Using an OpenWRT router to provide multiple ports to an AREDN node that has a single POE network port
The Ubiquiti devices, with the exception of the AirRouter, have only have 1 network port. A switch with basic VLAN capability can be configured to have multiple ports and enable gateway (internet) access to your AREDN node. The AREDN node requires (on the port that it is connected to) traffic tagged as VLAN 1 for the Internet (WAN) and untagged for its own LAN network. And it wants DtD traffic to be tagged, on VLAN 2. Instead of using a NETGEAR 5-Port Gigabit Smart Managed Plus Switch for this, you could use an OpenWRT flashed WRT54G router, by configuring its switch. In the OpenWRT web user interface, set its LAN to be a DHCP client. The AREDN node will be the DHCP server. And go to the "switch" tab, and set things as below: (Be aware that the port numbers OpenWRT uses don't necessarily match the port numbers on the WRT54G router's case.) And be sure to have the router's CPU be on the untagged LAN VLAN, below that's the 0 VLAN (this is to allow you access to the router's web user interface in the future. The AREDN node will assign this router user interface web page its own LAN IP address). And if you enable the OpenWRT router's Wifi, any wireless devices that connect (if set to be DHCP clients) will also be assigned LAN IP addresss by the AREDN node.

Goal is to use an OpenWRT router to support a Bullet or an M900, instead of a Netgear Smart switch. Details follow.

On this OpenWRT router I went to its "switch" tab. And then I created an independent VLAN (VLAN 2, for DtD) that the main LAN (VLAN 0) won't "see" except inside the AREDN node. VLAN 1 will be the node's WAN (but do not confuse this WAN with the OpenWRT router's WAN). Okay, what did this get me as far as AREDN goes? These ports and VLANs will do the same thing we have Netgear smart switches doing. As most of us have WRT54Gs laying around... One port to feed the Bullet, another becomes the WAN for the Bullet, another the DtD port and others becomes the Bullet's LANs.

One thing to remember! Be sure you have the CPU "port" accessible to the Bullet's LAN, else you won't be able to reach the OpenWRT web GUI again!

Here is how we, in the OpenWRT router's GUI page for its switch (under Network and then under Switch), made an OpenWRT router act like a Netgear smart switch to service an AREDN node with just one ethernet jack, like a Bullet, to split off its WAN, LANs and DtD signals. At the switch tab, set things as below:

To set the OpenWRT router's LAN to be a DHCP client of the AREDN node, go in the OpenWRT web GUI for its LAN (under Network, then under Interfaces, and then click "edit" to the right of the LAM graphic box), and set it to be a DHCP client. The AREDN node will be the DHCP server. Don't do anything with the router's WAN here, it's not used (as we turned VLAN 1 off in the CPU port, this disconnects the OpenWRT router's WAN from this VLAN and thus from port 1).

If desired, the OpenWRT router's WiFi can be used as an AP to connect devices to the LAN. These devices will get their IP addresss (set the devices to be a DHCP client) from the Ubiquiti node. This is the non-ham radio FCC part 15 Wifi 802.11b/g. Go to the OpenWRT router's WiFi setup page, under "network" and then "wifi" to set it up as usual. under "Interface Configuration" (scroll down the eifi page a little) and then "network", you can select the network you want to attach to this wireless interface, likely already set to LAN.

Of course this is meaningful only if you happen to have some OpenWRT routers (like WRT54G's) laying around.... This OpenWRT router (a WRT54G V2.2) as a Netgear smart switch has worked fine 3 months now without any issues.

I did an additional mod to it, to have it run off the Ubiquiti POE power supply, and pass the POE to also power the Ubiquiti M900 node. I connected jumper wires between the ethernet jacks that are for the node, and the WAN connection, the blue and brown twisted pairs. Remove 75 ohm resistors RD13 and RD1, as these would introduce an unneeded extra load on the POE. And from the brown jumper wire I connected via a 5V 5W Zener diode to the router's ground, and from the blue jumper (the positive supply) a regular rectifier diode to the router's power rail (the WRT54G V2,2 uses a diode from the power jack to the internal power rail (protection from backwards wall warts, and here it keeps the POE from feeding into any Linksys wall wart that might still be plugged in the router)). As the router's internal DC-DC converters are rated a max of 24VDC, and the Ubiquiti POE brick produces 24VDC, I used these diodes to knock this 24V to 18V inside the router. I didn't want to run the converter chips on the edge... I attached some heat sinking to the Zener diode, on its leads I soldered some pieces of copper clad circuit board, it runs cool. The Ubiquiti POE brick has no problem with the extra load. And this means one less 120V brick in the shack.

And yet another mod is to make the router be able to pass the Ubiquiti POE brick reset signal to the Ubiquiti node. Ubiquiti uses a push button to introduce a small current onto the green and orange ethernet twisted pairs that a circuit in the node will use to trigger a reset. So one needs to connect the ethernet transformers' external windings center taps together (from the WAN port to the node port). You need to remove 75 ohm resistors RD14 and RD2. And connect a wire to one side of these surface mount pads (the pads that connect to the transformer centertaps). On the back of the board, connect a 0.1uF cap from the transformer TU3 centertap you just connected the jumper to, to ground. This reset signal is independent of the OpenWRT router's reset.