@gerhard_meyer Don't use fibre + LTE as your primary failover in Sandton if you run 3CX voice calls; rather get two independent fibre FNOs entering the building on different ducts (for example MetroFibre on Link 1 and Vumatel/Openserve on Link 2) into a single MikroTik RB5009 router. Configure recursive routing with netwatch ping checks to 1.1.1.1 and 8.8.8.8 plus a script that flushes UDP SIP conntrack connections on failover. Your 3CX calls will recover in under 6 seconds with zero manual cable swapping.