Hardware on inherent site

Cisco SR2024C Repair

Mon, 28 Mar 2022 18:03:46 +0300

One of my friends at university gave me a broken switch that seemed broken and I decided to fix it. Join me on a pretty entertaining troubleshooting path that was not entirely necessary.

Backstory

This semester in university I am taking a CCNA class. The learning path is split across two semesters, next semester I’ll take CCNA 2 to be ready to get the certification. A few of my friends are also there an one of them happened to have a supposedly broken Cisco switch. Great opportunity to use it for hands-on learning, I thought. He said it wasn’t fully broken, it could turn on fine but would turn off after 10-20 minutes. Not that bad. A little fan was also missing from it but that would be no more than 5-10 euros to replace. He gave it to me one day, I took it home and that was that. After a bit of research I realized the switch wasn’t managed meaning it didn’t have Cisco iOS capabilities. Nevertheless, I like tech necromancy and network gear seldom goes unused. So that’s basically how I got a Cisco SR2024C.

Initial Findings

After checking that the power plug looked fine and the ports didn’t look damaged, I decided to turn it on. Indeed, after roughly 20 minutes it started boot-looping so the behavior was as described. The switch wouldn’t completely shut off, instead it followed a little pattern:

lights flash for a second the way they do when first plugged in
lights go out same as when normally booting
goto step 1

This meant that eventually anything plugged into it would drop off the network which is not good. At this point I’m suspecting the power supply since the device is pretty old, about 7 years past its End-Of-Life date.

Open Wide

Behavior confirmed and reproducible, we have a place to start from. The device would need to be opened anyway in order to replace the fan and I’d like to inspect the inside too. This specific switch is considered compact as noted by the ending C in its model number (SR2024C). Its width is a bit more than the width of the ports, 24 RJ45 gigabit ethernet ports and two miniGBIC. It has holes to attach rackmount ears if desired but I wasn’t provided those. On the front there is a plastic cover that fits over the 4 sets of ports (3 sets of 8xRJ45 and one set of the 2 miniGBIC) and also clips on to the top and bottom metal pieces. I dinged the plastic since I used a pair of scissors to pry it off but that’s alright, we’re going for functional not pretty. Following that, I had to carefully unhook some little metal tabs that held the top half of the metal case to the bottom half. Push a little here, pull a little there and ta-da! We’re in. The metal tabs were annoying to hook and unhook so I used a pair of pliers to twist them off. On the left side there is a mesh cutout big enough for a 40mm fan and on the right side it’s almost entirely mesh. Weird for a rackmountable device to have side-to-side airflow but what do I know. The bottom is entirely bare and so is the top with the exception of a Cisco logo.

Guts

There are two PCBs/boards inside, the main board and an open-frame power supply. They are connected by a weird cable I’ve never seen before and have connectors I’ve never seen before. On the PSU side it’s a 6-pin and a smaller 2-pin that merge into an 8-pin on the main board side. The power plug is attached to the PSU through a 2-pin cable with a similar connector as well as a chassis ground point. One good thing is that they all look removable and fairly easy to probe with a multimeter. Overall The internals appear understandable so I’m fairly confident I can at least identify the issue.

Power

Even though I commented about the ease of probing with a multimeter, I’m sad to say that I didn’t have one previous to this experience. Since I mostly work with software, either configuring or writing it, there was never a real need to own a multimeter. I hopped on to one of the local electronic hardware supply stores’ website and found one for around 15 euros, the UNI-T UT131C. It arrived the next morning so I got to work and confirmed what repair videos from similar switches said, the main board uses 5V power. The thing is, in those other videos the voltage was lower and that was what was causing issues. In my case it was nice and steady at 4,98V which is within margin of error meaning nowhere near enough to cause a malfunction. You can never be certain though so I had ordered some alligator clips which I used for powering the main board from an ATX PSU’s molex connector. It didn’t result in a normal boot but I at least got a power light. This ruled out my main hypothesis this far which was that the switch’s power supply was going bad.

Accidental Solution

In the process of hooking the switch up to the ATX power supply, I had it open for troubleshooting. Perhaps accidentally, just to confirm that the problem was still there I reconnected the built-in power supply again. After leaving for an hour or so to do something else, I came back and saw it wasn’t boot looping.

What?

Peculiar, I thought. Sure enough, plugging in my laptop to it showed a link light and the laptop got an IP address. What the… WAIT! By hovering over it I could feel the power supply putting out some heat. No way it could be this simple, right? Could it be overheating? I turned it off, closed the case and put a 120mm fan right up against the right side to pull air out of the switch. To my surprise that was adequate to keep it cool enough even while closed. This was so embarassingly simple that I had to test again. I turned the switch on, let it get to the point where it starts constantly resetting and then put the fan next to it. After about 5 minutes it started operating completely fine, I was in awe of how simply the problem was.

Fan Replacement

Moving on to a permanent solution, I needed a fan to replace then one that was missing. Looking things up online, I realized I need a 5V 1W fan that is 40mm wide and 20mm thick. However, th only thing I found was a 0.75W fan for 8,23 euros. Good enough I guess I’ll just get two of those, one for intake and one for exhaust. Funny thing about plans, the store had only one of the 0.75W version and then one that was 0.54W. Sigh… Fine, I’ll see how I’ll arrange them. A day later they came in, I tested them both out to see that they worked and put in the 0.75W fan just to be sure the internals get enough airflow. After a 24-hour testing period, I think it’s safe to say that the problem is solved.

Use Case

The current plan is to use the switch for a VLAN so I don’t have to waste multiple ports from my main 24-port switch and be reconfiguring them. Yes, port-based VLANs aren’t ideal but I need a place to test my next network remake without bothering everything else. Even with the new fan it’s not very quiet probably due to the whine that small fans make but I have plenty of noisy things in my room.

Conclusion

It was a long and weird journey but it ended well and I now have a new switch. The troubleshooting was fun, as it always is, the new tools are fun to have and I got a lesson about assuming the problem is more complicated than it is. Thank you for reading, I hope you enjoyed the journey cause I sure did.

GK61 Review

Sat, 04 Sep 2021 14:49:11 +0300

Intro

A little less than a month ago I bought a new keyboard, the HK Gaming GK61. It’s a 60% mechanical keyboard with RGB backlighting and a few different switch options. I’ve been using full-size membrane keyboards up until now so this was quite a bit different.

Overview

The GK61 comes in black, white, red or pink colors. It can be outfitted with gateron optical black, blue, brown, red, silver or yellow switches. As denoted by the name, its 60% size is a noteworthy selling point. Of course you can’t buy anything without RGB nowadays so it has that too. There is also a piece of software for configuring keyboard settings and saves them on the keyboard itself. I paid 70 euros for it in greece and I bought the black model with blue switches. With the big picture view out of the way, let’s get a bit more into the specifics.

Switches

As previously mentioned, I went with the gateron optical blue switches. This was mostly done because I like the noise and tactile feedback. I have a habit of bottoming out the keys so blues being a little slower for people that only barely activate the switch is not an issue. One potential drawback I was made aware of is that optical switches are not as common so replacing them is potentially more difficult. All the keys work fine, the sound is enjoyable, the physical feedback is good so no real complaints here.

60% layout

The size of the keyboard was a big change for me but also one of the big reasons I chose it. The unfortunate part is that it was only available in ANSI and not ISO locally but I’m aware that an ISO version exists. So what’s the deal with the 60% size? What does that mean exactly? There is no numpad, no F1 to F12, no end, home, pgup, pgdown, insert, delete or arrow keys. What does exist however, is an Function (Fn) key that acts as a modifier. This means that you can press Fn and something else to access the alternative function of a key. It saves size but can also be a bit annoying when you can’t access some keys directly. My personal changes were that I remapped caps lock to escape, right alt to left arrow, right ctrl to right arrow and escape to backtick. I’m slowly finding out that I’d prefer it if there were arrow keys that are just arrow keys on the main layer. Overall I like the small size but I think a 65% size with an ISO layout would be a better option for me.

Software

This is where things get a bit more gloomy. There exists software for the GK61 but not all software utilities are the same. In specific, I got a GK61v2 which has a serial number that starts with GK61US and things get interesting. The earlier versions of this keyboard use seemingly different firmware and different software utilities. Additionally, the alternative key functions are different for the GK61v2 so the M1, M2, M3 mode keys don’t work. At any rate, the software works fine. It allows remapping keys as well as customizing the lighting mode. Well…about that lightning customization… One would think that customizing one of the custom lighting modes would allow it to be permanently saved but no. If you make a custom one and then hit Fn and \ to cycle all of them, your custom mode will be nowhere to be found. This is unfortunate but I don’t mind since I just wanted to have a solid color and move on however it’s a downside worth mentioning. In totality the software side of the keyboard is a downside but it isn’t completely unusable I guess.

Conclusion

After almost a month of use, I’m overall pretty happy with the GK61. For 70 euros it was a fairly big investment, it was my first mechanical keyboard as well as my first 60% keyboard. Ideally I would like to have an ISO layout and separate arrow keys so when I upgrade in the future I’ll look at getting a 65% one with the appropriate key layout or possibly build a custom one. Overall I’d recommend it just be aware that it’s a lot smaller than what you might be used to. Thank you for reading, I hope you got something out of this.

Hardware Updates 2020

Fri, 15 Jan 2021 21:10:38 +0200

Getting a real storage server

During 2020 I got a few upgrades to my setup but I don’t remember the exact order of them. The most exciting was a 4U rackmount case that I could use to put up to 6×3.5″ hard drives by default and up to 9 with a 2×5.25″ to 3×3.5″ hotswap bay. Also I bought 3x4TB ironwolf hard drives to put in it initially because my 2x2TB mirror was regularly reaching 95% capacity meaning I had to prune the snapshots regularly and couldn’t use it to store more files on it. This made me warm and fuzzy inside but the old mirror had to sit on the bench for this transition. The power supply in my server had only 4 sata connections which would be enough for a boot SSD and one of the arrays but not everything at once. Initially that wasn’t a problem, installed truenas core on the ssd, set up the 3 4TB hard drives in a raidz1 configuration and started creating datasets and shares.

Adding some extra spice

After a while I wanted to access the data on the old miror which meant having to buy a new power supply so I got one. Namely the Corsair CV550 which has 7 sata power connectors, more than enough to power the five hard drives and the one SSD. Moving on to issue number two, data connections of which the motherboard only had 4 of. Admittedly 50 euros for an extra 4 sata ports seemed excessive but I saved up and acquired a nice and simple pcie card that did the job, no raid controller of course. Alright, we’re cooking with gas now, storage is taken care of.

Dealing with separation of concerns

However, I used to have a multi-purpose server and now it is just a NAS so I can’t run all my services anymore. Fear not because the trusty old and used Dell Optiplex came to the rescue. A shop near my house had one with an i5 2400 and 4gb of ram as well as a 250gb hard drive with windows on it for just 130 euros so I jumped on it. First things first, I can’t be using a mechanical hard drive for the operating system and proxmox doesn’t dual boot so the HDD has to be replaced. Luckily the 240gb SSD from when I originally built my desktop is still alive and it’ll do more than fine for this purpose. The hard drive will be put aside for now but rest assured I do plan to use it at some point.

Serially accessing memories about ram upgrades

More importantly, I got a handle on the ram situation of my NAS. Upgraded that beast from 12 to 16 gigabytes of ram which left the 4gb stick as a spare. Not being one to miss out on some extra ram, the spare got added to the optiplex. Going from 4 to 8 is nice but I want to run more than 2 virtual machines. With that in mind and a deal available, I added an 8gb to the optiplex. So we’re up to 16(8+8) gigabytes for the NAS and 16(2+2+4+8) gigabytes for the server.. An odd configuration but ram is ram and you bet I’ll use it.

Conclusion

Perfect, we had storage and now we have compute as well. How was this hardware used though? Check back later (or read the next post if it’s up) to find out.

Computers Were Faster

Tue, 29 Dec 2020 17:10:41 +0200

I own 3 operational 32-bit computers and I find them fun to play with and useful for software projects. Two of them are socket 475 and one of them is for slot form factor intel cpus. For the slot form factor one, I have a Celeron, a Pentium II and a Pentium III. The socket 478 based ones are much closer to usable for most of my use cases and the other one is fun to tinker with. How can that ““obsolete trash”” be useful, one might rightfully wonder.

My Use Cases

Development use case

Computers with less than 4GB of RAM and 2 cores are completely unusable and nobody should ever touch them, a “muh modern” advocate might cry. However I use those computers at least once a week for various tasks. First off, as a 32-bit docker registry. They don’t need to mix with the rest of the environment since there is no actual dependency between the 32bit and 64bit infrastructure. In addition, I can see how long it takes to build a certain image based on my software, test its performance and experiment with multi-architecture images. I would do the same thing for the raspberry pi but I only have one and that is not enough to warrant the effort. If the above wasn’t enough, they are very useful for testing things such as bare metal provisioning with a mostly DIY setup, how to configure new things I’m interested in such as the aforementioned DIY bare metal provisioning solution as well as new software stacks like ELK or TIG. They are also useful for API load testing and discovering where the bottlenecks are in a piece of software. On a newer multi-core cpu with loads of RAM and fast storage the bottleneck only shows up when the workload origanically overwhelms the software. However on a more limited system it becomes apparent very quickly where the bottleneck could be. For example, if the hard drive access is more than it should be, you hear the damn thing click every time so you know where to look.

Networking Use Case

In addition, old computers make great routers. Routers? They’re old and weak computers you might think. Well, that anemic MIPS or ARM based all-in-one network box that many ISPs provide you with has a CPU that is orders of magnitude slower than either of my 32bit boxes. For the router use case the same thing applies to the amount as well as speed of RAM. In fact, that’s how I originally got into DIY and selfhosting. The case that used to hold my server had one of the 32-bit motherboards and cpu and ram as well as a hard drive. After finding about pfsense and having that computer as a spare, naturally, I gave it a try. A quick install of pfsense later and I was learning about DNS, DHCP, ARP requests, MAC addresses, gateways, how to set up an access point and started my journey into learning about networking. Another use that requires a somewhat low-cost investment is getting a picoPSU or microPSU or something to that extent to power one of those 32-bit machines, connect it to a TV and use it as a dashboard display for monitoring software.

That’s not the end and imagination is the main limit into making this sort of hardware perform a useful task.

Conclusion

Before you go around calling older computers obsolete, check if PEBCAK is the bottleneck. Thank you for reading, if you have a cool project using older hardware, feel free to let me know.