The 604 is administered entirely via web-browser, including firmware updating (once you download the firmware file). Opening the router's default address of 192.168.0.1 brings you to an opening screen (after you log in), where you can start an install wizard, or hit the controls directly.
Figure 1: WAN Settings
(click on the image for a full-sized view)
The 604 comes with its LAN DHCP server enabled and its WAN side set to be a DHCP client, which may enough for some users. But it also lets you set the router's Host Name or WAN MAC address (the two most common methods of non-PPPoE authentication) right on the Dynamic IP screen (shown in Figure 1 above). Selecting the other choices of Static IP or PPPoE change the screen to show the entries you'll need for those connection types. I found everything in this section to be logically organized, with decent on-line help on each screen to help newbies through the rough spots.
The overall responsiveness was good with screens coming up quickly. Clicking the Apply button for each screen required only a second or so wait for a confirmation screen before you could move to the next settings screen.
An interesting admin feature is the admin and user level access, with different logins. Both let you see all the screens, but you have to be logged in as admin to change anything. Remote administration can be enabled (it's off by default), and you can set the port and restrict access to a single IP address if you like. It's also nice that you can either reboot the router, or force it to reload factory defaults (although these functions are curiously on two different screens) via the admin interface.
The 604 allows multiple administrator logins at a time and doesn't provide any warning when an administrator joins the party. An omission is the fact that D-Link hasn't provided any way to log yourself out of the admin interface, and there's no time out either. The only way to "log off" is to quit your browser entirely (not just close the browser window that's opened to the admin interface). I hope this gets fixed in a future firmware upgrade.
NOTE! There's also a hardware reset-to-factory-defaults button on the back of the 604, but I found that if you followed the instructions in the manual, you will be forced to reload the firmware...which D-Link does not supply on the CD!
Just don't remove power from the router and press and hold the button for 5 seconds to get the normal reset function.
One other thing. If there are still any Netscape 4.7X users out there, you'll find problems viewing the admin screens. Switch over to Internet Explorer and all should be well. That's about it for the basics. Let's go check out the firewall's features...