How do I troubleshoot wireless access points (APs) losing connectivity?

Digg This!     StumbleUpon     Del.icio.us

RELATED CONTENT Wireless networking How radio frequency (RF) of microwaves alter wireless signal strength Stolen laptop recovery using remote access and wireless network SSIDs How is wireless access point (AP) coverage affected by frequency? Wireless AP SSID and channel configuration for a distribution network How 802.11n wireless APs in Greenfield mode affect nearby networks Monitoring your network to detect rogue access points (APs) Will 802.11x wireless products be compatible with 802.11n? How to find an SSID and identify neighboring WLANs How to create a Wi-Fi hotspot How to stop channel interference on 802.11x wireless access points Wireless LAN Implementation 802.11n wireless LAN access point market: Who's really in second place? Wireless LAN security: SonicWall joins crowded WLAN market Stolen laptop recovery using remote access and wireless network SSIDs Distributed antenna systems and WLAN: A network management burden Wireless AP SSID and channel configuration for a distribution network Solid 802.11n deployment prepares medical center for future demands How 802.11n wireless APs in Greenfield mode affect nearby networks How to create a Wi-Fi hotspot Beamforming, RF management key to 802.11n wireless LAN success Set up secure wireless networks with 802.11x, access points and bridges WLAN Security Wireless LAN security: SonicWall joins crowded WLAN market Stolen laptop recovery using remote access and wireless network SSIDs Enterprise wireless LAN security: 802.11 and seamless wireless roaming Monitoring your network to detect rogue access points (APs) Persistent, secure connections for roaming WiMAX, 3G and 802.11x 802.11n's impact on WLAN security Set up secure wireless networks with 802.11x, access points and bridges How wireless network encryption affects signal strength, connectivity New PCI compliance rules ban WEP, tighten wireless LAN security How to avoid the WPA wireless security standard attack

RELATED GLOSSARY TERMS Terms from Whatis.com − the technology online dictionary 802.11a  (SearchNetworking.com) Asynchronous Pulsed Radiated Incident Light  (SearchNetworking.com) cognitive radio  (SearchNetworking.com) direct sequence spread spectrum  (SearchNetworking.com) frequency-hopping spread spectrum  (SearchNetworking.com) phase-locked loop  (SearchNetworking.com) radio frequency  (SearchNetworking.com) wireless mesh network  (SearchNetworking.com)

RELATED RESOURCES 2020software.com, trial software downloads for accounting software, ERP software, CRM software and business software systems Search Bitpipe.com for the latest white papers and business webcasts Whatis.com, the online computer dictionary

I have seen access points malfunction in this manner for three reasons:

1. Some APs have an option to automatically disable themselves when they sense they have lost wired network connectivity. This feature is intended to stop clients from connecting to an AP with a strong wireless signal but no upstream connectivity in multi-AP WLANs. I suggest plugging the AP, its normal Ethernet uplink, and a LAN analyzer into a hub. Use the analyzer to monitor packets to see what happens just prior to the AP losing signal. If you don't see anything, try running a continuous ping (ping –t) against the AP until signal is lost. (I'm assuming your AP does not have a serial port through which you could simply check its log to see what's happening.)
2. Another less-likely possibility is that your AP is experiencing a periodic denial of service (DoS) attack that causes it to freeze. The DoS attack could be intentional -- for example, an attacker sending random connection requests to cause the AP's association table to overflow. Or it could be accidental, like a nearby source of RF interference that overwhelms your AP's own signal. 802.11 DoS attacks can be seen by monitoring the air with a WLAN analyzer like Wireshark. Non-802.11 interference can be diagnosed using a wireless spectrum analyzer like Wi-Spy.
3. Alternatively, many APs exhibit this kind of behavior when they experience a firmware bug or hardware failure like overheating. A quick fix for corrupted firmware is often to reinstall the latest and greatest firmware update. Unfortunately, hardware failures usually require AP replacement -- I have seen more than a few APs turned into doorstops for this reason.

To learn more wireless troubleshooting tips, view SearchNetworking.com's wireless troubleshooting learning guide.