Yes, you can use pretty much any UDP port you want. It needs to be unused (so steer away from the well-known UDP ports), your provider needs to allow incoming and outgoing connections on it, and you need to setup port forwarding if your MX is behind a NAT router.   The 48822 is a port that is dynamically chosen by the MX from the range 32768-61000. This is for the automatic NAT traversal process. For the manual NAT traversal configuration you're free to use ports from outside that range. ... View more

You don't need to add exceptions to the firewall for the VPN tunnels to work. The MX allows its own VPN tunnels automatically. ... View more