I would like to narrow down the issue with the DIR-685 DHCP Server, and I believe the DNS Relay setting in Network Setup is the problem. I'm just going to post out on what I've found for anyone that is interested to try out.
After finally getting the chance to test the router, and the first thing I done was connecting my laptop without a static I.P letting the DHCP server to allocate the I.P. But as usual it will allocate a random one, which isn't in the DHCP table. This will only happen to people if they leave the router for more than 24 hours. So if I enable an static I.P within the DHCP table it works like a charm, but I don't like to set the static I.P manually everytime I decide to connect to a D-Link router. But if I disable the static and assign the DNS to the router, I have connection to the router? But it will just provide an random I.P outside the DHCP table, which would prevent me connecting on to the internet. As I kept toggling settings, I wondered what would happen with disabling the DNS Relay. After disabling the DNS relay I put auto I.P and within a few moment, the out of range DHCP was corrected.
The DNS Relay is a method of caching DNS queries, to shorting down response time. But I think that the memory allocated gets full and effects the DHCP server? Anyone can shed some light on this. or perhaps test this out? But I don't know how long the effect are, or whether it just cleared the cache, as I just done the test now.
This problem effect me and my friend (on a different D-Link model), and I would like to know why.
FurryNutz: Not sure why you locked the thread, but started a new one.... The reason that I don't speak to D-Link themselves is due to not having the product with me, I work away from home. And I want to narrow the issue before I speak to them. This test would help if any other users that is effected by this can help
Update:
With the DNS Relay Off, it will automatically disable the "Advanced DNS Service" (Found in Internet Setup) which could also be causing the issue.
So far all my mobile devices now works without static I.P, I'm going to leave this here.....though I wish I've figured this out earlier, didn't think the relay was useless.
Connections:
Modem- 2xVirgin Super Hub Netgear VMDG480
- Motorola SURFboard SB5101U (Previously same problem, used with 10Mb connection)
ISP:- Virgin Media 30Mb connection
- Virgin Media 100Mb connection (My friend)
Router:- DIR-685 Hardware Version: A1 Firmware Version :2.01 , Wed 09 Mar 2011
- DIR-815 Hardware Version: A1 Firmware Version :1.00 Fri 06 Aug 2010
Virgin Media DNS servers:
194.168.4.100
194.168.8.100
Ping is now lower 20 ms (DNS Relay OFF) compared to 35 ms (DNS Relay ON)
Update: Next Day (Est. 20 Hours with DNS Relay off and no reboot)
While my mobile device was still connected to the WiFi over night, the connection was fine. But then I decided to turn the WiFi off and on, the mobile had trouble obtaining I.P address again

. Didn't help I forgot to get the log setting on, but not sure if it was a fair test consider the DHCP Server was on for 10 days. Turning the DNS Relay off didn't rebooted the router, so I figure I change the internet setup, dynamic IP and input the DNS Server manually.
Primary DNS Address : 194.168.4.100
Secondary DNS Address : 194.168.8.100
MTU : 1500
Will give the router an full shut down, and ask my brother to continue monitoring the router. As I'm away in the weekdays... but toggling the DNS Relay seems to clear the cache needed for the DHCP to function again.
Anyway if anyone can help do the following:
Instructions:- Setup > Network Setup > Router Settings Enable DNS Relay = unticked
- Check that the DHCP is working, post your results
- Reboot Router
Effects:- Lower ping
