What's “flashing firmware” anyway?
In short, flashing is installing new firmware. On a device like a router, firmware is most of the basic programming code which runs most of the major functions on the device. This is similar to the installed operating system and programs on a PC. Similar to a PC, firmware updates are released to fix bugs, add new features, and increase security. The device can usually run without updates in a fairly stable way. However, you should understand the risks this may involve for your network.
Firmware is “firm” because we don't apply changes or updates nearly so often. It's a bigger event to flash firmware than it is to to update software. This is because the Flash RAM memory which stores router firmware isn't designed to be written to frequently. As well, more things can go wrong during firmware flashing.
Flashing firmware is usually done to fix bugs, improve stability or add new features to the device. In the case of FreshTomato, the firmware often adds all of the above when compared with the vendor's “stock” (original) firmware.
On routers, firmware is stored in a type of non-volatile memory called Flash RAM. The contents of non-volatile memory such as Flash RAM remain after reboots or when the device is turned off. If they were erased, the device would not function. On routers, firmware is replaced or updated by uploading the entire image of the operating system installation and its programs to an EEPROM (electrically erasable and writable) chip.
Again, this is vaguely similar to reformatting and reinstalling the entire operating system on a PC. However, during the firmware flashing process, files are not copied one at a time onto a filesystem. Instead, one single image file of the entire installation is copied to Flash RAM, a small portion at a time. This is similar to using a drive imaging program such as Acronis TrueImage for Windows, or Time Machine for the Macintosh.
We refer to the files used to flash FreshTomato as “image” files, because they are mirror images of the entire installation of the operating system programs. The flashing simply copies the entire image file to the router's Flash RAM.
A build is one compilation of firmware.
Each build is:
The features included depend on the router's hardware and on which build/version is flashed. See the Feature matrix page for details on which features are included in each build).
Make sure to carefully choose a FreshTomato build appropriate for your hardware model. Choosing the wrong build/version could brick your router if it's not appropriate for your hardware. (See bricking section below).
When choosing a build, you need to make note of:
Some hardware models have two or more hardware versions/revisions. Some of these may contain different chipsets than others. Flashing the firmware to the “same” model hardware, but wrong version or revision could brick your hardware.
For some models, Flash RAM is limited, so it’s also important you choose a build that takes up less storage space than is available. Otherwise, you could run out of Flash RAM and your hardware could be bricked. For help choosing a build that's appropriate for your hardware, see the Hardware compatibility wiki page. For more guidance on how to choose a build, see the How Do I Choose a Build? section on the FAQ page. If you're still unsure after you've read both those pages, we recommend you ask for advice on the Tomato forum.
“Bricking” mean making your router completely non-functional after a failed flash. It's called bricking because the hardware would then only be useful as a brick, but not as a router. In this condition, It often can't be fixed without electronics or soldering knowledge.
Here are some rules for successful firmware flashing:
Doing any of the above can result in a partial update. This may leave the firmware corrupted, which can damage how the device works or even “brick it”, making it useless.
NVRAM is the part of non-volatile memory in routers where settings and parameters are stored.
FreshTomato can sometimes retain some NVRAM variables (settings) even after you flash a new firmware image to your router. Therefore, it's very important to erase NVRAM before flashing. Doing so ensures that all variables from the existing firmware are erased before flashing begins. Erasing NVRAM before flashing is an important step that should NEVER be skipped.
A “dirty flash” is a flash which was performed without thoroughly wiping NVRAM before and after flashing. A dirty flash often leads to strange, unexplained symptoms, like web interface pages that don't display properly, “missing” menu items, and just generally buggy or unstable functioning. No matter how tempted you are to “save time”, please don't do a dirty flash. You will likely waste time with strange symptoms and regret your choice.
There are several methods used to flash firmware on modern routers. The method you use depends on several things.
For Asus hardware, several methods/tools are available for firmware flashing.
In general, if your (FreshTomato supported) Asus hardware has a version of FreshTomato installed, or another Tomato fork, such as Shibby or Toastman, you can upgrade straight to FreshTomato using the Upgrade menu.
This flashing method is only possible for builds of release 2022.3 and later. In this example, we will flash an RT-AC68U model.
Here are the steps to follow:
Asus provides a Windows program called Firmware Restoration. This utility is used to flash firmware or recover from a failed firmware flash. It finds the router's IP address and lets you flash firmware to the router, after you've put the router into Rescue Mode. Rescue Mode is a mode in which the router won't do anything except receive a firmware update.
For Asus models built in or before 2014, the Firmware Restoration utility will work fine. However, on most Asus models after 2014, Firmware Restoration will not let you flash third-party firmware like FreshTomato. If you try this on newer hardware, the program will simply throw an error saying it's not possible.The reasons indirectly relate to a 2015 decision made by the US FCC (Federal Communications Commission) about changes to wireless features in third-party firmware. For details, see the section below titled: FCC Regulation Change Affecting Wireless Routers.
To flash using the Firmware Restoration utility:
At this point, the router should function properly.
Sometimes on the first boot after flashing, FreshTomato may seem buggy or strange things may happen.
In such cases:
If problems persist, try the following:
If the router is still acting strangely at that point, it is advised that you request help on the Tomato Web forum.
“Trivial File Transfer Protocol” is a small utility for transferring files between hosts on a TCP/IP network. It lets you upload firmware images to a router. There are command-line and graphical tftp client programs available. Windows includes a tftp program for the command line.
The TFTP method is useful when the manufacturer's firmware blocks other methods of upgrade from the stock (original) firmware.
To prepare to flash via tftp:
“tftp –I PUT filename.trx <IP address of router>“
but DO NOT press Enter.Note that Rescue Mode has a timeout period, so there is a limit as to how long you have to upload the firmware. If the timeout period expires, you may need to put the hardware into Rescue Mode again and restart the flashing process.
If your hardware has a fork of Tomato already installed, you can simply use the Administration/Upgrade menu in Tomato's web interface to upgrade to FreshTomato.
Flashing Linksys hardware can, in some cases, be a little more complicated than flashing other brands of hardware. It is recommended that you first check the Notes section of the Hardware compatibility list for important details before flashing. This section includes warnings about important issues such as NVRAM sizes/limitations, CFE modifications which might be required, hardware revisions and more.
Some models might need to be flashed with a special “initial” firmware build first before you can install a regular FreshTomato build. Please read about this above before installing FreshTomato.
There are no official wiki HOWTOs for flashing Linksys hardware. However, there are several unofficial HOWTOs on the Tomato forum which have been used successfully many times:
How to flash Linksys EA6300v1, EA6400, EA6500v2, EA6700, EA6900v1.0/1.1 with Tomato
If you you are still not sure how to proceed, it is recommended that you post an inquiry on the Tomato forum to avoid problems.
You are also advised to read the Notes section at the bottom of this page for more details on general flashing basics.
If you have a Netgear R-series router with Netgear firmware installed, you must first flash with one of the “Netgear R-series initial” files. Once you have an R-series initial FreshTomato build installed, you can then upgrade FreshTomato to newer versions using regular build files. The initial .zip file contains a firmware file with a .chk file extension. The original Netgear firmware can use that file to install FreshTomato.
As an example, the following steps review the process for flashing an R7000 with an initial build, and then a normal build.
First, download the two files you'll need to flash the R7000:
The “R-series initial file” for R7000:
This .zip file has the following MD5SUM value: ec63c869fe14f5b46cbb13813c1699bf
The normal R7000 AIO build file:
This .zip file has the following MD5SUM value: ec63c869fe14f5b46cbb13813c1699bf
Verify integrity of both .zip files by running a hash check program against them. On Windows, HashMyFiles works well.
If the MD5 has found in the hash check program matches the number listed above, the file is good. If it does not match the value above, the file has been corrupted during download and should be downloaded again. Do not flash using the contents of .zip files that fail a hash check.
Now, unzip the .zip files. The two files inside should look like this (for this particular router model/release of FreshTomato).
freshtomato-R7000-2023.2-initial-64K.chk
freshtomato-R7000-ARM-2023.2-AIO-64K.trx
If you're not sure which build file to download,
In the case of the R7000, the data in the table describe these specifications:
Now, let's perform the flash procedure:
If you already have FreshTomato installed on your Netgear, you can upgrade to newer releases using regular build files. These .zip files contain firmware files ending with the .trx file extension.
A Netgear router with FreshTomato installed cannot be directly flashed back to original Netgear firmware with normal builds. Some Netgear models can be flashed back to Netgear firmware using special builds called “Netgear back to OFW” builds. You can check if your Netgear model is supported in the “Netgear Back to OFW” folder in the appropriate FreshTomato downloads folder:
Starting in 2015, The US FCC (Federal Communications Commission) passed legislation designed to block people from changing certain Wi-Fi settings, to avoid creating radio interference with other devices. Wi-Fi radio power had to be implemented in hardware so end users could not modify it. For example, the FCC wanted to make sure end users didn't override country settings or power limits.
Some hardware vendors reacted to the legislation in an extreme way, blocking third-party firmware from being flashed entirely. It's important to note that FCC did not require anything like this. Some companies' hardware could not be flashed with third-party firmware from within the interface of the stock firmware. If you tried to do so, you'd simply receive an error stating it wasn't possible. This resulted in a lot of controversy.
ArsTechnica.com: FCC: Open source router software is still legal under certain conditions:
https://arstechnica.com/information-technology/2015/09/fcc-open-source-router-software-is-still-legal-under-certain-conditions/
SLATE: FCC Support for hackable routers is a win for all of us:
https://slate.com/technology/2016/08/fcc-support-for-hackable-wireless-routers-is-a-win-for-all-of-us.html