New to Mikrotik and using it to fill a void in the ubiquiti product line. I need to create a backup LTE connection for a elevator emergency phone and need to conserve as much power as possible. If someone could advise if this is possible, would be much appreciated.
LAN NETWORK - > (Second Ethernet (POE OUT)) (SXT LTE KIT) Ethernet Port ONE POE → injector - > Grandstream ATA
What I’m hoping is that the SXT with router OS can have dual WAN. Main connection is the Lan network coming into Ethernet port two on the LTE modem. If that drops, it switches to the built in LTE. The voip adapter would be connected to main ethernet port.
The answer is not a simple yes or no.
It is a clear and loud yes for the ability to freely assign the logical role of the two Ethernet ports of the SXT LTE kit, and for the possibility to configure the Mikrotik to use the LTE as a backup of the primary WAN.
But as the external public IP changes once the traffic fails over to the LTE, the SIP exchange may reject calls coming from an IP from which it hasn’t received a registration before, so the service may be unavailable for minutes (until the re-registration takes place). Another thing is what happens if the failover takes place in the middle of an ongoing call, most exchanges won’t accommodate to that.
So the best solution has to be chosen depending on the properties of the particular SIP exchange and the particular ATA. A solution which doesn’t depend on any specific properties of the exchange and the ATA is to run a virtual router somewhere (ideally next to the exchange if you use your own one) and create two VPN tunnels from the SXT LTE kit, one via each WAN. The traffic of the phone will then prefer the VPN running via the Ethernet WAN, but if that one becomes unavailable, it will migrate to the LTE one in a few seconds. So the exchange will be receiving and sending the traffic from/to the same IP regardless which WAN will be active, so even a mid-call failover will cause just a short audio outage.
I’d also recommend to track the health of both WANs and send notification e-mails when one of them fails - a failover to a dead LTE is useless.