I'm replacing my DGL-4100 with a DIR-657. I've used several DLink routers over the years, and this is the first time I've had a problem.
DIR-657
HW Version A1
FM Version 1.02 (also tried 1.01)
Charter Internet (Missouri) with Motorola SB-6121
Ooma Telo between Modem and router (suggested setup from Ooma)
My DGL-4100 is setup with DHCP. The Ooma Telo assigns the IP address. The only thing other thing I've done is specifically assigned Charter's DNS servers. The system has been solid with the Ooma.
I've tried placing the DIR-657 in place of the DGL-4100. Although the status page showed connection, I couldn't connect to anything via the WAN connection. I even tried the setup without the Ooma with same result. I tried several times, rebooting the entire setup, factory reset and reconfiguration, etc using the software cd, built in wizards, and manual configuration. I finally got it to work (no idea why it did). The setup was Modem->Ooma->DIR-657. That worked for a few days until we had a power failure. Restarting all or each component in order did not restore internet connection - I had the same situation as I did during installation.
I updated firmware to 1.02, did a factory reset, and set everything up again (including DHCP reservations). I was able to connect to the internet again. Yesterday, I lost internet connection again. Restarting the DIR-657 did not restore it.
I can put my DGL-4100 in place of the DIR-657 and restore connection.
It appears that the WAN port on the DIR-657 loses connection.
The Ooma has a web interface that I can access with it's IP address. I've gone into that interface via the DGL-4100 and checked it. It has DHCP which assigns the address to the router. It has DMZ capability. Changed the configuration to place an IP address in the DMZ. I then swapped out the DGL-4100 with the DIR-657 and configured the DIR-657 with a static IP address (from the DMZ). Still no luck with internet connectivity. I've gone back to DHCP. The status screen shows connection, just no internet. I've used both Charter's DNS servers and Google.
I'm using wired and wireless systems to check connectivity. I'm not even looking at the wireless aspects of the router at this point, just trying to get internet connectivity via wire.