Reproducing steps:
set interfaces wireless wlan0 address 'dhcp' set interfaces wireless wlan0 disable set interfaces wireless wlan0 security wpa passphrase 'XXXXX' set interfaces wireless wlan0 ssid 'test' set interfaces wireless wlan0 type 'station' vyos@WIFI# sudo ip addr show dev wlan0 5: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000 link/ether cc:cc:02:84:cc:cc brd ff:ff:ff:ff:ff:ff inet 192.168.0.104/24 brd 192.168.0.255 scope global dynamic wlan0 valid_lft 172535sec preferred_lft 172535sec inet6 fecc::821f:2ff:fecc:cccc/64 scope link valid_lft forever preferred_lft forever