From DD-WRT Wiki
Initial flash of DD-WRT firmware is done though Netgear update GUI using a device specific .chk file
If the firmware you are loading is before svn11600 then you will need to update the firmware using dd-wrt.v24-11604_WGR614v8-L_mini.bin first before upgrading to a newer build. After the initial .chk flash (after svn11600) any generic .bin file can be used to upgrade firmware to the router using the DD-WRT Firmware update tab.
These are the notes provided by Eko.
Files listed are located here.
 Flashing Netgear WGR614v8/L/WW
- For first flash (running original Netgear's firmware) or for TFTP please use dd-wrt.v24_mini-wgr614v8-L file. Browse the database or download the build 14929 here.
- For upgrade when already running DD-WRT (IMPORTANT!):
- if your DD-WRT build is less then 11600 please use dd-wrt.v24-11604_WGR614v8-L_mini.bin file. Then you can upgrade to any build listed below.
- if your DD-WRT build number is greater then 11600, you can upgrade directly using any build listed below. Keep in mind that as newer builds come out (higher svn numbers than 11600) they are also compatible.
Builds that must be compatible:
dd-wrt.v24_std_generic.bin- Causes an "Upgrade failed" message.
- dd-wrt.v24_nokaid_generic.bin - Recommended
Additional wiki information about the WGR614v8 can be found here. Some of this data is outdated but it could still provide to be useful.
Also note that any builds after 16235, nokaid has become to large to fit, you will then have to use mini only
 Simplified Installation Notes
Installation on a brand new WGR614L running stock firmware goes like this:
- Set a static IP such as 192.168.1.8 with a subnet of 255.255.255.0 and gateway 192.168.1.1 on the PC you will be using for the flash. Preferably a WinXP machine.
- Connect the PC to the router (unplug everything else except the ethernet cable and power supply on the router)
- Perform a 30-30-30 Hard Reset on the router.
- In Internet Explorer, go to http://192.168.1.1 . Default login : admin / password .
- Cancel the router’s automatic firmware update checking, then click on “Router Upgrade” in the menu at left.
- Upload the special *.chk firmware file which can be downloaded here.
- Wait 4 minutes, then after waiting 4 mins and the router says it is done, then perform another 30-30-30 reset.
- Now, try to connect to http://192.168.1.1 . You must discover the DD-WRT Web GUI :-) Your router is running the mini build (see the comparison). If you want more features, you have to upgrade to another version. Go to the next step.
- Click on the "Administration" tab and select "Firmware Upgrade" page.
- Browse to the new firmware file (*.bin). Recommended as of June 2011 is build 14929. You can download it from the ftp.
- Select "Reset to Default settings" and click on "Upgrade".
- Wait 2-3 minutes. You can now login again and start setup !
The WGR614L uses NEWD builds, use any Newd-2 or K26 Newd-2 at your own risk The max flavor you can put on the WGR614Lv8 is Nokaid. The Peacock-Broadcom Faq explains why.
 VLANs Support
The WGR614v8/L supports VLANs
Use the Switched Ports Guide as a reference on how to do it from the shell, I have not tested it from the webgui, most likely it will work fine with it. -buddee