1-Port Power Injectors @ 1Gbps
Recently I ran into an issue when the need arose to provide temporary wireless connectivity for a single room in one of our buildings.
The task was easy enough: use one of our spare HP MSM422 access points along with a 1-port power injector since this building has older (non-PoE) switching equipment. Against my better judgement I told my boss I was going to run and install the AP after one of our meetings, because it “wouldn’t take more then a few minutes”. Past experiences have told me never to put a short time limit on any task (not matter how simple). I had already tested and provisioned the AP at my desk and I was confident in my ability to properly connect a few cables.
The problem was an interesting one as the AP was getting power from the power injector but it was not able to communicate with the controller to grab it’s config and other needed information. After 10 minutes of troubleshooting the AP at the remote building, I decided to bring the equipment back to the lab and see what was causing this issue. After working in the lab for a few minutes, the cause was clear and painfully simple.
The power injector I was using was one that we purchased from HP Procurve three or four years back. I could not locate the old part number, however when you order a 1-port power injector from HP they ship injectors made by PowerDsine. The particular model all of my testing was performed with was a 3001.
It turns out that this particular power injector has trouble with 1Gbps switchports. If you look at the switchport that the injector’s data port connects to, you will notice that link is never established. The way around this is to manually set the switchport that is being used with the injector to 100Mbps or 10Mbps.
Additionally, the current HP Procurve 1-port power injector (HP Part # J9407A) uses PowerDsine model number 3001G, which according to the documentation does support 1Gbps ports.