I have a router that is set up as a l2tp Server with the simple queue for inbound client connections
Means L2TP Server, He should have Public IP.
and I am trying to properly setup a RBLHGR&R11e-LTE radio that automatically gets assigned a private IP address when connected to the local tower.
This should be a L2TP Client, true? Then he can receive from ISP private IP or Public IP - anyway he must have internet with any IPv4 IP address.
What is the best way to go about setting this up so that it automatically connects to my VPN server even if the IP changes on the radio side?
Only L2TP Server must have Public IP and it can be dynamic. Then at MikroTik you can enable Cloud feature.
WinBox > IP > Cloud
This give you a uniq DDNS hostname who will be show your current Public IP.
I have setup a client router with a private static IP address and it works fine,
I should be fine. L2TP client must have access to his L2TP Server at his current Public IP and do vpn connection.
but it seems that if I don't have a static connection, the distance route setup for the lte connection and the client router reverts back to its default route.
?? Re-Write with other words.
For example, I have the VPN client setup to have the default distance route to "1" and the LTE default distance route set to "2" to establish the VPN connection. But as soon as I reboot the radio, the LTE reverts back to "1" and then the radio will not connect to the VPN server.
??
Give us the /ip route print when you have internet and when you haven't internet.
I can only speculate. Give export / print from route to answer you.