About to file a bug, but looking to see if this is happening to anyone else.
I recently got a couple AR-300M routers and loaded the latest version of OpenWRT on them, but I've found that after a fairly simple configuration through LuCI, DHCP does not start unless there is a cable plugged into the LAN port.
The bug seems identical to this one: https://bugs.openwrt.org/index.php?do=details&task_id=763&status=
and while that mentions it was fixed, I still see the issue in this version (OpenWrt 18.06.1 r7258-5eb055306f)
Basically, after simply joining a wifi network and adding a network to be broadcast, DHCP stops offering IPv4 addresses to clients until the service is restarted. Rebooting the device any number of times does not help, only setting a manual IP, SSHing in and restarting dnsmasq fixes the issue temporarily, until the next reboot.
If a network cable is plugged into the LAN port, DHCP is offered after the device is reset.
It seems like odhcp does not start correctly even though the wireless radio joins the network upstream, leaving the device dead in the water until it's reset with a LAN cable attached or the dnsmasq service is restarted.
Anyone else having this problem?