Authentication and Re-Authentication Problems

To authenticate to an AP (or to re-authenticate when a client roams from one AP to another) can also cause problems. Table 14-2 lists some common authentication performance problems and how to resolve the issues.

Table 14-2. Authentication Performance Issues

Problem	Probable Causes
Slow authentication affects users.	The RADIUS server might be heavily loaded. The WAN link might be slow, which causes slow authentication. The Dynamic Host Configuration Protocol (DHCP) server that issues IP addresses is slow to respond to address issuance.
Re-authentication delay when roaming between APs.	The AP might not be aware of the client's presence. The time it takes to re-authenticate depends on how often the client probes the AP. Misconfigured Wireless Domain Services (WDS), AAA server, or a slow WAN link.
WLAN throughput is slow.	Too many clients overburden the APs. APs might be poorly placed or experience weak radio signals because of obstructions, interference, or because they are out of range. Multicast applications, broadcast storms, interference, misconfigurations, and data rates can also cause slow throughput.