Specifications

CHAPTER 9
Wireless LANs in a Campus Network
Client Connectivity
Clients associate with an access point as follows:
Access points send out beacons announcing information such as SSID, unless configured not to.
Step 1. The client sends a probe request and listens for beacons and probe responses.
Step 2. The AP sends a probe response.
Step 3. The client initiates an association to the AP. 802.1x authentication, and any other security information is sent
to the AP.
Step 4. The AP accepts the association. SSID and MAC address information is exchanged.
Step 5. The AP adds the client’s MAC address to its association table.
Clients can roam between APs, but the APs must be configured with the same SSIDs/VLANs and security settings. Layer
2 roaming is done between APs on the same subnet and managed by the switches using a multicast protocol: Inter-Access
Point Protocol (IAPP). Layer 3 roaming is done between APs on different subnets and is managed by the wireless LAN
controllers. The switch connected to the AP updates its MAC address table when a client roams.
Short roaming times are needed for VoIP to reduce delay. A client will attempt to roam (or associate with another AP)
when
n It misses too many beacons from the AP.
n The data rate is reduced.
n The maximum data retry count is exceeded.
n It is configured to search for another AP at regular intervals.
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CCNP SWITCH 642-813 Quick Reference by Denise Donohue