To answer your questions:
- You do not need ports forwarded if using a LAN (i.e. same network)
- A second set of RRC's MUST use a unique set of port numbers different from the current set
- The SIP contact field must use the internal IP address of the radio RRC and NOT the dynamic DNS address.
Sometimes the DDNS will work if the ports are forwarded, but a good router will block this from working.
If you move the units offsite after changing the port numbers after port forwarding and testing, then the same
DDNS address can be used as the SIP address as the first units, since the port numbers will be passed onto the
correct set.
73,
Mitch DJ0QN / K7DX