Friday, 15 January 2016

Stuff happens

I was woken too early, after a late night playing Civilization, with a report of a funny noise coming from the infrastructure. I dressed and had a gander.

The firewall I use is a Cisco Pix 506E, which is a totally obsolete piece of kit, but it gives up to 100 mbps of throughput, and since I have a 2 mbps line, it isn't going to feel the strain.

The noise was coming from that, and it was a gentle rurrr-rurrr-rurrr, which I diagnosed as a cooling fan getting close to the end of its life.

The Pix 506E has an Intel Celeron running at 300 mhz, which shows you how old it is. And that needs a heat sink, and the heat sink needs a fan. Actually, I'm not at all sure that such a low speed chip needs a fan, but it can't hurt.

Problem is, if I take the Pix out of service to look inside, all my comms are down. Solution is, another Pix 506E. So I configured my spare Pix to do the duty of the failing one, put it in place, took out the faulty one, opened it up and sure enough, the fan wasn't spinning as merrily as it should. This calls for a 50 cm fan, 1 cm thick. I rummaged through my box of fans, and found a 60 cm fan, 1 cm thick. A bit of surgery on the plastic plug, soon had it in place, and it spun nicely. I reassembled the Pix, and put it back, and everything worked fine.

Then I had a look at the spare, or at least I tried to. I couldn't plug the power into the box! The Pix 506E comes with a little power brick and a peculiar 8-way connector, and I just could not get the connector into the socket. I opened up the Pix, had a look, and saw that the socket had come adrift, and was half an centimeter inside the box. When I pushed it out, I was able to connect, and then I made sure that the configuration was exactly as it should be. I labelled it as "Spare Pix for data shed" and put it in a box.

In that box, I have another Pix 506E. That's intended to be a spare for the pix at Cheltenham, and it's configured and labelled as such. So if my Cheltenham Pix fails (Pixes dont fail, in my experience, but see below) all I have to do it a two hour drive, swap a box, and I'm good.

So Pixes don't fail, huh? Well, the fan does. Fans are a weak link on many computers. They are a cheap mechanical device, and they have a mean time between failure of maybe 20 years. But if you have 100 of them spinning happily, you won't need to wait 20 years until the first one fails.

The other part that fails, is the power supply, and I can tell that this is common by the number of Pixes on Ebay sold without power supply. I'm guessing that what's happening here, is a much loved Pix 506E power supply fails, and the sad owner decides to replace it with an ASA, Cisco's current firewall. The ASA is much more powerful than the Pix, and if you compare prices when new, much better value for money. Except that you can buy a Pix 506E on Ebay for typically £20, and you can roll your own power supply out of any used PC power supply. Here's how, part 1 and part 2.

In the middle of all this, I decided that one of those Pixes wasn't going to work (the one I couldn't plug the power in to), so I went on to Ebay and bid for a Pix, including power supply, for £20. I'll probably get it, but I'm not bothered if I don't, because I do actually have two spare Pixes.

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