Many users are familiar with the situation where their primary router can't penetrate thick walls or is too far from their workstation. Instead of purchasing expensive mesh systems or new routers, it's often possible to revive an old device by turning it into a signal booster. Mi Router 4C Initially positioned as a budget solution, thanks to the MediaTek MT7628AN chipset, it became a real hit among enthusiasts who want maximum functionality for pennies.
Unfortunately, Xiaomi's stock firmware doesn't offer a built-in Repeater or Bridge feature as the end user would understand it. However, this limitation can easily be circumvented by installing alternative software. In this article, we'll cover in detail how to reflash the device and configure it to extend the range of your wireless network.
You don't need to be a certified network engineer to perform this procedure, but you will need to be attentive. The process involves working with the command line and downloading specialized software. The result will be stable network operation where previously there was only a "dead" signal, and the router itself will no longer be a dust collector.
Technical features and limitations of the 4C model
Before starting modification, it is necessary to clearly understand what kind of hardware we are dealing with. Mi Router 4C It's based on a MediaTek MT7628AN processor, which supports 2.4 GHz and the 802.11n standard. This chip is dual-band only in theory (2T2R support), but in this implementation, antennas are often soldered in a way that limits speed.
A critical parameter is the amount of RAM. This model has only 64 MB of RAM. By comparison, modern entry-level routers often have 128 MB or 256 MB. This means that heavy software packages, such as a full-fledged OpenWrt with the LuCI graphical interface and many plugins, may work unstable or require careful optimization.
⚠️ Caution: The Mi 4C's internal casing is often sealed with hot glue or has non-standard screws under the stickers. When opening the casing to connect the UART cable, there is a high risk of damaging the plastic casing latches.
Despite its modest specifications, the MT7628AN chipset provides excellent driver support for both client and repeater modes. The main limitation here isn't processor power, but rather memory capacity, which dictates the firmware version you choose. You'll have to choose between functionality and system stability.
Preparing for Flashing: Choosing an OpenWrt Version
Since the stock functionality doesn't allow you to configure repeater mode, the only viable option is to install a third-party OS. For devices with 64 MB of memory, the standard image may be too heavy. There are two main options: installing a lightweight version of OpenWrt or using specialized builds, such as Padavan, if they're tailored to the specific board revision.
For the Mi Router 4C, the most stable solution is OpenWrt version 19.07 or the newer optimized builds 21.02, specifically compiled with a minimal set of packages. You need to find the firmware file with the extension .bin, which is marked as compatible with ram64 or specifically for mi-router-4c.
Before starting any work, make sure you've identified the exact revision of your device. The model number may be listed on the sticker on the bottom, but different circuit boards may be inside. Checking the firmware via the web interface or Telnet (if available) will help prevent bricking. Download the firmware file only from trusted sources, such as the official OpenWrt repository or the 4PDA forums.
Why OpenWrt?
OpenWrt isn't just firmware, but a fully-fledged Linux-based operating system. It allows you to transform a low-cost device into a professional networking tool, adding features that manufacturers often block or omit for marketing reasons.
The process of installing alternative firmware
The safest method for updating the Mi Router 4C firmware is to use the built-in update mechanism if the firmware version allows manual file uploads. In some regions, routers come with the global version, while in others, they come with the Chinese version. Chinese versions often have protection against third-party software installation, which must be bypassed via Telnet or special exploits.
If you have successfully accessed the web interface with administrator rights, the process is as follows. Go to the section Status → System → Backup / Firmware Upgrade (The path may vary depending on the version). Upload the previously downloaded file. openwrt-...-mi_router-4c-squashfs-sysupgrade.bin.
☑️ Checklist before flashing
After the file is downloaded, the recording process will begin. The router's indicator light will start flashing. Do not unplug the power cord during this process. The process takes approximately 2-3 minutes. If the router still doesn't establish network connectivity after rebooting, you may need to perform a factory reset (hold the Reset button for 10 seconds while the router is powered on) or flash the firmware via UART.
If the standard method doesn't work, you'll have to resort to TFTP recovery or disassembling the device to connect the UART console. This requires a USB-TTL adapter and soldering skills. For most users, finding a vulnerability in the web interface of a specific firmware version that allows a file to be uploaded without signature verification is sufficient.
Setting up repeater mode (Relayed)
After successfully installing OpenWrt, you'll have a clean system. To turn your router into a repeater, you need to properly configure the network interfaces. Unlike "Client" mode, which simply distributes internet via cable, we need to broadcast the Wi-Fi signal further. For this, OpenWrt uses the [programming] package. relayd or setting up a bridge between WAN and LAN.
The first step is to connect to the new router's Wi-Fi network (usually called OpenWrt) and log in to the address 192.168.1.1. You need to go to the menu Network → WirelessHere you'll see two interfaces: one for the access point (AP) and one for the client. In Client mode, click the "Scan" button, find your primary network, and connect to it by entering the password.
Next, you need to create a bridge. Go to Network → InterfacesCreate a new interface or edit an existing LAN. In the "Physical Settings" field, make sure both interfaces are selected: the built-in LAN and the wireless client (e.g. br-lan including radio0 And sta). This will combine the ports and Wi-Fi into a single network.
| Parameter | Value for Main Router | Meaning for Mi 4C (Repeater) |
|---|---|---|
| IP address | 192.168.1.1 | 192.168.1.2 (static) |
| Gateway | - | 192.168.1.1 |
| DNS | Provider / 8.8.8.8 | 192.168.1.1 |
| Wi-Fi mode | Access Point | Client + Access Point |
It's important to change the IP address of the Mi Router 4C itself so it doesn't conflict with the main router. If the main router has an address of 192.168.1.1, then our repeater should be set to, for example, 192.168.1.254. This should be done in the LAN interface settings by changing the protocol from DHCP to Static and entering the address manually.
Optimizing wireless network and channels
After setting up a basic connection, speed drops often occur. This is because the Mi 4C has only one radio channel, and it can't simultaneously receive and transmit data at full speed (half-duplex). To minimize losses, it's important to properly configure the channel width.
In the wireless interface settings (Network → Wireless → Edit → Advanced Settings) try changing the channel width. If the broadcast is very noisy, setting the value 20 MHz instead of Auto or 40 MHz This can improve connection stability, although it will reduce the theoretical maximum speed. You can use built-in tools or smartphone apps to monitor channel congestion.
It's also worth paying attention to the transmission power. In the section Advanced Settings there is a parameter Transmit PowerIt doesn't always make sense to crank it up to maximum (20 dBm or 100%). Sometimes reducing the power to 15-17 dBm reduces errors and chip overheating, which positively impacts overall throughput.
⚠️ Note: Interfaces and menu item names in OpenWrt may differ depending on the installed theme (LuCI) and kernel version. Always consult the documentation for your specific version.
Solving typical problems and diagnostics
During operation, situations may arise where the network is available, but the internet is not working. Most often, the problem lies with the DNS or the incorrect gateway. Check that the DNS server address is specified in the WAN interface settings (or in the global DHCP settings). You can use public DNS from Google (8.8.8.8) or Cloudflare (1.1.1.1).
If devices aren't receiving IP addresses, make sure the DHCP server is disabled on the Mi Router 4C. In repeater mode, only the main router should distribute addresses. Check this in the section Network → Interfaces → LAN → DHCP Server, where the "Ignore" or "Disable" checkbox should be.
For advanced users, a diagnostic tool is available via the command line (SSH). The command logread will show system logs where you can find connection errors to the main router. The command wifi status, which will show the current state of wireless interfaces.
Frequently Asked Questions (FAQ)
Is it possible to use Mi Router 4C as a repeater without flashing the firmware?
The official Xiaomi firmware does not support Repeater or Bridge mode for this model. The device can only function as an Access Point if connected to the main router via a cable. For Wi-Fi operation without a cable, you need to install OpenWrt or Padavan.
What is the maximum speed through this repeater?
Because a single radio module is used for both reception and transmission, the actual speed via a Wi-Fi repeater will be approximately 40-50% of the speed achieved by the 4C router itself. Given the limitations of the 802.11n standard and the 2.4 GHz channel, you can expect 15-25 Mbps under ideal conditions.
Will the warranty be voided if I flash the firmware?
Yes, installing third-party software automatically voids the manufacturer's warranty. Furthermore, there's a risk of bricking your device if you interrupt the flashing process or use an incorrect firmware file.
Do I need internet access to configure OpenWrt?
No, the OpenWrt operating system itself runs autonomously. However, for the initial package installation, database updates, and time settings, you will need an internet connection, which the router will receive through the main router.