I have a Titan Wireless TW-533-4 (Intel IPX425) running 17.04.1 (https://openwrt.org/toh/zinwell/zw4400). It has two Fast Ethernet ports: eth0 (LAN) and eth1 (WAN).
I have an odd issue that if I unplug the LAN, my WAN no longer possesses an IP Address, and therefore my wireless LAN cannot reach the Internet.
I'm not sure if this is some protection for the Power-over-Ethernet, as I can't connect eth1 directly to an Atheros switch port in another device, without the 'circuit breaker' cutting the board off...perhaps 0 must always be connected before 1???
The log states when unplugging eth0 (relevant entries):
- Network device 'eth1' link is down
- connectivity loss on interface wan
- eth1 link down
- lastly: eth0 link down
- then: DHCP packet received on eth1 which has no address
EDIT: I also notice that, if I use eth1 for the PoE and I disconnect the Ethernet side of the jack, eth1 remains up and frozen in OpenWRT (Tx with no Rx). I believe this might be a circuit breaker issue. I discovered this because I had to use the PoE adapter in order to connect to an upstream Atheros switch.