I have a T-Mobile router (G4AR - 5G) with a T-mobile SIM providing 5G service (through Calyx BYOD, not TMHI).
I prefer running wireless networks off my Max Transit (MAX-TST-GLTE-G-T-PRM running latest firmware 8.5.5) - and I also have a OpenVPN client to Proton on one of the networks.
Primary WAN connection is LAN (TMo) to WAN (Peplink) - using Ethernet cable (not sure what spec). Bandwidth is set to 100 Gig; physical port is set to auto-negotiate, with MTU/MSS set to 1360/1320 (based on optimal packet size, based on ping fragmentation flag).
Secondary WAN connection is WiFi WAN to TMo 5ghz wifi.
When connecting directly to the G4AR wireless network, speeds are sometimes 2-3x faster than speeds when connecting to the Peplink wireless networks (doing back-to-back speed tests connecting to each network in turn).
Max speeds I’m getting on the TMO wifi are about 100 Mbps, so I wouldn’t think data throughput is an issue (Max Transit is meant to support 400 Mbps).
Not sure if there is something I’m missing that would slow down the Ethernet connection.
Thoughts?