@Fabert 

Got it. Can I have the firmware version of the Archer C60? Does it mean that you can actually create more than 15 rules under " DHCP Server->Address reservation", but that will cause DHCP issue to all the clients in the network?

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@Kevin_Z Hi,

the firmware is the latest: 1.0.2 Build 20160811 rel.55127

 Concerning your question "Does it mean that you can actually create more than 15 rules under " DHCP Server->Address reservation", but that will cause DHCP issue to all the clients in the network?" The answer is: yes. The DNS especially is not assigned anymore. Then, the factory reset fixed it and I was able to add more than 15 entries in the Address Reservation. 

@Fabert 

Thanks. Can you respond to the email that I sent to you?

FWIW - I had this issue where DHCP seemed to suddenly stopped working.

I'm running an Archer MR600 with Firmware 1.2.0 0.9.1 v0001.0 Build 200511 Rel.44954n

I have a scheduled reboot every Monday as this router is located in a house that is empty 90% of the time. Last time it rebooted, nothing came back - no wifi network or anything - lights were on but nobody was home. So when next visited I did a physical reboot, seemed to come up, but nothing would connect. Manually configured my wifi ip settings, connected and found that the DHCP range was set to 192.168.0.100 - 192.168.0.200. The gateway ip and router address was 192.168.1.1/255.255.255.0 - So bizarrely the DHCP server was trying to serve addresses from a 192.168.0.0/24 range despite the fact it was running on a 192.168.1.0/24 network. I altered the DHCP address range, and bingo, everything worked.

No-one else touches this router, and I had never changed the DHCP settings on this pretty new box.