Updating d link firmware
The "variable" changes whenever DNSMasq sees a conflict.The lease table is cleared when the router is upgraded, unplugged, rebooted, and in situations where a config change requires a reboot.After a power cycle suddenly your setup is gone and the router restarts in its default and unsafe state.
For cable and satellite users, generally DHCP is the correct setting. For users trying to share a dial-up connection, you'll need to read the Wiki article Sharing Dialup.
At any rate, it's a near 99% chance that the problem is not your DD-WRT firmware, but instead a lack of understanding with networking. DD-WRT uses DNSMasq and does not give sequentially ordered IP addresses.
Since this question involves many variables, we do not have an article for it yet. If the power light flashes on and off, then the firmware is messed up, but the router should be recoverable. It may also be possible that your router has a different IP address.
The CPU must be running in order for the power light to be flashing, which tells you the hardware is probably not toasted yet. If you do not know the address, you can attempt to obtain the router IP. If you're able to get a reply for a short time, you should be able to reflash the firmware while the router is booting.
You can also buy a router with DD-WRT preinstalled if you want to avoid the hassle of installing DD-WRT, although this is often more expensive. First of all, DO NOT USE THE ROUTER DATABASE, it is old and outdated. #File Versions to know which image has which feature-set.
Note 1: All builds on the ftp are released without being tested, or minimally (only some hardware). Note 2: You may want to read the relevant build thread on the forum.
A standard build is required to use Open VPN, which requires at least 8mb flash.
Here are some other good choices, as of Nov 2017: One can also search on Amazon for DD-WRT compatible routers just make sure to double check them against the Supported Devices list.
If your computer's IP address is 192.168.0.50, you may not be able to access the interface.
DD-WRT firmware default settings (sometimes called factory defaults) are stored in NVRAM. Flashing with TFTP must not be seen as the standard procedure for flashing: only use it when specifically told to do so (for example in the specific instructions for flashing your brand or type of device).
Normally, the GUI flashing method should be used; this should be adequate for standard situations. If you forgot your username or password, see Hard reset or 30/30/30 and Reset And Reboot.