The connection to the icom Connectivity Suite - VPN is established by calling the domain. The router must therefore be able to resolve this using a DNS. UDP port 53 must be opened to be able to reach a DNS server.
UDP port 1196 must be opened to establish a connection to the Init server (is used to download the configuration automatically) of the icom Connectivity Suite - VPN.
If a connection to an NTP server (used to update the router's system time) is required (if your router is located behind an external firewall and you are not using a local time server), UDP port 123 must be opened.
The VPN UDP port (alternatively: VPN TCP port) must also be opened for the productive operation of the router in the icom Connectivity Suite - VPN. You can find this in the icom Connectivity Suite on the My VPN Hub menu page.