When Yun reflash or reset factory default or brand new:

reset factory default by:

reset-to-factory-anyway
reboot

Yun network setting:

wlan (WIFI) 

mode:Access Point

static ip:192.168.240.1 

eth1 (ethernet)

dhcp client get ip from router ip pool

(192.168.0.X)

backup system wide setting:

uci export > /root/ap.conf

whenever you need restore it:

uci import </root/ap.conf
reboot