Q

Access point problems running on PoE

Powering a wireless access point using Power over Ethernet is usually a straightforward process, but troubleshooting an issue can be tricky. Wireless expert Lisa Phifer steps through some possible solutions and where to look for additional help in dealing with an access point powered on the end of a long cable.

I have an outdoor AP (Engenius EOC2610) which I have used for almost a year. Recently I ran into a problem when using a long (15 meter) Ethernet cable to link a fixed Internet connection to the AP. The link looks like this: Internet RJ-45 port to 1 meter Ethernet cable to PoE injector to 15 meter Ethernet cable to AP RJ-45 port. Although the AP's power LED is lit, other LEDs show some problems with LAN and WLAN connections. If I replace the 15m cable with a 1m cable, the AP works just fine. I have used a tester to verify that all cables are good. What could be wrong, and what should I try to overcome this problem?

An IEEE 802.3af-compliant mid-span Power over Ethernet (PoE) injector powers an AP by delivering up to 15.4 watts in-line, received through the AP's RJ-45 port.

You don't say what kind of Ethernet cable you're using, so we'll start there. For best results, use Category 5e or Category 6 cable. Older Cat3 or Cat5 cables can test fine but cause errors and performance degradation over longer distances or at faster data rates. Cat3 is only rated for 10 Mbps, while Cat 5 is rated for 100 Mbps at distances up to 100 meters. By comparison, Cat 5e can carry 1000 Mbps over distances up to 350 meters.

Of course, the distance between your Internet drop and your AP's 10/100 port doesn't come close to Cat5 limits. So next you should verify that your mid-span PoE injector is actually delivering enough power to meet your AP's requirements, accounting for cable loss. In particular, your Engenius EOC2610 uses a proprietary PoE design. If you're not using the manufacturer-supplied 24V PoE injector, that could definitely be your problem. Standard 802.3af PoE devices draw a max of 12.95 watts to account for cable loss.

Finally, forum posts for your AP suggest that others have experienced network connectivity issues which improved after firmware update. You might as well give this a go if your AP is running old firmware. If none of this helps, contact Engenius tech support or check Engenius user forums. Often the best way to fix a mysterious problem -- particularly one that involves a proprietary component like this -- is to ask others who have installed and used the same AP.

This was first published in August 2010

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