@Shaamaan a quick update. After reenabling ARP binding it works.  Weird. I'll keep you updated if it stops working again.

@PunchEnergy 

I honestly don't think it works, not really, anyway. What app are you using to send the magic packet? I'm willing to bet that the app's sending a regular broadcast packet, which is why WOL works from LAN.

EDIT: And, yeah, re-enabling the binding will keep it working from WAN until the C6 forgets the binding again or the router reboots (due to a temporary power failure or something).

@Shaamaan I have reenabled ARP-Binding and pulled the plug afterwards. Then let the router reload and it worked just fine. Of course the pc was off all the time - I even cut off the power to the PC aswell.

I am using this app: https://play.google.com/store/apps/details?id=com.gianbresa.wake

These are the in-App-Settings i am running with:

@Shaamaan, I´ve been having the same problem since I got my Archer C6 two weeks ago, and it was driving me crazy. I could wake my computer from my Android phone at any moment, no matter how long it had been shut down, as long as I was in the same LAN (using my local IP), but it would only work for a couple of minutes after shutting down if I were outside (using no-ip DDNS). That led me to the conclusion that everything was set up correctly on the computer.

Reading your posts, I noticed that my ARP table was also acting weird, with that "to be added address already exists" message (I don't remember the exact words, but you know what I'm talking about) popping up every time I tried to create a new entry. I hadn't payed much attention to that before, as clicking on the little chain link seemed to reserve the address. What you described made me realize there was some kind of conflict between the ARP table and the DHCP reservation.

So, this is what seems to have worked for me (I've been testing for two days now):

1 - I turned off my computer and accessed the router's configurations from a notebook (so the IP would not be in use).

2 - I removed the DHCP reservation for my computer, which then allowed me to...

3 - successfully create an ARP entry with my computer's MAC and IP and...

4 - I created a virtual server forwarding port 9 to my computer's IP.

That's it. It worked, without the DHCP reservation. I don't really know the difference between DHCP and ARP reservations, but they seem to conflict in this router, and the ARP alone is doing the job.

I hope this helps you. I was about to lose my mind.

@Geeohgo The conflict with DHCP isn't new - I've already noticed this and find it odd that the ARP binding option isn't already built into the DHCP setting because why WOULDN'T you want them working in tandem? Anyway, just being able to set this isn't an issue for me - with no DHCP setting to speak of I was able to add an ARP binding no problem. The issue, however, stems from the fact that it seems the C6 forgets the ARP binding after a while or a reboot, which completely breaks the desired functionality. I can re-test, of course - perhaps TP-Link finally released a new FW that addresses the problem? I can see there's a new version that was published this month that I haven't checked yet...

@Geeohgo 

Nope. Just tried the latest FW, still the same issue. I disabled DHCP and added an ARP binding manually. Status - bound. At this point WOL from WAN (using virtual server port 9 forwarding) works. Rebooted router to simulate a potential power outage. WOL no longer works, the ARP entry (while present and turned on in the settings) is no longer bound.

@Shaamaan , yes, you are absolutely right. It worked for me for about two days, until the router was restarted, then the ARP binding stopped working (so did WoL from outside of LAN).

I just ran a different test, which does not solve the problem, but corroborates the ideia that the router simply stops using ARP binding after a while:

I did exactly what I described before, and everything seemed fine. Then I restarted the router, and I could no longer wake the computer from outside the LAN. Then, from another computer (the one I want to wake was left "asleep"), I opened the router's configs, removed the previosly created ARP binding and recreated it, with the exact same settings. Then everything worked again and I was able to wake the computer from the internet, until the router gets restarted again.

So the router is probably not automatically looking at the ARP binding table when it's restarted. It's only effective after the entry is created. That's terrible. I really need WoL functionality, which, by the way, worked flawlessly for years on my previous TP-Link router.

I really hope it will be fixed in the next firmware release, otherwise I have no use for the C6.

@Geeohgo 

If you need a workaround, then you can skip the WOL from WAN, and simply enable OpenVPN on the router, and connect from your phone to your LAN using that (assuing you're not at home, of course). This might also be a valid workaround for the "router reboot" scenario, where you use WOL from WAN normally (as long as the ARP binding permits) and use OpenVPN as a fallback.

Of course, emphasis on "workaround". This is NOT the way the router should work.

@Shaamaan, that is actually a very good ideia (as a workaround) that should be very simple to implement. Unfortunately, I can't get it to work either.

I enabled the OpenVPN server in the router and configured it in my Android phone (which is where the Magic Packet sending app is). When I connect to it (from outside my LAN, obviously), everything else seems to work perfectly. I can access the router's configurations at 192.168.1.1, I can access my home security DVR using it's local IP (192.168.1.23), and whatismyip.com gives me my home's external IP but...

But WoL using my computer's local IP and MAC does nothing. It still works, even after a router reboot or many ours after the computer has been shut down, if I am, in fact, in the LAN, but I get nothing if connecting throught the VPN.

Weird, isn't it?

The only thing that works, which is waaaay less than ideal: I connect my phone to my LAN using the VPN, then I access the router's configurations (192.168.1.1), then I go to the IP and MAC binding (ARP binding) settings page, click the little light bulb to temporarily disable my computer's binding (a little red blocked symbols appears on top of it), then I click on it again to reenable it. Now I can disconnect from the VPN and use the WoL from WAN, which will work within the next couple of minutes.

So, yeah, I can get it to work, but it sucks that I have to jump through all those and hoops every time I need to remotely wake my computer.

I wonder if that is a firmware problem or if I got a defective unit. I feel almost compelled to install OpenWRT, which is frowned upon by TP-Link support (understandably), but is starting to seem like the only possible solution here.

@Geeohgo

Oh, right. Sorry. Forgot - after a reboot the router will lose ARP table information, and you're NOT on the same subnet after connecting using OpenVPN, so the router still needs to, well, route. And with no ARP entry it doesn't know how.

So, correction on the workaround: should the router reboot, you can OpenVPN to your LAN, then open the router web interface and re-enable the ARP binding (just toggling the lightbulb icon should suffice). Then WOL should work.

Again, I realize this is a terrible workaround and TP-Link should really fix this securitu bug. And it IS a security bug - while we might be interested in using the ARP bindings for WOL, it's primarily a security feature... one that stops working once the router is restarted.

Alternatively, it's possible your WOL app is only set up to use the specific computer address? In this case, set up another WOL signal to use the broadcast address (i.e. 192.168.0.255 if you're using 192.168.0.0/24...