I live in a rural area in the UK so even though I am lucky enough to have OpenReach FTTP (Fibre to the Premises) I usually have a number of outages each year due to OpenReach doing work or physical damage happening to the cables strung along the power poles (usually due to trees). I also have a UniFi home network setup with a UniFi Security Gateway, which natively supports having two WAN connections, so I finally decided to setup a secondary 4G/LTE connection to have failover for when I lose my main connection.

I originally tried this with a D-Link 4G router, however that didn’t reliably connect to the 4G, so I ended up going with a TP-Link TL-MR6400 4G Wi-Fi Router with a GiffGaff SIM. I chose GiffGaff because I have reasonable O2 Network signal in my area, and this would allow me to have a month to month data arrangement that I can ramp up and down as needed. In my case I usually have this on a £10/month package in order to have 20Gb of data available, which should get me through a rainy day of the kids watching iPads if needed.

The Unifi Security Gateway I’m using has three interfaces - I am using WAN1 as my primary Internet connection, LAN1 as the port for my internal network, and I’ve enabled WAN2/LAN2 as my secondary WAN port in “Failover only” mode as follows: Setup for LTE Backup Interface

Once this is done, you should be able to check to see this is all working if you SSH into your UniFi Security Gateway as follows:

admin@Gateway:~$ show load-balance watchdog
Group wan_failover
  eth0
  status: Running
  pings: 14941
  fails: 0
  run fails: 0/3
  route drops: 0
  ping gateway: ping.ubnt.com - REACHABLE

  eth2
  status: Running
  failover-only mode
  pings: 14869
  fails: 228
  run fails: 0/3
  route drops: 0
  ping gateway: ping.ubnt.com - REACHABLE

And also be able to see interface flow stats:

admin@Gateway:~$ show load-balance status
Group wan_failover
  interface   : eth0
  carrier     : up
  status      : active
  gateway     : X.X.X.X
  route table : 201
  weight      : 100%
  flows
      WAN Out : 1236000
      WAN In  : 1465
    Local Out : 826

  interface   : eth2
  carrier     : up
  status      : failover
  gateway     : X.X.X.X
  route table : 202
  weight      : 0%
  flows
      WAN Out : 0
      WAN In  : 0
    Local Out : 0

Note that if you have two full time Internet connections, it will also fail over correctly in the event that one of those connections goes down. I haven’t chosen to do that because my primary connection is much faster than the backup, and I choose to only have it online for when the faster one goes down.