Q: For MA5200F Version MA2.10-71xx configuration with loopback1 or loopback0, source address to RADIUS and L2TP source address are problematic.
If MA5200 Version MA2.10-71xx is not configured with loopback address, source address to RADIUS and nas-ip-address is address at upstream. If MA5200 Version MA2.10-71xx is configured with loopback0 address, packets to RADIUS are defaulted to use loopback0 as source address and so does L2TP.
If MA5200R007 is not configured with radius－server source interface loopback1, source address to RADIUS and nas-ip-address are addresses at upstream. If it is configures with it, use loopback1; for L2TP, use loopback1 as source address to send packets.