Asus RT-AC66U - Manual (Page 64)

4.2.2 DHCP Server
Your wireless router uses DHCP to assign IP addresses
automatically on your network. You can specify the IP address
range and lease time for the clients on your network.
To configure the DHCP server:
1. From the navigation panel, go to Advanced Settings > LAN >
DHCP Server tab.
2. In the Enable the DHCP Server item, tick Yes.
3. In the Domain Name text box, enter a domain name for the
wireless router.
4. In the IP Pool Starting Address item, key in the starting IP
address.
5. In the IP Pool Ending Address item, key in the ending IP
address.
6. In the Lease Time item, specify in seconds when an assigned
IP address will expire. Once it reaches this time limit, the DHCP
server will then assign a new IP address.