Sunday, October 21, 2012

BT Vision Network Problem

Comtrend Homeplug Weirdness!

If you are one of the poor souls who BT have conned that their BT Vision service is a viable alternative to BSKYB's satellite of Virgin Media's cable TV services then you may well have encountered the Comtrend PowerGrid 9020 home plug Ethernet access point kit. These kits are basically two plugin devices that enable an Ethernet signal to be carried over the mains voltage wiring of a house. This gives a more reliable and faster connection than WiFi which enables HD video to be streamed from the router to the BT Vision box. Thus enabling BT to charge you a small fortune for re-runs of crap TV shows you were fortunate enough to miss first time around. The upside of these is you can get pretty reliable wired Ethernet connection around your house without ripping up carpets and floorboards to run Cat5 cables. Having said that nothing beats proper wired Ethernet for reliability if you can it is well worth doing. Next time you rewire forward plan and run with Cat5e or even better Cat6 cable.

The reason for this post is the ham fisted way these things are set up. Well not set up as such but configured, because they should come pre-configured to just work out of the box, which for the most part they do. The problem come when they don’t work for some reason and the unsuspecting user starts pressing the little button on the front marked CONFIG/RESET. Now you'd have thought that maybe pressing this button would put it into a configuration mode and possibly pushing and holding it for a few seconds would perform a reset back to defaults. Well whatever you seem to do make the leds on the front of the device flash at random which only seems to be a way of telling you that all you now have is an extremely ugly expensive paper weight.

This problem is highlighted in a DigitalSpy forum post citing four interesting things regarding this problem:
  1. Basically the button has to be pressed really hard or it does nothing apart from making the leds flash.
  2. The red Status led does not necessarily mean there is something wrong with or that connection between units is slow.
  3. This can show up as being a phantom problem when it isn't really one if mains supply is interrupted.
  4. To reset the security buttons on both units must be pressed (real hard) simultaneously (you may need very long arms for this).
The instructions given by the manufacturer [pdf] can be found on the Comtrend's web site but as so often the case they aren't always straight forward. Doing the afore mentioned security reset turns an AP device into an EP device so that has to be turned back with more pressing of the errant CONFIG/RESET button and it all goes tits up again. Jonathan Hadden posts in his blog on a different approach to resetting the devices which gives much better feedback whether the reset has taken or not. I wish I'd seen his post before I had spent valuable time working it out for myself. To accomplish the factory reset the security has to returned to default settings as well as the networking set to DCHP etc.

I did it thus:

Noting the serial numbers of the devices the AP (Access Point) device has a serial ending in an A an the EP (End Point) device has one ending in a B, I wrote down serial of the AP device serial because I was going to need it later. Plugged the AP device into the mains and connect to the network with an Ethernet cable. Logged in to my router to see the ip address of the device, mine was under Attached Devices different routers vary where they display the info. Logged onto the 9020 AP device using the ip address in a web browser using the default password "admin", have these people never heard of security? The device's webserver threw up a configuration web page, I clicked "Change Configuration" then "Mac" where I changed the Network Identifier to the serial number which I'd made note of because I was going to need it later, clever huh? I gave the device an ASCII Encryption Key which I made note of because guess what... I was going to need it later, then I did several okays and came out of the configuration. Repeated the previous with the other device using the SAME SERIAL the one ending in an A and the Encryption Key I'd made a note of, smart or what? Again several okays and I had all green lights and the units are playing nicely again.

What I think's happening is the reset using the hardware button is not actually resetting the security which for some reason is getting screwed up. Resetting via the configuration webpage fixes this. Anyway Johathan Hadden also explains the operation so if mine confuses his most likely will clarify.

I know I'm moaning but these are pretty good little units which work really well most of the time it's just these little glitches that are a bit of an annoyance.  If you don't use BT Vision, I most certainly do not Comtrend 9020s are great for extending your wired network without the upheaval of rewiring and can be obtained at around £35 per set on eBay. Hang around because there are always loads for sale you may just get a bargain, I have seen them sell at auction or as little as £20 per set.

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