Most network routers have fairly basic firmware that limits the hardware's full potential. You can change that.
I know this first hand, as I picked up an ASUS RT-N12 router from a good friend of mine recently to replace my underwhelming Belkin branded one. Although ASUS hardware is mostly of high quality, the firmware felt rather raw and unpolished. With that in mind, I did some research online and found that custom router firmware was available and I decided to give it a try.
Eventually, I settled on DD-WRT, which is quite honestly one of the best router firmware packages I've ever used. For those who are unfamiliar with it, DD-WRT can be flashed on any compatible router in order to grant the user extra functionality, which hardware manufacturers seem reluctant to include in stock software. Once you flash your router, you probably won't want to go back. You quite literally get everything but the kitchen sink at your fingertips.
DD-WRT is filled with numerous tweaks and options
For an idea of what DD-WRT can do for you, I will highlight some of my favorite features included with the firmware.
If you wanted to set up an OpenVPN gateway for all systems that connect through the router, you can add your VPN cert and private key, flip a few switches to determine the encryption and tunnel type, and voila! Every computer that connects to the router will pass right into the VPN. No client end VPN software is necessary.
I also like how DD-WRT is extremely verbose on stats, showing you total inbound and outbound traffic to date, as well as router performance information, including free memory and CPU activity. Having access to this panel will give you insights into what kind of traffic you are dealing with and if you need additional hardware down the road.
An example of some of the available router stats
Finally, DD-WRT just seems to improve network performance by a decent margin. For instance, after switching the firmware from stock to custom, surfing web pages and downloads seemed a bit snappier than before. Not to mention, I could be more discriminatory of what protocols (i.e. Bittorrent) could do what it needed to do with the network to improve balance.
Installing takes some research
Now, when it comes to getting DD-WRT installed to the router, there really is no one-size-fits-all method, as hardware from different manufacturers is handled on a case by case basis. There are some routers that are unable to be flashed too, so if you are shopping around for a new router, it would be advisable to refer to the DD-WRT hardware compatibility database first before committing to a purchase.
Fortunately, for my router, installation was as simple as dropping into the firmware upgrade menu, selecting the custom-tailored ROM file for my hardware make and model, and then uploading it over the network. After a several minute upload process, followed by a mandatory router reboot, I was up and running in DD-WRT. In the unfortunate event of an endless reboot or other strange issue that might arise in the process of flashing, I also have the option to boot into the router's low-level recovery mode in order to roll back to the stock firmware and try again.
With all this interest surrounding router modifications, it goes without saying that flashing with un-official custom firmware could invalidate your warranty coverage and cause other problems. If this all sounds too risky, companies like Buffalo actually offer routers with DD-WRT firmware already flashed and ready to go with full warranty coverage. This way, you won't have to worry about accidentally bricking any hardware if you don't feel adventurous.
DD-WRT is available to everyone as freeware under the GNU GPLv2 license. So long as your router make, model, and revision are all listed, you should be good to go. One thing to note: if you have less than 8MB of flash storage space on your router, you won't be able to take advantage of every feature available. Therefore, you will need to choose the mini firmware "edition" that best suits your needs for the hardware.