Jiri is passionate about mobility ranging from Wi-Fi to folding bikes;-) He is a Wi-Fi Technical Architect at Cisco UK and proud member of the Cisco Live Network Operations Team and WLAN Pi development team. If not working, he is most likely riding his Brompton bike.
Optionally, you can order an AP + antenna collocation “pocket”, which the Catalyst 9130AXE slides nicely in. It is aesthetically pleasing it, and all it takes to install the AP and antenna is a single mounting bracket. You don’t have to worry about mounting the access point and antenna separately. This drastically simplifies temporary deployments – just think about Cisco Live for example.
Please always refer to the official Cisco documentation for the latest information and package contents.
With the first consumer Wi-Fi 6E routers already shipping, and enterprise access points being worked on, I think it is now time to up my iperf3 game. While the standard 1 Gbps adapters push around 950 Mbps of TCP traffic, the iperf3 server will sooner or later become a bottleneck for throughput measurements.
Raspberry Pi 4 (RPi4) is widely available, and there is a chance that you might already own one. So, the question is, can it support multigigabit speeds?
Although it does not have any PCI Express slot available, it does have a couple of USB 3.0 ports. I researched USB 3.0 multigigabit NBASE-T Ethernet adapters, and purchased a few. At the time of writing, Linux kernel 5.10 is the Raspberry Pi OS gold standard, and that’s what I used for all tests.
TL;DR … give me the short answer
The maximum TCP throughput Raspberry Pi 4 iperf3 server can handle with a 5 Gbps USB 3.0 Ethernet adapter. These were 90-second iperf3 tests with standard 1500-byte MTU and a single iperf3 stream.
Download (from RPi4 server to a client): 2.05 Gbps
Upload (from a client to RPi4 server): 528 Mbps
If you can enable 9000-byte Jumbo frames on all devices involved in the data path, the upload speed becomes much healthier.
Download (from RPi4 server to a client): 2.05 Gbps
Upload (from a client to RPi4 server): 1.73 Gbps
USB multigigabit adapters
There are a few available on the market. After reading a dozen of reviews, I decided to get 3 adapters from a company called Sabrent. They make adapters with nice metal cases, which helps with dealing with the heat they dissipate.
Left to right: 2.5 GE USB 3.0 Sabrent NT-S25G, 5 GE USB 3.1 Sabrent NT-SS5G, 10 GE Thunderbolt 3 Sabrent TH-S3EA
The 5 GE USB 3.1 Sabrent NT-SS5G is the only I recommend for use with the RPi4:
It uses the Marvell Aquantia AQC111U chipset
It works out of the box with Raspberry Pi OS and
It works on Windows 10 after you install the driver
It ships with USB-C and USB-A cables so you can connect it to your laptop using USB-C or RPi4 using USB-A
Unlike other brands it does not overhead or disconnect due to instability
5 GE USB 3.1 Sabrent NT-SS5G ships with both USB-A and USB-C cables
ServeTheHome team did a great job of comparing the 5 GE adapters using the same chipset as the 5 GE USB 3.1 Sabrent NT-SS5G. It came out as a clear winner:
Why not use the cheaper 2.5 GE USB 3.0 Sabrent NT-S25G? Because it uses Realtek 8156 chipset, and there is no suitable Linux driver available at the time of writing.
Why not the 10 GE Thunderbolt 3 Sabrent TH-S3EA? Although it has a USB-C connector, it is not a USB adapter. It uses Thunderbolt 3 protocol, which is not supported by the RPi4.
I use RPi4 with PoE HAT, because it has a fan on it, and I power the unit by a USB-C charger. Both multigigabit adapters involved in the test are 5-Gigabit Ethernet capable Sabrent NT-SS5G. The best part is that these work out of the box on the Raspberry Pi OS with no action required on your part.
But, if you are considering the purchase of these adapters for your Mac, please stop. After you plug the adapter in, it uses Apple’s 1 Gigabit Ethernet adapter driver, and it would only auto-negotiate 1 Gbps. To enable 2.5 and 5 Gigabit speeds, and support for Jumbo frames on Mac, you have to disable Apple System Integrity Protection (SIP) tool, and install a legacy kext Sabrent driver. I would discourage you from making these security compromises. If you are interested in a multigigabit adapter that works with macOS out of the box, tune in later and read this review (link to be added).
How to increase the MTU and enable Jumbo frames?
On the Raspberry Pi:
sudo ip link set dev eth1 mtu 9000
On the Cisco Catalyst switch running IOS:
The RPi4 allows you to test download-only throughput up to 2 Gbps with standard MTU. Upload speeds are really poor and you would be better off using the built-in 1 Gibabit Ethernet adapter. You can use the RPi4 to run a few other tools, scripts, or take wall attenuation measurements.
With Jumbo frames enabled, 2 Gbps/1.7 Gbps is good enough for lab use or demonstrations. Keep in mind that you would have to enable Jumbo frames on all devices (RPi4, MacBook and the switch in my case).
The main cause of the relatively low performance is the storm of IRQ hammering the RPi4 CPU:
In a computer, an interrupt request (or IRQ) is a hardware signal sent to the processor that temporarily stops a running program and allows a special program, an interrupt handler, to run instead. Hardware interrupts are used to handle events such as receiving data from a modem or network card, key presses, or mouse movements.
If your use case requires a powerful iperf3 server, Apple’s Mac Mini with built-in 10 Gigabit Ethernet adapter would be something to consider today. It won’t be the cheapest option, but you won’t have to worry about performance or USB dongles. From what I’ve found, it uses Marvell AQC 1113 chipset and does 9.4 Gbps with 4 parallel iperf3 streams.
I purchased these adapters myself. No one asked me, or paid me, to write this blog post. I was as curious as you to see how the RPi4 performs when it comes to multigigabit Ethernet.
If you have followed my hot-swappable series, my goal was to find a solution to swapping multiple outdoor AP + antenna combinations and a variety of AP models on the same tripod. What is the use case? I only wanted to carry a single tripod on the site survey day while still having the flexibility to survey with variety of antennas and different AP models.
Please excuse the DYI approach. I did this during UK’s second COVID-19 lockdown. Shops were closed, access to tools was limited and I had no access to my lab.
How it turned out?
It went surprisingly well this time as I’ve already built a similar adapter for Cisco Meraki MR APs and this time it was even easier. Same as last time, the alu tube slides inside the top tripod tube and we are ready to roll.
The actual steps
I stocked up on M6 x 30 mm bolts, cut the 16 mm aluminium tube to the right length and reused the last bit of decking from a different project.
I thought I will try making a template, which I then transferred onto the wood. That wasn’t the best idea and it seems to work best when you watch someone using this “trick” on YouTube. Next time I will go for an analog pencil and ruler, lesson learned;-)
The decking is quite thick so I ended up shaving few millimeters off it. And here is the final adapter.
Thanks to Alan Wang, who suggested I use the official articulating pole mount AIR-ACC1530PMK2 and attach it to my “back board”. Obviously azimuth you can adjust by rotating the tripod, and this allow you to change the elevation angle.
This self-adhesive sleeve looks like a universal option, as it can be attached practically to any flat surface.
It has a silicone sleeve on one side and self-adhesive on the other.
The self-adhesive layer seems to be a good choice. It is not extremely sticky as some other products, it does not seem to leave marks, and I actually managed to remove the case from the Storm Box on our Tern GSD bike, move it to a more suitable spot and re-apply it.
It fits nicely inside the sleeve and as far as I can tell, there is no chance of it slipping out. The silicone keeps it from moving. In fact, it takes some effort to insert and remove the AirTag, which is great.
There are many accessories available for the GSD. Storm Box is a great candidate for an AirTag in this sleeve. Mine is still holding tight. It has a few internal pockets and you can easily attach a dozen of AirTags to it and still have some space left for more;-)
Bottom of the front rack might also be a good place for an AirTag.
A word of caution
Wherever you mount it, please keep your own safety in mind. Don’t mount it near the motor or anywhere near the chain/belt. It might cause you some bumpy ride should the self-adhesive fail.
Where can I buy one?
I bought mine on eBay and it was very affordable. Here is a link if you are considering getting one or two.
Other bike mounts
If you are looking for inspiration, I tested an under-seat and water bottle bike mounts. Here are a couple of photos and you can find more of them in the respective blog posts.
I’ve recently tested an under-saddle mount. On its own, it is an easy target and it can be easily found if the thief knows where to look. To make the most out of AirTags, I also have one inside my Storm Box.
To complement the two, I am now also using this AirTag mount, which can either sit between your water bottle and the bike frame. Alternatively, if you do not have a bottle, it can sit directly on the frame secured using the bottle holder bolts.
Let’s play hide and seek!
Here is where the GSD comes to the rescue. It has a couple of other mounting options with the exact same distance between the bolts as the water bottle bolts.
Note the two silver bolts inside the triangle on the right hand side. They can be used for this AirTag mount.
Assembly and installation
It is super easy to install. The original Tern screws are too short. So, let’s replace them with the 2 bolts supplied with the mount. The only tool you need is a standard hex head 3 mm screwdriver bit.
On Tern GSD Generation 2, you can choose between the upper or lower position. Personally, I prefer the upper one.
Where can I buy one?
I am in the UK and I purchased one on eBay. Here is the link if you want to check it out and get yours.
What other mounts are available?
I’ve also tested an under-saddle mount. You can see more photos of it and read more about it here.
If you ever experienced the helpless feeling of returning to an empty spot at the bike rack, you know how it feels when you realise that your bike has been stolen. I’ve been there twice. When Apple introduced AirTags, I thought that I should attach a couple to my bike and see how well they work. Here is my real-life test from iPhone SE user’s perspective if you are interested in the user experience and location accuracy.
AirTag does not come with any mount, let alone one suitable for bikes. So, I purchased a few and tested them.
This under-saddle mount caught my eye, and became my favourite.
Why/why not this mount?
Easy to install under your saddle – I tested it on Tern GSD Generation 2
You won’t notice it, unless you know what you are looking for
Ideal placement from Bluetooth radio perspective with not too many metal parts around it
It is 3D printed, which means that its surface is not 100% smooth. This is expected and nothing to worry about, considering the mount spends most of its life under the saddle.
Assembly and installation
Bolts are supplied with the mount. The only tool you need is a standard hex head 3 mm screwdriver bit.
Here is a tip for you: Remove the saddle from the bike, put it in between your thighs and install the mount. This makes it really easy with no bolts flying around.
Where can I buy one?
I am in the UK and I purchased it on eBay. Here is the link if you want to check it out and get yours.
As I mentioned, this mount is my favourite. Having said that, I recommend attaching another AirTag or two to your bike. I am testing a couple of other mounts and I will share the links here. Stay tuned, please.
I needed to find a solution to swapping multiple outdoor AP and antenna combinations on the same tripod. Specifically MR86 with MA-ANT-20 dipoles and MR86 with two MA-ANT-25 directional antennas. Quick swapping was a key requirement. Some coverage areas required directional pattern while other locations with low traffic and low client density would really benefit from omnidirectional coverage.
MRs ship with standard pole mounting hardware, which is great for permanent installation, but it didn’t allow fast swapping of the AP and antenna sets. Also, pole mounting kit requires tools, which is not practical as it add additional weight to your survey backpack.
Please excuse the DYI approach. I did this during UK’s second COVID-19 lockdown. Shops were closed, tools were limited and I had no access to my lab.
You are smart people, so I don’t need to stress this point, but please don’t take this write-up as Cisco’s official guide or recommendation. This is just me trying to find a solution to a problem.
So, what’s the solution?
Let me show you the final adapter and we can then look into the detail.
Under the hood
It all started when I spotted my wife’s aluminium 16 mm gardening tubes;-) I realised they were perfect fit for my tripod. They slide nicely inside the top tripod tube about a couple of inches (5 cm) or so.
What would I improve?
If I were to build a second iteration of this adapter, I would add a safety wire and attach the AP mounting bracket to the tripod. I would call this mandatory, especially if you are not the only user of these adapters or if there is going to be a person stood underneath the tripod.
Apart from that, it works really well, it is rock-solid, and allows me to swap the MR with omnis and MR with directional antennas in less than 10 seconds.
Many people are talking about the Ultra Wide Band (UWB) precision finding supported by AirTags and the last two generations of iPhones. It is possible thanks to Apple’s U1 chip. This feature on its own might quite likely be a good enough reason for many users to upgrade to the latest iPhone.
Since I don’t own iPhone 11 or 12, I was curious what the experience was from iPhone SE or XR user’s perspective. Due to the lack of the U1 chip, these phones don’t support UWB and “Precision Finding”. Instead, they use Bluetooth and “Proximity Finding”.
“With You” Bluetooth accuracy and audible alarm
When the tag is “With You”, that means that your iPhone or macOS device can hear the Bluetooth signal beaconed by the AirTag. In this mode, location accuracy seems to be around 10 meters (depending on where it is and if indoors or outdoors). The lack of the UWB support means that the SE or XR can’t detect the direction you or the AirTag is moving in.
Since the AirTags is “With You” (shown in the screenshot above) and is reachable via Bluetooth, you can activate the audible alarm and find its exact location this way.
Detached mode accuracy and refresh rate
When the AirTag becomes detached from your iPhone or macOS device (tag’s Bluetooth signal is lost), the tag then relies on other people’s iPhones and macOS devices. As soon as their device hears the Bluetooth signal of your lost AirTag, it relays (or reports if you will) the tag location to iCloud. Thanks to the crown-sourced relayed location, you will be able to see your tag’s current location in the Find My app although you are not anywhere the tag. The AirTag does not even have to be in the Lost Mode. Location finding works in its standard mode.
Location in the Find My does not update instantly. Based on my tests, it refreshes every 5 to 15 minutes.
When it comes to location accuracy relayed by other people’s iPhones and macOS devices, it ranges from approximately 10 meters to 110 meters.
Can Wi-Fi-only iPads relay location?
No, they can’t. I tested a couple of iPads connected to Wi-Fi with Bluetooth enabled and placed them in close proximity of the AirTag. They did not relay location. As far as I can tell, only iPhones and macOS devices can relay location of a tag.
Can cellular iPads relay location?
I don’t know. Please test it if you have one and tell me;-)
In the unfortunate event of losing your item, you can switch the tag to the “Lost mode” and receive a push notification whenever the AirTags gets automatically reported by someone’s iPhone or macOS device.
When that happens location, you receive a notification. Currently, there seems to be a cosmetic bug as the text of the notification does not show the latest location of the tag, but its previous location. When you open “Find My” app, you will see the correct and latest location though.
My test setup
iPhone SE 2nd generation running iOS 14.5
MacBook Pro running Big Sur 11.3.1
iPad Mini 5th generation running iOS 14.5
iPad Air 2nd generation running iOS 14.5
What is your experience with AirTags?
I am curious what your experience was. Have you tested any other scenarios? Have I missed anything. Please do let me know in the comments and I will update the post.