By the way, my Ipad detect my openwrt network with the following specifications :
IP adress : 192.168.2.116
Subnet Mask : 255.255.255.0
Router : 192.168.2.27
DNS : 192.168.2.27
IP adress : 192.168.2.116
Subnet Mask : 255.255.255.0
Router : 192.168.2.27
DNS : 192.168.2.27