Just a quick tip:
command to see all alive devices IP connected to openwrt router from shell:
opkg update
opkg install fping
fping -a -q -g 192.168.1.0/24
example:
root@OpenWrt:~# /usr/bin/fping -a -q -g 192.168.1.0/24
192.168.1.20
192.168.1.21
192.168.1.103
192.168.1.131
192.168.1.138
192.168.1.143
192.168.1.162
192.168.1.174
192.168.1.180
192.168.1.178
192.168.1.175
192.168.1.177
192.168.1.192
192.168.1.229
192.168.1.226
192.168.1.239
192.168.1.254
192.168.1.252
192.168.1.245