Running OpenWrt on Switches FAQ

At the time of this writing, there are a couple of switches that are supported by OpenWrt. All of them are based on a Realtek RTL83xx or RTL93xx SoC that features at least:

• 128MiB RAM (with the ZyXEL GS1900-24HPv1 and GS1900-24 being the only known devices with just 64MiB)
• 16MiB Flash (most of them 32MiB, but in a dual-firmware configuration)
• 500MHz MIPS CPU
• 8-52 GBit LAN ports

The hardware in these switches was designed for switching ethernet packets on L2. That means that the traffic does not pass through the CPU under normal circumstances, it is all handled by the switch fabric. While OpenWrt has all required packages available to turn them into routers, the performance is very low as the packets now need to pass the CPU.

In addition, the CPU does not have any optimizations for packet processing - something that router SoCs usually include.

You can expect about 20Mbit/s routing performance with such a switch being used as a router. The CPU interface of the switch is really only meant for running the configuration web interface.

Some Forum references:

• https://forum.openwrt.org/t/can-a-switch-become-a-router/159727
• https://forum.openwrt.org/t/solved-abysmal-speeds-in-a-realtek-rtl8380m-switch-zyxel-gs1900-8hp-v2/133894
• https://forum.openwrt.org/t/support-for-rtl838x-based-managed-switches/57875/478

There are still a number of valid reasons to run OpenWrt on the switch:

• You gain a unified configuration experience on all your devices powered by OpenWrt / LuCI
• You remove and eliminate anymost vendor-supplied binary firmware (the boot loader is usually not replaced and some firmware for the PHY is required)
• You liberate your device from any cloud management features
• You benefit from all OpenWrt security updates on a regular basis
• You have excellent documentation and support in the OpenWrt Wiki and Forum

Yes, there are a few drawbacks: There are some features that do not work or do not work properly (like link aggregation). Depending on the switch, some other features might be missing, check the commit message for your device and/or the wiki page for your device for details.

Some switches have limitations like:

• No support or limited support for the LED configuration (due to no driver support being available; e.g. TP-Link TL-SG2452P)
• Non-working SFP ports (due to no PHY driver being available; e.g. TP-Link TL-SG2452P)
• Not all SFP ports supported (due to limitations in the i2c driver; e.g. HPE JG927A)
• No support for PoE (due to no driver for the PoE controllers; e.g. ZyXEL GS1900-24EP)

while on other switches all of these features are supported.