Recovering from a bad flash
Occasionally, a flashing attempt goes bad, leaving the router "bricked" -- it seems to be starting up, but otherwise doesn't provide network access and the management pages are unreachable. Another common symptom: The power light on the front panel of the router flashes nonstop.
Fortunately, a flash problem is rare, and there are ways to recover from it. The first thing to do is try a hard reset, or a "30/30/30" as the DD-WRT folks call it:
- Unplug the router from the network (but not the power) and hold the hardware reset button for 30 seconds.
- Keep the reset button held down and remove the power cord for 30 seconds.
- Plug the power back in and keep holding reset for 30 seconds.
- Let go of the reset button and unplug the power one last time for a minute or so. Restore power.
This resets the router to its factory default state, which is sometimes needed to get it to boot properly after a flash. If that doesn't work, then you'll need to look into one of the more advanced recovery procedures listed on the DD-WRT wiki. These include recovering via TFTP (as mentioned above) or using a JTAG cable -- a physical cable connected directly to the router -- for repair. If that sounds hairy, it is. JTAG involves hardware hacking, so is probably best suited for the hardcore and those who have absolutely no other choice. A truly wizardly DD-WRT hacker may also add his own boot logic (such as Micro Redboot), especially if he plans on trying out a variety of different firmwares.
DD-WRT features and functions
Once you have your DD-WRT router booted up and configured, log into the router's administration page (be sure to change the default password!) and find out which features your router supports. A full breakdown of all the features in DD-WRT would require a book and might well be redundant since many of the features are common to most routers. However, here's a sampling of features included with DD-WRT but that might not be present on other routers you've worked with. (Note that not all routers support these options.)
- AOSS. Short for AirStation One-Touch Secure System, AOSS is supported in some clients and routers (they'll have some statement to the effect in their documentation). If your router supports it, you'll be able to press a button on the face of the device to allow an AOSS-enabled client to connect without the need for a password. Many portable game consoles, like Sony's PSP, use AOSS.
- Boot wait. When enabled, the router pauses for five seconds at boot time to allow the user to connect remotely and flash a new firmware if the current one is bricked. Leave this on, as you never know when it'll be useful -- and what's five measly seconds out of a reboot cycle?
- Logging. DD-WRT can maintain running logs of its most crucial events and behaviors. The log can either be kept locally or be written to a remote IP address that has a syslog daemon listening on the appropriate port. This can be left off by default, but it's useful to toggle it on if you need to do any detailed troubleshooting (for instance, to find out if some specific action is messing things up).
- NTP client. With this, you can specify a remote timeserver that the router will use to synchronize its own clock. This is a good idea generally, since it saves you the trouble of having to set the clock by hand, and it allows for more accurate deployment of scheduled reboots (see below).
- Overclocking. Some routers support the ability to overclock, or they run the CPU faster than the manufacturer normally recommends. There are few cases where this is needed, especially since overclocking any hardware often leads to instability.
- Scheduled reboot. You can force the router to reset itself at a given time of day, after a certain interval, or on a specific day of the week. Some claim this improves performance, although in my own experience it doesn't seem to make much difference. The documentation (linked above) shows you how to do this via a command line, but some builds -- including the one in my Buffalo router -- let you set this in the GUI under Administration/Keep Alive. Note that in order to use this, you'll need to enable the Cron option as well.
- Telnet. The telnet daemon should be running if you plan on connecting via telnet to perform administration (such as to manually flash new firmware). If you're worried about the security implications of leaving telnet running, you can shut it off until you need it.
- Trasmit power and antenna gain. These let you control the power to the wireless antenna and the amount of gain or "focus" used to single out weaker signals. Most of the time these options should be left as-is -- especially if they're already specified by your router's manufacturer in its DD-WRT stock firmware -- but you can experiment with the gain function to see if it improves reception in your environment. Note that raising transmit power can cause some routers to overheat, so don't fool with it and then forget about it.
- Watchdog. If enabled, the router will attempt to ping other computers regularly and will reboot itself if it doesn't receive a response. This should not normally be needed, but it can be useful if you have a flaky network gateway. Just be sure to use sane intervals for the pings -- anything less than five minutes is probably overkill -- and make sure you're pinging something whose inaccessibility will be a sure sign of trouble (Google, for instance, or your ISP's home page).