Dedicated server issue

[dev02ify]

I've had a dedicated server that worked for 3 months but suddenly stopped working. It happened while it was running. Based on ULX logs, it looks like it was last working 9/18/13 at 1:16 AM (The last player on left at that time.)

The issue is that it only works as a LAN; the ip displays as the external ip for others, on port 27016. No one can connect to it. I can only connect to it by typing the internal IP, which for me displays as the internal IP in the game info.

Some background:

-The port has always been 27016; for some reason, 27015 wouldn't work when setting it up.
-It's on another computer on my local network
-Hosting it on this computer and the other one worked fine for both.
-I was able to connect from this one to the other, or this one to this one.
-Connecting from this one to the other one worked, but [I]randomly[/I], when I spawned props on the server, everyone's ping except mine would shoot up to 996 and they would get horrible lag. A restart fixed it when it happened. I connected using the external IP.
-The two computers are connected to a [url="http://www.gadgetreview.com/wp-content/uploads/2012/08/NETGEAR-XEB1004-100NAS-4-port-Powerline-85-Mbps-Adapter-Kit.png"]powerline switch[/url] which is connected to the router
-The service is at&t U-verse
-DHCP is on, but IP addresses never change.

The issue now:

-I'm unaware of any changes that may have happened to the router. Forwarding for other game servers still works fine.
-There was no change done to the computer when it stopped working.
-It doesn't work when hosted from this computer either.
-It's a LAN now; when connecting to it, the internal ip shows in the console instead of the external like normal.
-I've tried with a completely clean installation of garry's mod.
-I had the minimum number of ports needed open originally; shooting it up to 27005-27050 for TCP and UDP still doesn't help.
-Changing back to 27015 doesn't help.
-I've tried removing the workshop installation command from the server script.
-Other game servers hosted on both computers work fine.
-Other people typing connect [external ip]:port doesn't work.
-I've tried sv_lan 0
-I've tried updating the garrysmod server installation
-There aren't any other devices on the network forwarded with the same ports.

Server console at startup:

Console initialized.
ConVarRef mat_dxlevel doesn't point to an existing ConVar
Game.dll loaded for "Garry's Mod"
Initializing Steam libraries for secure Internet server
Steam_: BugslayerUtil.DLL not found
Logging into anonymous gameserver account.
Fetching Workshop Addons.. No -authkey
Network: IP 192.168.1.71, mode MP, dedicated Yes, ports 27016 SV / 27005 CL
Error loading cfg/trusted_keys_base.txt
Error loading cfg/pure_server_minimal.txt
PREP OK
Lua JIT is DISABLED!
Executing dedicated server config file server.cfg
Map cycle file 'cfg/mapcycle.txt' was not found
Nav File is wrong or something (1)
Initializing Steam libraries for secure Internet server
Logging into anonymous gameserver account.
Connection to Steam servers successful.
   Public IP is [external IP here].
Assigned anonymous gameserver Steam ID [Too lazy to type this].
VAC secure mode is activated.

Startup script:

cd C:\srcds\games\
srcds.exe -console -game garrysmod +gamemode spacebuild +map gm_new_worlds -maxplayers 16 -port 27016

I'm not looking for criticism on my setup and extreme ignorance about computer networking. I'm looking for a solution to the immediate problem.

Thanks

[Svenskunganka]

[B]DHCP[/B] opens all ports to a specific LAN machine, so you should disable that and just forward the ports you need.

I've stumbled upon a few fellas that have issues with AT&T and it seems to me that AT&T has blocked port 27015. This might not be your issue but it's worth a shot; append your port range to 27215 instead of 27016 and add 27215 to the cmd params.

[dev02ify]

[QUOTE=Svenskunganka;42430360][B]DHCP[/B] opens all ports to a specific LAN machine, so you should disable that and just forward the ports you need.
[/QUOTE]

Not really sure what you mean here. I didn't think that's what DHCP does... I see "DMZplus" in the configuration for each device (which is of course not enabled for any devices.) Is that what you meant?:
[QUOTE="Device configuration"]Allow all applications (DMZplus mode) - Set the selected computer in DMZplus mode. All inbound traffic, except traffic which has been specifically assigned to another computer using the "Allow individual applications" feature, will automatically be directed to this computer. The DMZplus-enabled computer is less secure because all unassigned firewall ports are opened for that computer.

Note: On LAN devices which have a Private IP address, once DMZplus mode is selected and you click save, the system will issue a new IP address to the selected computer. The computer must be set to DHCP mode to receive the new IP address from the system, and you must reboot the computer. If you are changing DMZplus mode from one computer to another computer, you must reboot both computers.
[/QUOTE]

[QUOTE=Svenskunganka;42430360]I've stumbled upon a few fellas that have issues with AT&T and it seems to me that AT&T has blocked port 27015. This might not be your issue but it's worth a shot; append your port range to 27215 instead of 27016 and add 27215 to the cmd params.
[/QUOTE]

Originally I didn't have the range at 27005-27016, I had 27005 and 27015-27016.
But anyway, I tried using 27215 and it still didn't work, even after I tried forwarding not just that, but all 27005-27215 (yes i changed it to -port 27215 in cmd.)

EDIT: I left the server running on 27215 and someone joined... The internal IP is required to connect, which works with both ports. And why exactly could I previously connect to my own server with the external IP, but not now?
EDIT2: canyouseeme.org can see through 27015 and 27016 but not 27215 unforwarded. I still cannot connect using external ip. Kind of odd. Other people can connect with the old ports now... problem solved