As i understand, In attached devices there are 3 devices connected.So you do not have any idea about the DGD3NM2J.
Before that I want to explain what is DHCP client list is..
Dhcp client means, The router assigns the ip address to the devices which are connected to it (wired or wireless).DHCP client is the devices that are getting IP address from the router.
I just want to know the wireless network on router is secured or not?
Waiting for reply.