Tag: Fix

Categories
Hardware

Replacement fans for GSM7224 switches

I have three old Netgear GSM 7224 Ethernet switches that I use from time to time in my lab network. These switches run at 1Gbps on each port which is still plenty fast enough for my needs.

I purchased them second hand on eBay some years ago. Soon after my acquisition, I replaced the 40mm fans in two of them and upgraded the firmware. All of my GSM7224 switches now needed new fans. One had stopped altogether, while the others had become very noisy.

Having done this repair before, this time around, I carefully selected replacement fans with the correct 2-pin plug already installed. I had to cut the plugs off the old fans last time and soldered them to the replacements. Lesson learned. With the new fans I could have glued M3 nuts into the receptacles but I prefer to use brass inserts like the OEM fans for ease of installation and avoid the glue.

Brass inserts for replacement fans

Six economically priced 5Vdc 40x40x10mm fans were purchased on eBay for £2.85 each, plus a bag of 50 M3 brass inserts for £2.19. The total cost of this repair was £19.29 in October 2024.

So why did I buy no name fans? A single Noctua fan costs £20, six of them would have set me back £120. I couldn’t justify spending an extra £100 on repairing these old switches. I would have to repair them five more times with cheap fans before breaking even on the cost of Noctua fans. If the switches were going to be used in a 24×7 production network, then better quality fans would make more sense. These switches are for a development lab and only powered on when needed.

Modification

I compared the fans on the switch that still had it’s original fans to those that I had repaired previously. All of the fans were installed the same way, sucking air out of the case. I have always been doubtful of the manufacturer’s choice to install them this way, so I decided to install the replacement fans blowing air onto the heatsinks instead. I am hoping that this will keep the case temperatures lower and make the fans last longer.

The heatsinks are in the air flow of the fans

The new fans have all been installed and are still quiet. Only time will tell if I should have bought Noctua fans. So far, I am happy with my cheap repair.

Replacement fans installed

A Future Project

The next project for these switches is to replace the awful configuration web app and equally awful text mode configuration. The older FSM726 switch had an easy to use terminal interface for setup. I still have a couple of them and it is far quicker to set one of these up over a serial terminal.

I am considering setting up a bastion host with SSH2 access over Ethernet and RS232C serial to the switch console port. I could create my own text mode interface that mimics the FSM726 which runs the appropriate sequence of commands on the switch to make the required changes. Alternatively, this could be a web app or an Ansible module. My Ansible controller could become the bastion host with the addition of a few more serial ports.

Categories
Hardware Linux Ubuntu

Unable to enumerate USB device on port…

I have an old PC with what appears to be a broken implementation of USB. I cannot obtain a BIOS update and there is no BIOS setting to switch off USB either. Very old Linux distributions would run on this PC, but only on those with USB support as loadable modules. For later kernels with direct USB support I would get continuous error messages to the console.

After spending some time Googling, I found this useful post

For Ubuntu 10.04 LTS I used the advice to create rules to deactivate USB entirely on this host. The first file that I created was /etc/udev/rules.d/20-disable-ehci.rules which contained the following code:-

ACTION=="add", SUBSYSTEM=="pci", DRIVER=="ehci_hcd", \
        RUN+="/bin/sh -c 'echo -n %k > %S%p/driver/unbind'"

When I rebooted the PC, it disabled one of the troublesome USB hubs but I was still getting error messages for another but much more frequently now. I experimented by creating a similar file to deactivate ohci but this didn’t do anything. I tried again with uhci and that worked, USB completely disabled.
/etc/udev/rules.d/30-disable-uhci.rules

ACTION=="add", SUBSYSTEM=="pci", DRIVER=="uhci_hcd", \
        RUN+="/bin/sh -c 'echo -n %k > %S%p/driver/unbind'"

So if you have two or more USB hubs throwing enumeration errors, try disabling both EHCI and UHCI, it worked for me.

Obviously, if you have any USB devices that you need to use with this host, forget it. You will need a new motherboard.

Categories
Ubuntu

Wireshark missing interfaces on Ubuntu 10.10

The old Dell laptop that I use for packet sniffing was in need of a rebuild after I had been experimenting with Zabbix. In hindsight, I shouldn’t have used the laptop that has become my network toolkit. I had well and truly messed it up and I was desperate to get it operational again.

Ubuntu 10.10 had recently been released and I had already downloaded the ISO images overnight. With a freshly burned CDR in my hand, I set about installing the new version. This laptop is primarily a network analysis tool so Wireshark was naturally the first application to be installed. It wasn’t long before I found that 10.10 has the same missing interface problem that I had experienced with 10.04. “No problem” I thought. “I will just use the fix that I found for 10.04“. Well, that didn’t work either. I left it for a day to have a think, and came back to it with a solution that I found on Launchpad. The fix is as follows.
In a terminal session, execute these commands:-

sudo addgroup –quiet –system wireshark
sudo chown root:wireshark /usr/bin/dumpcap
sudo setcap cap_net_raw,cap_net_admin=eip /usr/bin/dumpcap

Using your favourite text editor, add your user id to the wireshark group in /etc/group or use usermod instead:-

sudo usermod -a -G wireshark vince

Reconfigure the Wireshark Common package and answer ‘Yes’ to the question ‘Should non-superusers be able to capture packets?’ :-

sudo dpkg-reconfigure wireshark-common

Reboot, login and test Wireshark. The missing interfaces should be present now.