Configuring communication with RADIUS 563Nortel WLAN—Security Switch 2300 Series Configuration GuideBefore you beginTo ensure that you can contact the RADIUS servers you plan to use for authentication, send the ping command to eachone to verify connectivity.ping ip-addressYou can then set up communication between the WSS and each RADIUS server group.Configuring RADIUS serversAn authentication server authenticates each client with access to a switch port before making available any servicesoffered by the switch or the wireless network. The authentication server can reside either in the local database on theWSS or on a remote RADIUS server.When a RADIUS server is used for authentication, you must configure RADIUS server parameters. For each RADIUSserver, you must, at a minimum, set the server name, the password (key), and the IP address. You can include any or allof the other optional parameters. You can set some parameters globally for the RADIUS servers.For RADIUS servers that do not explicitly set their own dead time and timeout timers and transmission attempts, WSSSoftware sets the following values by default:• Dead time—0 (zero) minutes (The WSS does not designate unresponsive RADIUS servers as unavailable.)• Transmission attempts—3• Timeout (WSS wait for a server response)—5 secondsWhen WSS Software sends an authentication or authorization request to a RADIUS server, WSS Software waits for theamount of the RADIUS timeout for the server to respond. If the server does not respond, WSS Software retransmits therequest. WSS Software sends the request up to the number of retransmits configured. (The retransmit setting specifiesthe total number of attempts, including the first attempt.) For example, using the default values, WSS Software sends arequest to a server up to three times, waiting 5 seconds between requests.If a server does not respond before the last request attempt times out, WSS Software holds down further requests to theserver, for the duration of the dead time. For example, if you set the dead time to 5 minutes, WSS Software stops sendingrequests to the unresponsive server for 5 minutes before reattempting to use the server.During the holddown, it is as if the dead RADIUS server does not exist. WSS Software skips over any dead RADIUSservers to the next live server, or on to the next method if no more live servers are available, depending on your configu-ration. For example, if a RADIUS server group is the primary authentication method and local is the secondary method,WSS Software fails over to the local method if all RADIUS servers in the server group are unresponsive and haveentered the dead time.For failover authentication or authorization to work promptly, Nortel recommends that you change the dead time to avalue other than 0. With the default setting, the dead time is never invoked and WSS Software does not hold downrequests to unresponsive RADIUS servers. Instead, WSS Software attempts to send each new authentication or authori-zation request to a server even if the server is thought to be unresponsive. This behavior can cause authentication orauthorization failures on clients because WSS Software does not fail over to the local method soon enough and theclients eventually time out.
