Tricks of the Trade: Point-to-Point Links
As the Technical Support Manager here at AvaLAN Wireless, I talk to customers on a day in, day out basis. Over time I have learned several valuable tricks to help make troubleshooting easier. Today I'd like to share one of those with you.
When customers are installing any of our point-to-point wireless Ethernet bridges such as our AW900xTR-PAIR or our AW58300HTP-PAIR, one of the most common questions I get is this: Which radio should I put on the head end, and which radio should I put at the remote end?
Well, the short answer is that in 99%* of all cases, it doesn't matter one way or another. The radios functionally act as transceivers, both pushing and pulling data across the link with bi-directional data flow. The radios will perform that function regardless of whether the Access Point (or Bridge A) or the Subscriber Unit (or Bridge B) is at the head or remote end.
From a troubleshooting standpoint, the optimal answer is actually somewhat counter intuitive. I would recommend putting the Access Point at the remote end, and here is why.
Upon boot up, the Access Point and the Subscriber Unit act very differently in order to connect to each other. The Access Point is the smart one, and it sends out a beacon, broadcasting its network name, and waits for a Subscriber Unit to respond. The Subscriber Unit does not beacon anything, but simply listens on all frequencies until it hears a beacon that matches its own Network Name. If the Network Names don't match, they will never find each other.
More often than not, the remote end is...well, remote. It is physically more difficult to access if anything goes wrong. Fortunately, one useful tool for troubleshooting is the built in scanner. It has many applications, but here is one trick I have used. Imagine a scenario where you have a Subscriber at the head end, and an Access Point at the remote end. All of a sudden the radios are not longer connected and you need to find out more information. You log into the Subscriber and run the scanner, and you see the Access Point's beacon. So you know that the Access Point is functioning properly, so why isn't it connecting? Then you notice that someone changed the Subscriber Unit's Network Name on accident. You change it back, and the radios are up and running again! Or perhaps you don't see the beacon, and now you know that something other than simple configuration settings are wrong. Either way, it is useful information when troubleshooting and ruling out problems.
However, this kind of troubleshooting can only be done from the Subscriber Unit, so if the Subscriber Unit is the remote radio, you might have to go a few miles in the middle of nowhere with a bucket truck. This is why on point-to-point links I recommend placing the Access Point on the side that is harder to access. It simply opens up tools that wouldn't be available otherwise. No one wants things to go wrong. But when things do go wrong, you will have the tools to help make things right.
*The only exception to this is if you are using either the AW900xTR-PAIR or the AW2400xTR-PAIR and at the head end you have a large corporate network of more than 128 devices with MAC Addresses. In this situation, you will always want your Access Point to be at the head end.