Edit I've found a work-around. It's on page 2:
http://forums.dlink.com/index.php?topic=38542.msg128327#msg128327. Basically, use Virtual Server instead of Port Forwarding.
I'm having this really weird issue with my DIR-655 revB. I have some port forwarding rules set up and externally they work fine. However, if I try connecting to my IP address using those same ports from a computer within my LAN, it won't connect.
Externally, I can ping my WAN address and connect through forwarded ports. No problems.
Internally, pinging my WAN address apparently works (just now is the first time that's worked for me), however I can't access any of my computers using the WAN IP and port forwarded ports. I can access them by going directly to their hostnames or LAN IPs.
Things I've tried:
-Disabling/enabling firewalls on all computers involved
-Disabling/enabling QoS engine
-Disabling/enabling DNS relay
-Disabling/enabling Advanced DNS
-Adding custom nameservers from Google and Comodo
-Restarting computers
-Clearing DNS cache (I use a dynamic DNS name which works externally but not internally. This gets the correct IP internally and connecting directly to the IP doesn't work either.)
-Modifying the NAT Endpoint Filtering settings
I have an external DSL modem connected to the router using PPPoE if it matters.
The weird part is that it works externally but I've modified all of the values I can think of in the config with no luck. I upgraded to the DIR-655 from a DIR-615 which had all these settings in it and worked fine (until it started acting up which is why I replaced it).
Does anyone have any idea what I can do or what might cause this? I'm quite a tech savvy individual and it's very frustrating when nothing seems to work.
Thanks for your time.
Edit: Also, after looking at it, the router is set to ignore ping requests despite the fact that it does, indeed, seem to reply.