This tutorial explains how I successfully re-flashed my Linksys WRT54GL version 1.1 to use the Tomato 1.22 firmware rather than dd-wrt version 23 SP2 VPN firmware (generic) I have been using for the past couple of years. I decided to write this tutorial because lots of sites have instructions on flashing from the default Linksys firmware to Tomato but far fewer sites offer lots of detail on how to flash from other firmware such as dd-wrt.

I have provided directions with enough detail for the non-technical user to feel comfortable with the procedure. To make things faster for the technical users, I have highlighted the major steps. At the bottom of the post, I’ve included links to related articles I’ve published if you’d like to learn more.

As a bit of background information, I’m used a fully patched (as of November, 2008) Windows Vista Ultimate 64-bit with Service Pack 1 (SP1) Operating System and up-to-date Firefox 3 during the firmware upgrade process. The OS and web browser shouldn’t matter that much, but I thought I share in case you were worried about such things.

Before you begin, download the latest version of the Tomato firmware that is suited for most routers. This tutorial walks through flashing to version 1.22. The files are zipped in the great, but uncommon, 7zip format so you’ll need 7zip or another program that supports the 7zip format to unzip the files. The zip package contains several files, you will only need the “WRT54G_WRT54GL.bin” file but it is a good idea to checkout the “readme.”

I recommend verifying the MD5SUM hash of the “WRT54G_WRT54GL.bin” file to ensure the download wasn’t corrupt or hasn’t been comprised. If you don’t already have a tool to calculate MD5SUMs, I recommend using HashCalc although you must manually compare the sums with this tool unlike some other tools. Unfortunately, Polarcloud does not provide the MD5SUM of the download on their site but luckily for you, I calculated the hash of my download. The signature of the file should be 866251021d42608c69bff558115f95f8.

I recommend printing (or at least saving, not bookmarking, to your hard drive) the following web pages for reference since you will not have Internet access during this process:

• How to Change Your WRT54GL Firmware from DD-WRT to Tomato
• Tomato FAQ
• Tomato Firmware Wikibook
• Reset and Reboot
• Recover from a Bad Flash

It is best to turn off your firewall and anti-virus during this process to ensure that nothing interrupts the firmware flash. An interruption could cause the flash to fail and brick your router. If something does go wrong you may be able to recover from a bad flash.

You should ONLY perform the flash through an Ethernet cable using standard http (not https). Do not do this wirelessly (its best to temporarily disable the wireless adapter on your computer). If your super paranoid or live in an area with unreliable electricity, you should plug your router an PC into an uninterruptible power supply because a power failure during a firmware flash could brick your router. Plug the blue Ethernet (Cat5/RJ45) cable that came with your router into the Network Interface Card (NIC) on the back of your computer and into one of the ports labeled 1, 2, 3, or 4. The “Internet” port on your router should be connected to your broadband source (e.g., cable or DSL modem). Please ignore the extra cable in the picture. It is not needed for the flash to work.

I recommend reviewing all of your dd-wrt settings so you can quickly configure the Tomato firmware to offer similar functionality. I took screenshots of all of the pages where I had non-default settings. I also used the same security settings, including WPA2 password, after I loaded Tomato so that all of my wireless devices would not have to be updated. However, if you have poor wireless security, after flashing to Tomato is the perfect time to implement stronger security. You can reference my Securing Your Wireless Network article if you want to learn how to have a really secure wireless network.

In addition to the screenshots of your settings, it is also a good idea to perform a backup of your dd-wrt configuration. Please note you can only restore this backup on the same model router and firmware with which the backup was made. To perform a backup, go to the “Administration” tab and then the “Backup” sub-tab. Once there, just click the “Backup” button and save the file.

The last item that needs to be completed before uploading the new firmware is to reset your dd-wrt firmware to the default settings. A few ways to do this exist. I chose to use the standard web interface because it is easy and should always work. Nonetheless, pressing and holding the reset button on the back of your router for 30 seconds should also work (assuming you have not disabled that feature in your custom firmware).

To reset the router to firmware defaults, go to the internal IP address of your router (most likely 192.168.1.1) and login with the user name and password you setup when you first installed the router (if you have trouble with the login use the reset button method). Once logged in, go to “Administration” tab and the “Factory Defaults” sub-tab. I forgot to write down the exact buttons and also forgot to take a screenshot of this step but I think you just select the “Yes” radio button next to “Restore Factory Defaults” then select “Save Settings.” If that’s not it exactly, you shouldn’t have any trouble determining what to select. Be patient and don’t touch anything because the reset could take a couple of minutes.

The Tomato FAQ recommends that you Telnet into your router before performing the flash and type the “nvram get http_passwd” command to obtain the password that will be used by Tomato after the flash. You cannot just use the dd-wrt password because of a change in the way dd-wrt uses the standard http_passwd variable. I must admit that I did this step but the password I obtained during the Telnet session did not allow me to login. However, as I was writing this tutorial, it occurred to me that I may have obtained the password via Telnet before I reset dd-wrt to the default settings which may explain why the password I obtained did not work.

In order to Telnet into your dd-wrt router, open up the run box by hitting the “Window” key and “R”. Next type “cmd” and hit “Ok.” In the command window, type “telnet 192.168.1.1″ where 192.168.1.1 represents the IP address of your router. You will be prompted for a user name and password. The telnet user name is always root even if you login to the web interface with a different user name. The password should be the default dd-wrt password of “admin” since you just performed a reset. If not, try your old web login password.

Just so you know, Telnet is not enabled in Windows Vista by default but is in XP. To enable Telnet in Vista follow the instructions at Tech-Recipes site. Alternatively, you could use a tool like Putty.

The screenshot above shows the password command being typed into a Telnet session; it does not show the output of the command (i.e., my password).

Write down the password provided because you will need it later.

The next few steps is where the magic starts to happen. Go back to the dd-wrt web interface. You may have to renew the DHCP lease and login again. Since you have reset the firmware to default settings, the user name and password is now “root” and “admin”, respectively. Once logged in, navigate to the “Administration” tab and the “Firmware Upgrade” sub-tab.

Next, select the “Browse” button and select the “WRT54G_WRT54GL.bin” file you downloaded early. Once located, hit open (no brainer). Then hit the “Upgrade” button. Please wait patiently for the upload to complete. Whatever you do, don’t interrupt it. If you’re going to be tempted, walk away for a few minutes and come back.

After a couple of minutes, you should see a screen that says “Upgrade successful. Unit is rebooting now. Please wait a moment…”

Once the reboot completes, you will be prompted to login to the Tomato firmware. This is where you use the “root” user name and the password you obtained via Telnet. Don’t freak out if you can’t login…the same thing happened to me. The next paragraph has a solution for you.

Since the Tomato interface did not accept the password I obtained through the Telnet session before the flash, I had to perform a hard reset. To do this you need to hold the reset button on the back of the router while unplugging the router. Continue to hold the reset button as you re-plug in the router. Once the router is plugged in you should continue holding the reset button for 30 seconds to complete the hard reset.

After the hard reset is complete, go back to Firefox and navigate to http://192.168.1.1. At the prompt enter in “root” for the user name and “admin” as the password. The Tomato web interface should come up.

Once you’ve logged in, you should see the new Tomato firmware. Since you are upgrading from dd-wrt, the Tomato FAQ recommends performing a full reset by navigating to the “Administration” section and then the “Configuration” sub-section. From there, select “Erase all data in NVRAM memory (thorough)” from under the “Restore Default Configuration” menu and then hit “OK.” If you had to do a hard reset in order to get your login to work, you’re probably could skip this step but it won’t hurt to do an additional reset just to be safe.

After restoring the default configuration, you need to log back in using with the user name of “root” and password of “admin”. Once logged in, hit the “Renew” button that is on the “Overview” page.

After renewing you may need to reboot your computer to get Internet access. Alternatively, in Vista you may type “Network and Sharing Center” in the Start Search box. Within the Network and Sharing Center select the red “X” between the network on Internet on the map. The Windows Network Diagnostics menu should appear. On that menu select “Reset the network adapter…” option at the bottom. Windows will repair the network and you should see a message that says “the problem has been resolved.”

Now that everything is working, don’t forget to turn your anti-virus and firewall back on. Also, be sure to check out my Securing Your Wireless Network article if you want to learn how to have a really secure wireless network.

Congratulations, you’ve successfully flashed your router! Since you’ve successfully flashed your WRT54G, you should checkout the Linksys WRT54G Ultimate Hacking Guideto make the most out of your new found knowledge of router firmware.

Further Reading

• Tomato Firmware Option for WRT54GL
• Tomato Firmware Upgrade and Demo Video
• How to Flash the WRT54GL with DD-WRT Firmware
• Securing Your Wireless Network

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With Comcast’s new 250 GB bandwidth limit and Tomato’s impressive bandwidth monitor, I’m getting even closer to taking the time to make the switch from dd-wrt to Tomato. I believe the v24 of dd-wrt does support bandwidth monitoring but I like the looks and basic features of Tomato.

The Systm episode 71 by Revision3 recently covered the process to flash a Linksys WRT54G with Tomato firmware and also showed off some of the application’s coolest features. If you’re debating on upgrading your very basic Linksys router to something much better for free, I highly recommend you watch this video. It’ll make you want to do it right away.

Now, if I can just determine the best process to switch from dd-wrt to Tomato, I’d be good…

Also should also mention that if you’re interested in hacking your Linksys router, you should checkout the Linksys WRT54G Ultimate Hackingbook.

As far as I know, this vulnerability is unpatched by Linksys which means there is update to fix this problem if you want to keep running the standard Linksys firmware. However, you can fix this vulnerability and gain additional features by upgrading to an open source firmware such as DD-WRT or Tomato. I happen to own a Linksys WRT54GL version 1.1 and have flashed it with the DD-WRT firmware. Because flashing a router’s firmware is not for the faint of heart, I have composed very detailed how-to instructions for those who are interested.

Another mitigation method I almost forgot to mention is to actually quite simple. Do not visit other websites while logged in to administer the Linksys WRT54GL. [via Secunia]

I wish I had the time/patience to re-flash my Linksys WRT54GL with Tomato just to try it out. Its very unlikely that I will because I don’t want to risk bricking my perfectly functioning dd-wrt enabled router. I also really like dd-wrt. Too bad flashing a router is a lot more complex than just installing software.

Also, the Lifehacker article doesn’t mention OpenWRT (a couple of commenters do) but OpenWRT seems to be the hard-core geek’s choice. I’ve thought about making the switch to it but it is probably more complex than I want to deal with. I really considered OpenWRT over DD-WRT but DD-WRT’s site looked better maintained and easier to read. Plus, until recently all OpenWRT management seemed like it when through a Linux shell (i.e., command line). Now though x-wrt seems to address what some would call a short coming of OpenWRT.

If anyone wants to send me a Linksys WRT54GL so I can experiment with it and write more tutorials on firmware flashing, let me know and I can add it to my Amazon Wish List so you can send it to me easily. Also, don’t forget to check out my ever-popular “How to Flash the WRT54GL with DD-WRT Firmware” tutorial.

A lot of security topics exists that I’d love to write about sometime, but securing your wireless network is one that should be useful to most of my blog readers. Plus, this is a natural progression from my recent post about How to Flash the WRT54GL with DD-WRT Firmware. This post will not cover the intricate details of the hows and whys of wireless security nor will provide a ton of details on how to circumvent (i.e., crack) common security settings. Maybe I’ll cover those topics at a later date. For now, I just want to tell you about what security settings you should use on your home or small business wireless network to ensure no one is able to sniff (see what your doing on your wireless connection) or use your wireless connection without your permission.

Table of Contents

• Select Your Encryption Method
• Select Your Password
• Disable SSID Broadcast
• MAC Filtering
• Turn Off UPnP
• Change Default Router Log-In Settings
• Setup Your Firewall
• Patch Windows Client
• Configure Client Devices
• External Resources

Select Your Encryption Method
The first thing you must decide on is what encryption to use. The decision is pretty simple; pick the strongest form of wireless encryption that your network will support (excluding the Radius methods for reasons noted below). Remember, even if your wireless router supports the strongest encryption but some of the wireless cards joining the network does not then you will have problems connecting from those machines if you don’t pick a level of encryption supported by all of your devices. Most people with remotely up-to-date hardware will not have trouble supporting all of the encryption levels mentioned below.

Below I’ve listed the DD-WRT’s wireless encryption security mode options (these will be available in most other wireless routers) from strongest to weakest:

1. WPA2 Radius Only
2. WPA2 Radius Mixed
3. WPA Radius
4. WPA2 Pre-Shared Key Only
5. WPA2 Pre-Shared Key Mixed
6. WPA Pre-Shared Key
7. Radius
8. WEP
9. Disabled

All of the RADIUS methods are too complex for most home users because they require a separate Radius server for for authentication. RADIUS is designed for a Corporate type environment.

The DD-WRT firmware provides a second option for WPA Algorithms (for WPA security modes) or Encryption (for WEP security modes).

The WPA preferred order is:

1. AES
2. AES + TKIP
3. TKIP

The DD-WRT help file suggests using WPA2 Mixed/TKIP+AES for maximum interoperability. So if you’re having trouble getting WPA2 AES to work on your network, try this configuration. Also note that WPA2 TKIP is not supported. Don’t worry, any form of WPA is very secure.

For WEP, the preferred order is:

1. 128-bits 26 hex digits
2. 64-bits 10 hex digits

Below is a screenshot of the encryption settings I recommend:

Note: Both forms of WEP are easy to hack due to poor implementation of the RC4 Stream Cipher; don’t worry what this means right now, just know its really insecure. Also, note some people call 128 bit 105 bit WEP and 64 bit WEP 40 bit because they subtract the 24 initialization vector (IV).

Select Your Password
Password selection is of vital importance as well because if someone can easily brute force your password (quickly determine your password by trying all possible values) then the strongest form of encryption is worthless. Some people claim WPA has been broken, but in reality all that has really happened is someone sniffed a lot of packets and then carried out a dictionary or brute force attack and correctly guessed the password. A WEP password doesn’t really matter as a WPA password because a hacker with a little time and some free tools can quickly determine your WEP password due to the improper implementation of the encryption algorithm.

So, how can you make it practically impossible to brute force your password? The answer is simple…use a long, random password. The longer the password the more time brute forcing takes to work (as in thousands of years for a strong password). Basically, brute forcing tries all possible combinations of letters and number (or a predetermined sub-set of them) until the combination works so the longer the password the more guesses required. Randomness protects against dictionary attacks. A dictionary attack is just like it sounds. A very large list of common passwords is tried; therefore, you don’t want to use any words that may be in a dictionary.

Because you are not required to enter your wireless password more than once on each client you want to connect to your wireless network, you can easily select a very long and complex password and not worry about having to memorizing it. GRC has an excellent random password generator perfect for wireless security. Use the 63 random printable ASCII character for ultimate security. Why 63 characters? Its the maximum length accepted by WPA.

Although I trust GRC’s Ultra High Security Password Generator, I still hit the refresh button a few times to collect a small selection of passwords. Then, I cut and pasted tidbits of each password to ensure its security–I know you think I’m crazy.

Of course, you must store this password in a protected place to keep others from finding it. I recommend putting it on a portable storage device such as a CD or USB drive. If you want to be ultra secure, and geeky, store the password in an encrypted form with a tool such as TrueCrypt.

WEP requires you to use an exact password length so you won’t be able to use the full 63 character long password generated by GRC’s Ultra High Security Password Generator. 26 hexadecimal characters equates to 13 alpha-numeric characters and 10 hexadecimal characters equals 5 alpha-numeric characters. If you must use WEP, you can just select the appropriate subset (26 characters for 128bit WEP and 10 characters from the 64bit WEP) from the 64 random hexadecimal characters section of the password generator.

Disable SSID Broadcast
Hiding Your Service Set IDentifier (SSID) doesn’t provide much security because anyone using a tool such as Kismet can still find your SSID, but at least your wireless network ID will be hidden from the average Joe. If you do hide your SSID, your network will not show up when you scan for wireless networks in Windows or OS X so you must manually type in the SSID name you selected on each client when you first time connect to your network.

MAC Filtering
MAC Filtering is a way to limit what network cards can connect to your network. Every networking device has a unique MAC address assigned to it during the manufacturing process. To set up MAC filtering, you will need to determine the MAC address of every device you want to connect to your network and enter this information into the router.

As you can tell, I have MAC Filtering disabled. Why? Its takes quite a bit of time to setup and it doesn’t provide much security. The idea behind MAC filtering is good, but its flawed because a user is able to change their MAC address to anything they want. So, a someone wanting to access your network would use a good wireless sniffer (i.e., Kismet) to determine what MAC addresses are connected to your network. They would then change their MAC address to one of those allowed addresses. Because MAC addresses are supposed to be unique, your access point will get confused if two clients with the same MAC address is connected to it. So, a smart hacker will kickoff the original machine whose MAC address they stole using a common Denial-of-service (DOS) attack or simply wait for that machine to disconnect.

You must decide whether or not MAC Filtering is worth the trouble because it does provide some protection.

Turn Off UPnP
Another worthwhile security measure is turning of Universal Plug and Play (UPnP) on both your PC and your router. UPnP is bad because it lets software automatically open ports on your router without your knowledge. To make it even worse, you can’t tell which ports have been opened. The idea behind UPnP was to make it easy for network software/devices to work without a user having to manually configure Port Forwarding.

The problem is that malware could also use this auto-configuration feature to open ports behind your back in order to communicate with the outside world. Additionally, UPnP has several major vulnerabilities in the past such as buffer overruns that could lead to remote code execution. Although the known vulnerabilities have been patched, turning off UPnP would prevent any future exploits.

The easiest way I know of to turn off UPnP on your PC is to use the UnPlug n’ Pray utility.

Go to the Applications and Gaming tab and the UPnP sub-tab to disable UPnP.

Note: I believe most routers not running the DD-WRT firmware have a similar option to disable UPnP. If not, disabling it on your PC should be enough as long as Windows, as it has bad habits of doing, doesn’t decide to turn the feature back on.

It is important to reset your router to factory defaults to undo any ports opened by UPnP when it was enabled. Please note that resetting your router to factory defaults will also reset any of your custom options, so think twice before doing this. Be sure to reset your router before completing the rest of the security steps or else you’ll probably have to re-do them. See the following two pages on the DD-WRT wiki for information on how to perform a reset: Factory Defaults & Reset and Reboot.

I am uncertain, but simply rebooting (not resetting) your router may also undo the ports opened by UPnP. One way to ensure all your important ports have been closed is to check out the Shields Up web service. If you want to do a full port scan check out NMAP.

Change Default Router Log-In Settings
Changing the User Name and Password used to configure your router is very important (this is the info you type in when going to 192.168.1.1 o whatever your router’s internal IP address is). The default router user names and passwords are widely known…you can easily find a massive list of them. Symantec published an article on a very interesting concept they coined “Drive-By Pharming: How Clicking on a Link Can Cost You Dearly.” The basic concept is Cross Site Request Forgery can be used to log in to your wireless router if you haven’t changed the default log-in settings. Once access has been gained to your router, your DNS Server setting can be changed to a malicious DNS server. This is a major problem because DNS associates domain names (web site addresses) with server’s IP addresses. A malicious DNS server could associate your-bank.com with spoofed site that looks just like your bank’s site and collect your user name and password when you try to log in. However, the simple change of your router’s user name and password protects against this attack.

Go to the Administration tab and the Management sub-tab to change the default settings. While your there, go ahead and disable all Remote Access as well.

Setup Your Firewall
Firewalls are set rules for what can come in and out of your network. One of the main benefits of all routers is Network Address Translation (NAT). Basically, it only allows connections into your network if one of your computers made the initial request. Sometimes you will need to use Port Forwarding to allow connections through certain ports for services running behind your router that you won’t make the initial request…for instance you’re running a web server on your network that needs to accept connections on port 80. If you recall, UPnP automatically configures port forwarding which could open up ports you don’t want open.

Stateful packet inspection (SPI) provides an extra layer of security to NAT routers. I recommend enabling SPI, blocking anonymous Internet request, filtering multicast, and filtering IDENT. You can set all of these by going to the Security tab and the Firewall sub-tab.

Patch Windows Client
One thing I do recommend is downloading the following patchs from Microsoft: The Wi-Fi Protected Access 2 (WPA2)/Wireless Provisioning Services Information Element (WPS IE) and Wireless Client Update for Windows XP with Service Pack 2.

The first update “enhances the Windows XP wireless client software with support for the new Wi-Fi Alliance certification for wireless security. The update also makes it easier to connect to secure public spaces that are equipped with wireless Internet access.”

The second update “enhances support for Wi-Fi Protected Access 2 (WPA2) options in Wireless Group Policy. This update helps prevent a Windows wireless client from advertising the wireless networks in its preferred networks list.” Please note that this patch was never included in any automatic updates from Microsoft. Unless you specifically went to Microsoft to download this patch, your system will not have it (as far as I know anyway). Don’t ask me why Microsoft didn’t include this in their standard update cycle.

Configure Client Devices
You should configure Windows to only connect to Access Points because Ad-Hoc (computer-to-computer) networks are dangerous. To do this go to Start > Control Panel > Network and Internet Connections >Network Connections then right-click on Wireless Network Connection device and select properties. On the Wireless Network Connections properties screen select the Wireless Networks tab and then the Advanced button. Make sure to select Access point (infrastructure) networks only and uncheck Automatically connect to non-preferred networks.

You will also need to add your network to the preferred networks list by going back to the Wireless Networks tab and selecting Add. Then type in the appropriate information for you wireless setup.

External Resources
To learn more about Wi-Fi security, I recommend listening to the following episodes of Security Now:

• Episode 10: Open Wireless Access Points
• Episode 11: Bad WiFi Security (WEP and MAC address filtering)
• Episode 13: Unbreakable WiFi Security
• Episode 14: Virtual Private Networks (VPN): Theory
• Episode 15: VPN Secure Tunneling Solutions

Note: Each Security Now podcast also have text transcripts.

I also recommend checking out the following articles:

• Wireless Security
• Wireless LAN Security
• Hacking Techniques in Wireless Networks

I realize this is a long, fairly technical post so feel free to ask any questions, correct any mistakes, offer suggestions, or anything else using the commenting feature below. If nothing else, just let me know if you found this post useful. Thanks!

Note: Although I touched on a few ways to get around wireless security, I do not advocate doing so. I mentioned some of the techniques because the best way to secure against attacks is to know what attacks are out there.

This tutorial explains how I successfully flashed my Linksys WRT54GL version 1.1 with the open source dd-wrt version 23 SP2 VPN firmware (generic). If you happen to have Linksys WRT54GL version 1 rather than 1.1 (you can tell by the serial number prefix of CL7A for version 1.0 and CL7B for version 1.1 per the Wikipedia entry and dd-wrt Wiki), you may have to follow slightly different instructions. The main difference is that you will need to flash to a smaller version of the dd-wrt firmware (the mini version) first due to a flash file size limit on the version 1.0 WRT54GL firmware before flashing to the standard, VOIP, or VPN versions.

As a bit of background information, I’m used a fully patched (as of April 6, 2007) Windows XP Pro with Service Pack 2 (SP2) and Internet Explorer 6 during the firmware upgrade process. The OS and web browser shouldn’t matter that much, but I have heard reports of Firefox causing some problems with the Flash for some people in the past though others have claimed to use Firefox without any problems–just a word of caution.

Before you begin, download the package and version of the dd-wrt firmware best suited to your needs though this tutorial walks through flashing to the open source dd-wrt version 23 SP2 VPN firmware. Once you’ve downloaded the file, go ahead an unzip the files. The zip package contains several files, you will only need the “dd-wrt.v23_vpn_generic” file. We’re going to be using the generic file rather than the wrt54g file because we’re going to be using the web GUI to upload the file.

I recommend verifying the MD5SUM hash of the “dd-wrt.v23_vpn_generic” file to ensure the download wasn’t corrupt or hasn’t been comprised. If you don’t already have a tool to calculate MD5SUMs, I recommend using HashCalc although you must manually compare the sums with this tool unlike another tool I can’t seem to think of right now. The signature of the file should be baf91850d3204fd64b120467425b4a11. If you plan on flashing a different version, you can find of list of signatures on the dd-wrt hashes page.

While your at the dd-wrt website, I recommend printing (or at least saving, not bookmarking, to your hard drive) the following pages for reference since you will not have Internet access during this process:

• How to Flash the WRT54GL with DD-WRT Firmware
• Installation
• WRT54GL Specific Instructions
• Reset and Reboot
• Recover from a Bad Flash

It is best to turn off your firewall and anti-virus during this process to ensure that nothing interrupts the firmware flash. An interruption could cause the flash to fail and brick your router. If something does go wrong you may be able to recover from a bad flash.

Almost forgot to mention, you should ONLY perform the flash through an Ethernet cable using standard http (not https). Do not do this wirelessly (its best to temporarily disable the wireless adapter on your computer). Plug the blue Ethernet (Cat5/RJ45) cable that came with your router into the Network Interface Card (NIC) on the back of your computer and into one of the ports labeled 1, 2, 3, or 4. The “Internet” port on your router should be connected to your broadband source (e.g., cable or DSL modem). Please ignore the extra cable in the picture. It is not needed for the flash to work.

The last item that needs to be completed before uploading the new firmware is to reset your Linksys router to the factory defaults. A few ways to do this exist. I chose to use the standard web interface, but the pressing and holding the reset button on the back of your router for 30 seconds should work just as well (assuming you’re using the factory Linksys firmware, if not be careful). To reset the router to firmware defaults, go to the internal IP address of your router (most likely 192.168.1.1) and login with the user name and password you setup when you first installed the router (if you don’t know those use the reset button method). Once logged in, go to “Administration” tab and the “Factory Defaults” sub-tab. Select the “Yes” radio button next to “Restore Factory Defaults” then select “Save Settings”.

If the reset was successful, you will say a page that says “Settings are successful. You will be returned to the previous page after several seconds.”

Now that everything is setup we can begin the process of actually performing the flash. To upload the firmware, navigate to the “Firmware Upgrade” sub-tab under the “Administration” tab. On this page, select “Browse” to go to the place where you saved the “dd-wrt.v23_vpn_generic” file. Once located, hit open (no brainer). Then hit the “Upgrade” button. Please wait patiently for the upload to complete. Whatever you do, don’t interrupt it. If you’re going to be tempted walk away for a few minutes and come back.

If all goes well, you will great a screen that says “Upgrade is successful”. On that screen hit the “continue” button to, you guessed it, continue. If not successful, simply re-try the same steps or research the dd-wrt wiki for more info.

The next thing you should see is a prompt to login to the new dd-wrt interface. The default user name is “root” and the default password is “admin”. Be warned, I wasn’t able to log-in initially even though I got this prompt.

To confirm that your router is working you should ping it. To ping your router, go to “Start > Run” in windows. Then type in “cmd” and hit “ok”. At the command prompt type in “ping 192.168.1.1″. If the router is online, you will get a ping response that says Packets Sent = 4, Received = 4, Lost = 0 (0% lost).”

Since the dd-wrt web interface didn’t come up right after the flash, I rebooted my computer (the common solution to lots of Windows problems). That didn’t work even though rebooting probably isn’t a terrible idea. What did work was resetting the new dd-wrt firmware back to firmware defaults. To do this you need to hold the reset button on the back of the router while unplugging the router. Continue to hold the reset button as you re-plug in the router. Once the router is plugged in you should continue holding the reset button for 30 seconds to complete the hard reset. I had to do this a couple of times because I didn’t reset it correctly on the first try.

Once reset, go back to Internet Explorer and navigate to 192.168.1.1. At the prompt enter in “root” for the user name and “admin” as the password. Mysteriously, the dd-wrt web interface should come up.

Congratulations, you’ve successfully flashed your router! Since you’ve successfully flashed your WRT54G, you should checkout the Linksys WRT54G Ultimate Hacking guide to make the most out of your new found knowledge of router firmware.

Now that your running DD-WRT firmware, make sure to make use of all the available security features. See my post on Securing Your Wireless Connection and other post in the dd-wrt category.

If you liked this post, consider subscribing to my feed and/or sending me something from my wish list. One other option is to send me a Linksys WRT54GL so I can do some more experiments and write more tutorials. Thanks in advance for your support of this guide & site!!!