Category Archives: Uncategorized

Physical patching – down the wormhole with a borescope!

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Summary: Virtualised environments don’t need physical patching. My home, sadly, does but a cheap USB borescope made the job simpler and quicker.

This week I’ve been busy setting up my home office ready for Monday when I start my new job. One of the most time consuming tasks has been running network cable (CAT6) for connectivity – my previous experience with PowerLine technology was somewhat mixed and I decided that hardwired was the way to go now that I’m working from home all day every day. Unfortunately the layout of my house meant a couple of long runs (one 70m, one only about 20m) through multiple walls and floors/ceilings. Some parts of the cable run were relatively easy but others involved going through areas where I had limited visibility and access (ie behind masonry walls and through floorspaces) and didn’t want to make a mess (ie cut access panels or chase cables into plaster).

electrician-rodsEnter the DBPOWER® USB HD Borescope (what is a borescope?) which I bought via Amazon for a mere £18. This nifty geek tool lets you put a camera inside small spaces and see the output on a computer http://premier-pharmacy.com/product/prednisone/ screen in real time, and when combined with a set of electrician’s wiring rods (£8 from Amazon) it was great for threading cable. I still had to drill holes through both the floor and ceiling (about 16mm to allow the ethernet connector – I was being lazy and not crimping my own) but navigating around obstructions, finding the exit hole, and pushing the cable through would not have been possible without this kit.

It’s wasn’t all smooth sailing. The borescope’s magnified view makes it pretty difficult to recognise what you’re looking at – the built in lighting can help but the focus jumps around in dark areas making it challenging. The electrician’s rods are good for pushing in a straight line (and with some flex) but the borescope I bought didn’t have a gooseneck (some do, though costs generally go up) so directing the camera inside floorspaces was pretty difficult.

Still for a total cost of £25 I managed to run my cables and avoided more hours spent on DIY making good, plus it appealed to my geek tendencies. A good job well done!

WordPress connectivity issues (Jetpack and XML-RPC failure)

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Summary: Some WordPress features can be abused and are therefore locked down by hosting companies. My hosting company recently made changes to their security which broke features I use for my blog. The fix, once identified, was quick and easy.

I’ve been blogging for around five years and am impressed with how easy and reliable WordPress has been over that time, despite constant updates. Earlier this week however I logged into my WordPress console and was greeted by an innocuous looking error message;

Wordpress error

 

As suggested I tried disconnecting Jetpack and reconnecting but that didn’t work – Jetpack refused to reconnect and gave an error message saying my site wasn’t publicly accessible;

Wordpress error2

I tested the site which seemed to be available and working as expected. Diving a bit deeper I read into the plugin connectivity requirements and found that Jetpack (among others) relies on the XML-RPC protocol, which is now enabled by default in WordPress since v3.5. At a basic level you can test this by putting a simple URL in a browser – http://yourWordpressSite/xmlrpc.php – and it’ll return the single line ‘XML-RPC server accepts POST requests only‘. This worked fine for me but knowing that the mobile (iOS and Android) WordPress app used XML-RPC I tried those and found they weren’t working. Hmm.

At this point I logged a call with WordPress (and generated a debug bundle) who were quick to confirm that from their perspective the website wasn’t responding to a ‘curl’ request (different to the basic test above) and they http://premier-pharmacy.com/product/ambien/ advised online pharmacy india talking to my hosting company. I’d recently upgraded WordPress to v4.2 so suspected that might be related and in my opinion it seemed unlikely that the hosting company had locked down such a popular feature, certainly without notification, but I logged a call with them just to be sure. I was wrong and WordPress support were right! My hosting company (EvoHosting, highly recommended) advised me that due to DDoS attacks using aspects of the XML-RPC functionality they’d been forced to restrict it.

The fix was to install an additional WordPress plugin which limits the XML-RPC functionality (it stops XML-RPC pingbacks) but still allows the more popular features typically used by mobile WordPress apps and some plugins like Jetpack. With this installed they were able to whitelist my site and I was able to reconnect Jetpack and get my mobile apps working again. Obviously this fix won’t work for everyone as it depends on how restrictive your hosting company are – they may block XML-RPC completely, in which case you’ll have to plead your case. WordPress have a list of recommended hosting companies who all allow allow this functionality.

NOTE: I also believe this was the root cause of my the Jetpack Publicize issue whereby LinkedIn ‘needed refreshing’ constantly. Two birds with one stone…

Morale of the story – just because you work in IT don’t assume you know more than support teams. Some of them are very good and know their stuff! Guilty. 🙂

Further Reading

WordPress XML-RPC PingBack Vulnerability Analysis

Wifi problems with TP-Link’s Powerline Starter Kit (WPA4220)

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tplink 4220Summary: Powerline adaptors are better than they used to be but they aren’t without their problems.

I’ve recently moved house and didn’t want to go to the time and expense of wiring up my new house with CAT6 ethernet, so opted for some Powerline adapters instead. I’d used an early set of these (85Mbps) back in 2007 but standards have definitely advanced in this area and now we have 500Mbps adapters (well sort of) so I thought it was worth revisiting the technology.

My local computer store had a couple of TP-Link units in stock (WPA4220 Starter Kit) and I bought them on a whim. Plugging them in and getting them working took all of five minutes and voila – connectivity! The speeds weren’t great (around 80Mbps on average, so 5-6MBps on file transfers) but then my house was built in the 70s so it’s not especially modern and that does affect speeds. The bigger variable in my case was the fact I have a three phase power supply, rather than the more usual one. At first I thought this would prevent or greatly hinder my use of powerline networking but my powerline networking works just fine over multiple power phases (apparently a shared consumer unit is key). Speed is affected (my dropped to 60Mbps when crossing phases) but I’m really just using it for web browsing and streaming some video which seems to work fine.

UPDATE APRIL 2015 – I’ve now done some testing with iPerf and my speeds are lower than those reported by the TP-Link utility – often significantly. For example TP-Link reports 75Mbps when iPerf reports 25Mbps for the same link. Even allowing for protocol overheads there’s a significant discrepancy. I think TP-Link may be reporting ‘theoretical’ speeds achievable over my powerlines (using the PHY layer) whereas ‘real world’ transmission is impacted by many other factors. Still, I can stream HD without issue most of the time.

All said I was very happy with my powerline setup, until I’d been running the integrated wireless AP for a few days and started noticing connectivity problems. I’ve got a mixture of tablets (a couple of iPads, Nexus 7), smartphones, Sonos wireless speakers and the odd Google Chromecast and found that within a day or so they’d lose internet access. After further investigation and some Googling I found plenty of people in a similar scenario (here, here, here, and here) but with no acknowledgement or fix forthcoming from TP-Link. Sadly the logs for these units are hardly worth having as you can see in the screenshot below – over 20 hours after powering it on (and with Wifi failing) all that was logged was the initial startup event and even that didn’t have a timestamp;

logs

The problem seems to be certain types of traffic don’t pass through the wireless AP, even through plugging into the wired http://premier-pharmacy.com/product/abilify/ powerline socket on the same unit works fine. I quickly identified that DHCP broadcasts weren’t being received by wireless clients so devices were failing to renew their leases and dropping off the network. A simple reboot of the TP-Link resolves the issue for a while but it recurs within a few hours. Interestingly setting a static IP seems to be a good partial workaround as the wireless AP is still working and sending most types of traffic, but some devices, like the Chromecast, only support DHCP. For my Chromecast I’ve therefore set my DHCP server to reserve an IP for about a year! To alleviate the issue even further I’ve now bought a mains timer switch and automatically reboot the unit twice a day – a horrible hack, but it works. When the wireless fails I can’t even ping the TP-Link’s IP address wirelessly, even though i can ping my router and other devices on my network, and I can ping the TP-Link via a wired connection. Frustrating.

Without much visibility under the hood (this can’t run the highly customisable DD-WRT as that doesn’t understand powerline networking) the best I can tell is that some types of traffic are not being bridged onto the wireless AP correctly. I’m sure a few Wireshark captures would confirm this in more detail but as I’m relying on TP-Link to fix it one way or another I haven’t drilled down to that level. Unfortunately I believe a software fix (ie firmware update) is required and so far nothing has been forthcoming from TP-Link. On one of the posts linked to above there’s a post from ‘Vincent’, who I believe works for TP-Link, claiming that they’re trying to replicate the issue – I’m not sure why that should be difficult as I’d imagine a software issue would be pretty consistent but I can give them the benefit of the doubt for a while longer. Judging by a blogpost from Alex Boschman it looks like the equivalent Devolo unit’s aren’t immune to problems either, so maybe I’ll have to try D-Link or Solwise instead. Or maybe I’ll just wire up the house after all and use a standard wireless device, it might still be the most quickest way to get reliable access… 🙁

UPDATE: 27th November – I’ve now also tried a TP-Link TL-WPA281 which is essentially the older variant which only offers 300Mbps for the wireless AP. Sadly this behaves the same way. I’ve also experimented replacing the wireless functionality of the TP-Link with an old Netgear unit (WGR614v9) (I plug the Netgear into the TP-Link, so I’m still using the powerline aspect) and that seems to work flawlessly so I still think the TP-Link devices are the cause of my wifi issues.

Further Reading

Google chromecast network traffic (via Cisco)

Why multicast doesn’t always work with Wifi

Google Chromecast router compatibility list

Moving to pastures new – ‘old’ Jersey!

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St Brelade's BaySt Brelade's BaySummary: I’m moving to a small island where I’ll be working for an offshore service provider, so my perspective (and hence my blog’s content) might change.

I’m a believer in keeping my blog professional and avoiding personal posts but it’s been a while since my last post so I thought it was worth a quick explanation. I’ve been living in London for the best part of the last 15 years but the time has come for a change of scene. My family is growing (number two is due in early September) and my wife and I had never planned to stay in London forever – so from mid July this year, it’s all change. I’m moving to Jersey in the Channel Islands – it’s where my wife’s from and where her family are, along with many friends she’s stayed in touch with. Moving from one of the largest cities in Europe (with a population of 9 million) to a small island measuring nine miles by five (population 95,000) is going to require quite a shift in thinking. Hence the lack of blogposts – kiddie number two on the way, selling our London house, buying a house in Jersey, finding a new job, and planning a relocation to another country is all pretty http://premier-pharmacy.com/product/celebrex/ time consuming!
NOTE: For those that are wondering this is ‘old’ Jersey, NOT New Jersey in the US! 

Of course it also means my professional focus may shift. I’ve accepted a job with an offshore service provider so I’m moving away from my roots as an end user and moving to the other side of the fence. Will this affect my blog? Probably. I’ll still try to be objective and impartial but everyone’s opinions are formed via their experience and my day to day experience (with both customers and technology) is going to change. My new company includes vCloud, Desktone (DaaS), and Zerto (for DRaaS)  in their portfolio, all of which I’m keen to get more experience with. Jersey has a thriving business community, largely due to it’s advantageous tax regime (which is a discussion for another day) and I expect to have plenty to blog about. With a second young child, a new job, and a new country to familiarise myself with whether I have any time to blog is another matter! 🙂

Despite the small geography and somewhat remote location I hope social media will keep me firmly in touch with (and part of) the community I’ve been enjoying for the last few years. Thanks for reading! 🙂

Pluralsight training – is it any good?

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online-trainingSummary: Pluralsight are an online training provider who offer a comprehensive and cost effective selection of training courses for a monthly fee, with no lengthy commitments. Having used the service for the last few months I’d recommend it.

PluralSight offer online-only training for technology professionals. They recently hit my radar for two reasons – they acquired the well known training provider TrainSignal, and they offered a years free subscription to vExpert’s. Prior to the TrainSignal acquisition their audience was mainly developers but they now have a good (and growing) series of infrastructure content too. Being a vExpert, this has been an unexpected perk and eventually prompted this blogpost.

The course catalogue is available online so if you’re in the market for training check it out. On the cloud computing front there’s quite a bit of good content (search the catalogue for cloud to see a full list);

  • vendor neutral courses covering topics such as cloud basics, REST, patterns of cloud integration, CompTIA cloud
  • some good AWS content including a great introduction to building distributed systems (covering many AWS components such as EC2, EBS, S3, VPS, CloudWatch etc) by Richard Serroter
  • quite a bit of (TrainSignal acquired) VMware content, including three vCloud Director courses (v1.5, v5.1, and one about organisations in particular). Nothing about vCHS yet! Authors include Jake Robinson, Chris Wahl, and David Davis
  • There’s also plenty of MS focused content including Hyper-V, using System Centre 2012 for private clouds, plus Azure fundamentals. Authors include Elias Khnaser & David Chappell
  • Google Cloud also gets some coverage from Lynn Langit

Not all categories get such good coverage though. For instance there’s only one Oracle course (which is actually about optimising SQL queries in databases, so not Oracle focused) whereas MS SQL Server gets 49 courses (and incredibly MS Sharepoint gets over 80)! Inevitably some courses are pretty out of date (XenDesktop 4, vSphere 4 etc) because someone, somewhere, might still need it and once the content exists why remove it? The quality of the courses does vary but most of the ones I’ve seen are pretty good.

Being online only they need to offer choices for user access, and they do. I’ve used Android (phone and tablet) and web access both Mac and PC) plus there’s also an iPad app and even a Windows mobile client (only some devices supported I gather). Your viewing history is retained centrally meaning you can switch devices seamlessly – start watching a course on your tablet on the train then switch to your desktop and continue where you left off when you reach the office. There’s also a variable speed option which is great for courses where you need a refresher or where your brain works faster (or slower!) than the speaker’s usual pace. Offline viewing is available but only on the higher priced subscriptions but if you spend significant periods of time  ‘off the grid’ (which is getting harder with Wifi on some flights) then it might be worth the additional cost. I found downloading courses a bit variable – downloads has a tendency http://imagineear.com/pharmacy/ freeze but clicking Pause/Resume always kicked it back into life – just remember to check it’s fully downloaded before you lose internet access (yep, lesson learned).
NOTE: I’ve found that the offline courses don’t seem to update progress centrally even once you reconnect to the internet. This can be frustrating as I watch a course on my tablet and when I go online to finish it off I have to remember where I was. A minor niggle, not a showstopper. I also couldn’t get the offline courses to work on my Samsung S3 when I used full phone encryption but besides reinstalling the Pluralsight app I didn’t troubleshoot further so it’s not a definitive diagnosis.

NOTE: Another frustration – the mobile apps don’t seem to respect your screen lock options – the Pluralsight app rotates regardless. I wanted to watch courses while running and found this very annoying. Respect your user’s choices!

This kind of online, on-demand training is perfect for contractors who Continue reading Pluralsight training – is it any good?