Background

The Ubiquiti UDM-Pro is a wonderful beast – everything you’d rationally want in a great, secure, high performance, feature-rich network router with a truly corporate grade feature set. In combination with Ubiquiti UniFI Switches and UniFI Access Points, the result is a capability to set up and run a network with something remarkably close to ‘the greatest of ease’.

The servers and services it makes available used to require days of head-scratching and a Unix command line. Instead, with this equipment, it takes a few hours and an iPhone App (for initial super-easy UDM-Pro configuration) and includes an excellent web interface (with secure remote access also available) for ongoing management.

For sites with lots of access points, it just doesn’t get easier than this – and the performance is excellent.

One thing I wanted to do with my (so far) two sites running this combination of equipment (UDM-Pro, UniFI switches and UniFI wireless Access Points) is to have a solid and seamless 4G 4G/LTE backup (Failover) path configured in and operating, for those times when the primary network connection is down.

Over time, I have cranked through quite a list of brands of both ethernet-to-4G gadgets, and (for a regional site I run), I had also cranked through lots of 4G diversity antennas, trying to find a good one.

In the hope of saving others the same expenditure of time, money, and experimentation, I am documenting the combination that is working (really well!) for me.

The barriers to a good experience in this regard are twofold. When it comes to a 4G-Ethernet ‘modem’, you need one that is fast, reliable, supports external diversity antennas, and (critically) supports ‘bridging’ of the 4G connection through to the ethernet port.

I’ve gone through a lot of (in hindsight) rubbish antennas before I found a good one, and I’ve also gone through a number of 4G/Ethernet routers that are either a bit rubbish and/or that insist on inserting their own layer 3 routing table into the data path, adding other /24 network range, more complexity, and becoming a barrier to direct end-to-end-access from the UDM-Pro to the 4G/LTE network provider.

The Parts List

Here are the devices that have worked (really well!) for me… after a trying a lot that did not work well or (in most cases) just did not work at all!

4G/Ethernet modem

The device of choice for me – after a lot of trial and time – is the Netgear 4G LTE Modem with Dual Ethernet Ports .

This model is available at Officeworks for A$249 (though I found you ‘had to ask’ – it was behind the front counter, not on the in-store shelving – perhaps because it is a relatively expensive and yet relatively small, hence steal-able box).

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The unit has exactly what you need and nothing you don’t. There’s a LAN ethernet port (and a WAN one we don’t need to use for this application), and there is no WiFi (not needed, and just a distraction in practice to have it in there and to have to turn it off).

This unit takes a standard 4G/LTE SIM directly. This goes into little socket arrangement in the base of the unit is a touch non-obvious in terms of how to load and lock-in the SIM. That said, there is a little cardboard guide sheet stuck in the SIM slot to help you to work it out. You open the sliding cover, lay the SIM down on the pins in the box, close the cover and slide it up to lock it.

I configured it at first with my Mac, using a USB-Ethernet dongle cabled directly to the unit with a (supplied) patch lead.

In terms of configuration: With a Telstra SIM installed, it was 100% instant plug-and-play, coming up initially on 192.168.5.1 and logged in using the password printed on the back of the box.

I did a firmware update (on general principles) – downloading via the LTE network to do it.

Then I simply switched the unit from router mode to ‘bridge’ mode. This is the key to a very simple life!

After rebooting into Bridge mode, the unit came up on my Mac with the Telstra 4G IP address attached directly to my Mac, fully automatically – exactly what I wanted to see. Zero configuration, and 192.168.x.x network is gone (so it is not, in any sense, ‘in the way’).

Ubiquiti SFP Ethernet Transceiver Module (for the WAN2 port)

When connecting the UDM-Pro to an Internet link, the primary port (designated “WAN(1)” must to be physical port #9. It cannot be any other port on the device (at least, not without behind-the-scenes internal configuration hackery I didn’t want or need to undertake).

Port 9 is a Gig-E port, so that is easily used to connect to (in my case) an Aussie Broadband NBN based Internet service.

In one site, I’m using an Aussie Broadband HFC connection which is direct plug-and-play – literally plug in a patch lead between port 9 on the UDM-Pro and the back of the Arris HFC modem supplied by NBNCo, and the Internet link ‘just works’… zero setup, zero complication. Just instant Internet. Win!

The WAN2 port (failover) port on the UDM-Pro is also a locked-in thing – it has to be Port 10.

As it happens, Port 10 is an SFP socket, not a Gig-E port.

What you need to buy to deal with that is a “Ubiquiti RJ45 – SFP Transceiver Module , SFP to RJ45 1G”

This module, available for $27 from Wireless4Now, plugs into the SFP socket on the UDM-Pro and turns that SFP socket into a standard RJ45 Gig-E port.

High Performance Outdoor 4G / LTE MIMO Antenna Set (optional)

In one site, in a city location, no external 4G antenna was needed with the LB2120 for entirely acceptable performance (30 megabits per second plus – entirely good enough for a failover link!)

In another (regional) site I’ve deployed this equipment into, however, the 4G tower site is several kilometres away (and the networking gear is in an outdoor metal cabinet). There is good line of sight, but at this sort of distance a simple omni-directional antenna doesn’t cut the mustard to get decent performance – its time to bring out the big guns.

After many false starts, I have found a specific antenna and cable combination that rocks. It is not cheap, but… boy does it work. It took my 4G site performance from 1 bar to 5 bars. It took the real world performance up from around 8-10 megabits per second into the 60-70 Megabit per second range (!).

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The antenna kit that did the trick for me is a properly aligned (2 x 45 degree offset) pair of serious Yagi antennas, a suitable mount to achieve that alignment, a backhaul cable, and a 2 x TS9 adaptor tail set to suit the NetGear LB 2120’s on-board TS-9 sockets.

This setup is not cheap – running to a bit more than $600, from RFShop in Adelaide.

It is, however, absolutely worth it if you want to maximise your regional link performance, and the outcome, for me, was a dramatic improvement. This was achieved after multiple attempts with less ‘serious’ antenna sets (that either did nothing for me, or in some cases actually made the performance substantially worse)

The one other item that was helpful in mounting that Yagi combination (which is quite heavy) was a short ‘TV’ antenna mounting bracket, that turned out to be perfect for the job, for another A$27 from Bunnings Aerospace 🙂

Configuration

Configuration of the failover path was trivial – due to using equipment that ‘just works’ 🙂

Indeed, it was totally plug-and-play. I just inserted the SFP module, plugged the Netgear device in (after first testing on my Mac as noted above), and that was it.

On the UniFI web interface, I selected the UDM-Pro and checked the characteristics for WAN2… bingo, already up and running!

Testing?

That is as simple as unplugging the primary (NBN) cable, observing that the Internet keeps right on going, and doing some speed tests to compare-and-contrast. When done, plug the NBN cable back in.