server only if the name1
server fails to respond.
To provide additional redundancy, the administrator can configure additional
servers within the named groups, for example:
• Server name is name1 and address is 1.1.1.3
• Server name is name1 and address is 1.1.1.4
• Server name is name 2 and address is 1.1.1.5
Now, the name1 server group includes three configured RADIUS servers, and
the name2 group has two servers. The administrator can configure the
primary/secondary status and priority within each group to control which
server is tried first. Between the two secondary servers, the one with lowest
priority value is tried if the primary server cannot be contacted. The RADIUS
servers in the name2 group are contacted only if no servers in the name1
group can be reached.
If an additional servers are configured in a group named abc, the primary
server in the abc group is contacted first because lexicographically, abc comes
before name1.