Linksys MX4200: A £40 OpenWrt Powerhouse

In my previous post, In search of the perfect OpenWrt router, I discussed my potential future router. When I started researching it more thoroughly, I paused purchasing the Brume 2 and tried to think of what would be better.

I looked into the Brume 2 when I began researching a potential change of broadband provider from Virgin Media to a full (synchronous) fibre connection (CityFibre).

With the provider (reseller) that I am currently considering (Toob), a 900/900Mbps connection offered the best value for money (£25 per month with no price increases over the whole contract period). However, to achieve that speed, they need to provide me with the right hardware.

I’ve noticed that most resellers of CityFibre services utilise Linksys devices, particularly the MX4200 in its second version (v2). This model is sometimes branded as the Linksys Velop MX4200 (AX4200) or ISP-branded as the Linksys SPNMX42, which is simply a v2 in disguise. However, Linksys has already discontinued this device.

There is a problem identifying which MX4200 is version 1 and which is version 2. The v2 is the only one I’m considering, due to its 1GB of RAM, instead of 512MB in v1. The easiest way to identify v1 from v2 is by looking at the dimensions of the devices themselves. If your device is around 24.3cm (9.57 inches) high and 11cm (4.45 inches) wide, it’s a v2 (buy). If it is 18.5cm (7.3 inches) high and 7.9cm (3.1 inches) wide, it’s a v1 (don’t buy).

The Brume 2 initially appealed to me with its 2.5 Gbit WAN port, 1GB of DDR4 RAM, 8GB of eMMC storage, and a USB 3.0 port. The downside, however, was a limited number of LAN ports, which would require me to purchase a network switch to connect all my devices correctly.

The Linksys MX4200, despite having four Gigabit ports (one WAN and three LAN), also features a quad-core processor (1.4GHz). Compared to the dual-core 1.3GHz processor on the Brume 2, this offers a better starting point for handling such demanding internet connection speeds.

I’ve also been concerned about the small dimensions of the Brume 2 device itself and its enclosure, which I believe won’t provide sufficient heat exchange for proper cooling. I’ve read through some online discussions where people mentioned that this device tends to get hot, and when it does, performance, especially network traffic, drops.

This made me ponder. I also started asking myself: do I actually need a 2.5 Gbit port? None of the devices from other resellers that provide connections near 1 Gbps utilise a 2.5 Gbit WAN port, as they don’t see the benefit of it, arguing it only generates additional manufacturing costs.

I’ve indulged myself in digging out information regarding whether a Gigabit WAN port is sufficient for a 900/900Mbps connection, and all evidence points to yes.

• Gigabit Ethernet Throughput: A Gigabit Ethernet port has a theoretical maximum speed of 1000 Mbps.
• Overheads: Network protocols have some overhead (data used for managing the connection, error checking, etc.). This means you’ll never quite achieve the full 1000 Mbps for actual data transfer.
• Real-World Speeds: For a 900/900 Mbps connection, a Gigabit WAN port is typically sufficient to deliver close to those advertised speeds. You might see variations (e.g., in the 850-950 Mbps range) due to these overheads and other factors like your computer’s capabilities, the server you’re connecting to, and general network congestion. This is normal.

A 2.5 Gbit WAN port would offer more headroom and could potentially allow you to consistently achieve speeds slightly above 900 Mbps if your service delivers that. However, for a service advertised as 900/900 Mbps, a Gigabit port is well-matched and shouldn’t be a bottleneck preventing you from getting the speeds you’re paying for.

Essentially, while 900 Mbps is close to the practical limit of a 1000 Mbps Gigabit port, it’s still well within its capability to deliver those speeds effectively. Internet Service Providers (ISPs) supply routers with Gigabit WAN ports for these plans because they are adequate.

Considering all the above from my research, I’ve abandoned the idea that my next router “needs” to have a 2.5 Gbit port (at least for now).

I did some further research into processors, especially comparing the Qualcomm IPQ8174, used in the MX4200, and the MediaTek MT7981B (Filogic 820), used in the Brume 2. I’ve concluded that the Qualcomm will perform well, and the design of its device will be much better at maintaining performance under stress (heat).

When comparing the Qualcomm IPQ8174 and the MediaTek MT7981B for use in a router handling a 900/900 Mbps internet connection, I delved into the specifications of both processors.

Each of these processors utilises its own solution to improve traffic, thanks to hardware offloading capabilities. The main differences will become apparent in CPU-intensive tasks beyond simple NAT and forwarding, and in their general CPU headroom.

The Qualcomm IPQ8174 offers a Qualcomm Packet Processing Engine (PPE), a security engine, and other network acceleration features.

The MediaTek MT7981B (Filogic 820) offers MediaTek HNAT (Hardware Network Address Translation), HQoS (Hardware Quality of Service), an NPU (Network Processing Unit), and MediaTek FastPath™.

Both chips rely heavily on their respective hardware engines to accelerate packet forwarding and NAT. This means the main CPU cores are largely bypassed for these routine tasks, allowing for high speeds with low CPU utilisation.

• The MT7981B is explicitly designed for multi-gigabit routing (often found in devices with 2.5GbE ports), and its HNAT/NPU is very effective.
• The IPQ8174, as part of Qualcomm’s “Networking Pro” family lineage, also has robust packet processing engines capable of gigabit-plus speeds.

However, remember that not all options for hardware implementations are, or will be, implemented into OpenWrt.

At 900/900 Mbps with offloading active, CPU utilisation on the main cores should be relatively low for both. This is crucial as it leaves CPU resources available for other tasks the router might be performing.

Both are suitable, and you should achieve your full connection speed for typical internet use, assuming well-optimised firmware is used. For that purpose, I will be using pure OpenWrt, rather than the firmware provided with the devices by manufacturers.

If you look at the Raw CPU Power, the Qualcomm IPQ8174 has a clear advantage with its quad-core A53 configuration at 1.4 GHz compared to the MT7981B’s dual-core A53 at 1.3 GHz. This equates to approximately double the general-purpose multi-core CPU processing capability.

I am planning to maintain my VPN (either WireGuard or through Cloudflare Zero Trust). Hence, the number of cores (CPU overhead) will hugely impact the speeds that can be achieved through the tunnel.

The IPQ8174’s extra cores and slightly higher clock speed will provide significantly better performance. Encrypting and decrypting VPN traffic is CPU-intensive and often cannot be fully offloaded in the same way as basic NAT.

Overall, the IPQ8174 would handle more demanding shaping tasks with less performance impact.

My router also has other services added, so I will need to consider a better processor if I want to adopt a future-proof approach. The extra CPU power of the IPQ8174 provides more headroom for future firmware updates that might introduce new features, or if my usage pattern becomes more hardware-demanding.

Both processors are based on ARM64 architecture (ARMv8), backwards compatible to run 32-bit software where needed.

Given the CPU-intensive services I plan to run, the decision to go with the MX4200 is the stronger choice.

Personally, I would prefer to go with the MX4300, due to its doubled storage and RAM; however, I’m struggling to find it available in the UK marketplace, and importing from the US is impossible due to very high shipping costs.

Also, the Linksys MX4200, due to its wide availability on eBay (as branded through different providers), will allow me to acquire it for around £40 as a starting point, which is another benefit over the Brume 2.

I personally suggest buying the non-branded Linksys Velop MX4200, which can be purchased starting from £40 at CeX. If you opt for branded ones, be careful, as most of them are not easy to unlock and install clean OpenWrt. The one that is somewhat manageable is from Community Fibre, though it may not always be straightforward.

The Brume 2 does not have any Wi-Fi capabilities, which I don’t mind as I utilise an external Access Point for that. However, for other people, having an all-in-one solution like the Linksys MX4200 will be a no-brainer.

Reminder: If you decide to go with the MX4200, always make sure to purchase the second version (v2). Ask the seller and compare the dimensions between v1 and v2 to avoid disappointment later. Many v2 devices do not even state this on the label. Mine, however, arrived with ‘V2’ clearly stated after the model number on the bottom label. The dimensions, however, will tell you a bit more.

The Downgrade

Linksys devices are a bit different from other brands due to their dual flash capability. Effectively, the device has two partitions for firmware. This is important during the initial flash of squashfs-factory.bin. Once you’ve installed your initial firmware and successfully run the device from OpenWrt, you need to remember to follow additional steps and repeat the flashing with squashfs-factory.bin on the second flash partition. If you do not do this, your router will not run after the next OpenWrt firmware upgrade, which is performed using a round-robin logic, and subsequent reboot. You will then need to perform a power cycle method to manually switch to the partition on which OpenWrt was initially run.

For that purpose, it’s important to follow the Flash OpenWrt to Alternate Partition step. This involves checking which partition OpenWrt is currently running from, sending squashfs-factory.bin to the router using the SCP protocol (or wget if you have internet access on the device), and then flashing it to the other partition. Luckily, you only need to do this once.

Dual flash does offer a benefit: you can prepare working software on both partitions. If something goes wrong with the initial partition, you can simply switch over and boot the router from the alternative one.

However, dual flash also comes at a cost. The storage available on the MX4200, which is 512MB NAND, will be halved. Each firmware installation will only have half of the total storage available for data.

This means your disk space (Storage) available on your router will effectively be around 110MB for applications that you wish to install.

Comparing this to my single-flash router, the Askey RT4230W REV6 (RAC2V1K) from Spectrum (imported from the US), which I repurposed with OpenWrt, I have almost 354MB of storage available for my applications.

This implies that, by upgrading my router to newer technology (processor), I am getting a third of the storage. This is precisely why the MX4300 model would be much better to purchase, if available in the UK.

Luckily, on my current router, I am only using slightly over 42MB of storage. Hence, 110MB available in total will not be an issue for now, but it would be better to have some room for future needs.

From the discussion on my other post, some people suggested looking into NanoPi. If I were to go down this route, I would currently only consider the NanoPi R6S due to its superiority in every aspect, also providing, by default, three LAN ports (one native Gigabit Ethernet and two PCIe 2.5G Ethernet, each over separately designed network chips).

If you’re looking for a budget-friendly option for use in your home network, consider a second-hand Linksys MX4200, to which you will change the firmware from Linksys to pure OpenWrt.

If money is not a problem, or you require much more processing power, especially in a business environment, then the NanoPi R6S is the device you should consider. This is particularly relevant as it’s also natively supported by the latest OpenWrt.