Well maybe since no one answered this, people think it's a noob question, but I just encountered the same error message trying to disable dns relay in 1.21 firmware and this was the only post with the exact text Invalid lan ip address,ip adress in DHCP Server range.
So it turns out in my case, and probably others', the problem is that the router's IP address has to be outside of the DHCP address range in the DHCP Server Settings section which is right below the Router Settings section (where you are unchecking Enable DNS relay to create this problem) which is on the Setup -> Network Settingspage in the router's web setup. So I had 192.168.0.6 reserved for a device which means I didn't want to change the lower limit to 192.168.100, and my DIR-655 had an IP address of 192.169.0.1(which is what I wanted), and the default values for DHCP address range(or at least the values that I had at some previous point entered) are 192.168.0.1 to 192.168.0.255, and once I changed the lower limit to 192.168.0.2, it worked fine and let me save those settings and reboot.
It looks like the default values in 1.32 have 192.168.100 which may prevent this from happening to others with later firmwares.
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Topic: disabling dns relay (Read 5381 times)