Last month, I took the Certified Wireless Technology Specialist (CWTS) exam. This is issued by CWNP, who are similar to CompTIA, i.e. it’s a vendor-neutral exam rather than being based around specific technology (e.g. Cisco access points).

The CWNP website says: “The CWTS certification validates the knowledge of enterprise WLAN sales and support professionals who must be familiar and confident with the terminology and basic functionality of enterprise 802.11 wireless networks.” Similarly, when I booked the exam on the Pearson Vue website, they list it as: “PW0-071: Certified Wireless Technology Specialist – Sales (CWTS)”. This exam isn’t a pre-requisite for any of the higher qualifications, so you could start with the CWNA instead (“the foundation level enterprise Wi-Fi certification for the CWNP Program”). As I understand it, the main difference between the CWTS and the CWNA is “what vs. how”, although I don’t really know enough about the CWNA yet to comment in detail.

Having said that, I learnt a lot by preparing for this exam, and I think there is quite a bit of technical detail in here. For instance, here’s section 3.6 of the exam objectives:

Understand and apply basic RF antenna concepts

  • Passive Gain
  • Beamwidth
  • Simple diversity
  • Polarization

I think there are a lot of IT professionals who would struggle to define all of those terms. Similarly, here’s one of the sample questions from the start of the textbook:

What can contribute to voltage standing wave ratio (VSWR) in an IEEE 802.11g wireless LAN circuit?

  1. Output power of the access point
  2. Impedance mismatch
  3. Gain of an antenna
  4. Attenuation value of cable

So, this is a bit more involved than just saying “Buy a wireless router and plug it in at home”!

Continue reading “CWTS”

Installing dd-wrt on a Linksys WRT320N wireless router

Back in 2011 I switched ISPs to A&A, primarily because they support native IPv6. Incidentally, 3 years on I see that you still can’t get IPv6 from Zen, so I made the right choice by switching.

Windows has had IPv6 support included by default since 2006 (i.e. Vista onwards), so the missing piece of the puzzle was my wireless router (a Linksys WRT320N). Unfortunately, the built-in firmware doesn’t support IPv6. (Source: Linksys devices that support IPv6.)

So, I investigated open source alternatives. There are a few different firmware projects out there, which all seem to be based on Linux. According to the OpenWRT wiki, it isn’t supported on the WRT320N. However, the WRT320 is listed in the dd-wrt router database, so I chose that instead. JP Hellemons wrote about this in 2010 (How I upgraded my Linksys WRT320N to DD-WRT v24); he also checked Tomato and HyperWRT, and neither of those were compatible. However, apparently the NoUSB edition of Tomato USB does does support the WRT320N.

Just to forewarn anyone else who’s in a similar position, this isn’t a simple process. Here’s a good (valid) rant about how complex it is. I heard a good phrase a while ago: “Open source software is only free if your time is worthless.” I.e. if you assume that your time is valuable, consider how long it will take you to get a system working. Is it worth paying money to save yourself some time? For instance, in this case I could replace my router with a different model that has IPv6 support built in. (You will still need to invest some time in learning any system, but maybe you could reduce that from a day to an hour.)

In brief, I (eventually) got the router working fine with dd-wrt over IPv4. IPv6 took a bit longer; I’ve elaborated on that in another post (Native IPv6 in dd-wrt).

Continue reading “Installing dd-wrt on a Linksys WRT320N wireless router”

CompTIA exams

Back in 2007, I passed the CompTIA A+ exams. Since then, there have been a few changes to the way these exams work. Unfortunately, CompTIA haven’t done a very good job of explaining it all; it makes volume licensing seem clear and simple by comparison!

In brief, if you currently have the A+, Network+, or Security+ qualification, you should enroll in the CE program. The deadline for enrollment is 31st December, so there’s not much time left. (If this applies to anyone you know, please pass this info on to them.)

Continue reading “CompTIA exams”


I’ve recently swapped ISP, from Zen to Andrew & Arnold. More specifically, I had an ADSL line from Zen, and I now have a VDSL line from A&A; this uses FTTC (Fibre To The Cabinet), which BT have just deployed in my local exchange. I’m happy with the new service, and it’s definitely faster than what I had before: according to Broadband Speed Checker my download speed is 24368 Kbps, whereas it was about 3500 Kbps before. Unfortunately, the transfer didn’t go smoothly, and I wound up with no internet connection for eight days; I had to rely on my Orange mobile broadband dongle, which is roughly equivalent to dial-up speed. I’m not quite sure what went wrong, but there was definitely a failure to communicate somewhere along the line. If you’re considering a similar move, this post should give you an idea of what to expect.

Continue reading “VDSL”

Protecting passwords

When I created accounts with Facebook and LinkedIn, both websites asked me for my email password to help me find people I know. The idea is that they can log into my email account, go through my address book, then search their own database for people with matching email addresses. That would certainly be convenient, and save me some time, but I think it’s a very bad idea.

Continue reading “Protecting passwords”

RAIDers of the lost sleep

Early in my career, I noticed an error when I rebooted a server, saying that one of the RAID drives had failed. The server was able to keep running, but the drive needed to be replaced, so one of my colleagues came over with a new one. The drive was hot-swappable, so he was quite cheerful about the fact that we wouldn’t need to shut the server down first. However, we disagreed about which drive had failed; the error message referred to drive 2, and there were 5 in total, but I thought that the numbering would start at 0 while he thought that it would start at 1. He outranked me, so he pulled out the second drive. Unfortunately, this turned out to be the wrong one (i.e. one of the working drives), so the entire server crashed, and we had to spend our Friday night re-installing Windows from scratch.

Continue reading “RAIDers of the lost sleep”

Fake virus warnings

Someone called me earlier, because she had a big virus warning on her screen. This was actually a hoax (a web page trying to install malware), and it’s useful to be aware of it so that you know what to recognise.

I identified the website which was responsible, but it’s now been taken down. So, the purpose of this post is to warn you about similar sites rather than this site in particular. I observed the same behaviour in IE8 and Firefox 3.6.12 (on Windows 7), but I haven’t tried any other OS/browser.

Continue reading “Fake virus warnings”