How to Install OpenWRT on Linksys WRT1900ACS Router

The Linksys WRT1900ACS is a great router, but it can be even better with OpenWRT installed. OpenWRT is a free and open-source firmware that gives you more control over your router.

To install OpenWRT on your Linksys WRT1900ACS, you'll need to purchase a USB drive with a minimum of 8GB of storage space. The USB drive will be used to flash the OpenWRT firmware onto your router.

The Linksys WRT1900ACS has a factory reset button located on the back of the device. This button will be used to reset your router to its default settings.

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Before diving into the world of OpenWRT on your Linksys WRT1900ACS, it's essential to prepare your device. This involves backing up your current configuration and understanding the risks involved in flashing your router.

You should back up your current configuration to preserve your settings and internet connection.

The Linksys WRT1900ACS has a built-in backup feature that allows you to save your settings to a file.

Flash the OpenWRT firmware at your own risk, as it will erase all your settings and data.

Be aware that flashing the firmware will also reset the device to its factory settings.

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To download the OpenWrt firmware for your Linksys WRT1900ACS router, head to the Firmware downloads page of the OpenWrt Project. As of my writing, the current Stable Release was version 18.06.4, released on 1st July 2019.

Use the filter boxes to find the firmware for your router model and click on the ‘Firmware OpenWrt Install URL’ link to get the file. For example, I downloaded openwrt-18.06.4-mvebu-cortexa9-linksys-wrt1900acs-squashfs-factory.img.

Verify the downloaded firmware file using a checksum tool to ensure it's correct and won't brick your device. To do this, retrieve the reference checksum from the root folder of the download URL and compare it with the SHA 256 checksum of your downloaded file.

Once verified, upload the firmware by navigating to the Connectivity section and locating the Router Firmware Update section. Click on the Choose File button, select the firmware image, and hit Start to begin the installation process.

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Before you start the process, it's essential to check your router version because firmwares are not compatible between hardware versions.

To do this, locate the hardware version beside or beneath the model number on your router, it's usually labeled as "version", "ver.", or "V."

If you can't find the version number, it's likely that your device is version 1.

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To download the firmware, head to the Firmware downloads page of the OpenWrt Project. The current Stable Release at the time of writing was version 18.06.4, released on 1st July 2019.

Use the filter boxes to find the firmware for your router model and click on the ‘Firmware OpenWrt Install URL’ link. I had to do this to find the firmware for my Linksys WRT1900ACS.

The firmware image you download will have a long filename, like openwrt-18.06.4-mvebu-cortexa9-linksys-wrt1900acs-squashfs-factory.img. Make a note of this filename for later use.

After downloading the firmware image, verify it using a checksum tool to ensure it's correct and won't brick your device. This involves retrieving the reference checksum from the download site's root folder and comparing it to the checksum generated by the tool.

The reference checksum for my download was 4c2dfe16b427df50c2e7bd6753d82ea944bc0925c1cf25488ab42a1d9ba43839. If your checksums match, you can proceed with flashing the firmware.

Installing OpenWRT on your Linksys WRT1900ACS is a straightforward process that requires some basic steps. Download the latest, stable OpenWRT release for the router from the provided table, making sure to download from the "Firmware OpenWRT Install URL" column.

To begin, power up the router. Next, configure your Ethernet card with a static IP address of 192.168.1.2. This step varies depending on your operating system, so consult The Internet if you're unsure.

Connect your computer and the router with an Ethernet cable, using any of the 4 blue Ethernet ports on the back of the router. Avoid the yellow port marked with "Internet." Now, open the Linksys router administration interface in a web browser, accessing it at the default IP address of 192.168.1.1.

The router will complain about a lack of internet connection, but this is normal. Log in with the password "admin" to proceed. After logging in, take a moment to examine the Linksys administration interface, which will soon be replaced by the OpenWRT experience.

To initiate the installation, click on "Connectivity" in the left-hand menu, then select "Manual" and choose the OpenWRT firmware install package you downloaded earlier. Click "Start" and confirm with "Yes" on the warning prompt. The flashing process will begin, so be patient and avoid powering off the router or disconnecting it from your computer.

Here's a step-by-step summary of the installation process:

You'll see a notification that the administrator's root password is not set when you first log in to your OpenWrt Linksys WRT1900ACS.

Just log in with the username of root and leave the password field empty for now.

Once you've logged in, you'll see a page where you can set the root password. This is a crucial step, as the root account is extremely powerful and requires a strong password that you'll remember.

Fill the 'Password' and 'Confirmation' fields with a secure password and click on the 'Save & Apply' button to complete the setup.

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You'll see a notification that the administrator's root password is not set.

In this case, just log in with the username of root and leave the password field empty.

As you log in, you'll see a page where you can set the root password, which is the username of the administrative user in OpenWrt.

The root password is extremely powerful, so it's essential to provide a strong password that you'll remember.

Fill the 'Password' and 'Confirmation' fields with a strong password, and then click on the 'Save & Apply' button to complete the setup.

To turn on WiFi on your router, you need to go to the Wireless configuration page by selecting the “Network > Wireless” menu option at the top of the page.

You'll then click the ‘Edit‘ button on the wireless network you want to enable. The Wireless Overview page contains information related to the physical radios in the router that handle Wi-Fi communication.

To set up the network security, click on the ‘Wireless Security‘ tab of the ‘Interface Configuration’ section. Select an Encryption method, such as “WPA2-PSK”, which is recommended for home/small office networks.

Choose a Cipher, and “auto” is a good option. Enter a Key, a secret phrase to connect to your WiFi network, and make sure it's at least eight characters long for WPA2-PSK.

Additional reading: Openwrt Travel Router