Advanced users can optionally customize IKEv2 options.
Advanced users can optionally specify a DNS name for the IKEv2 server address. 
The DNS name must be a fully qualified domain name (FQDN). Example:

sudo VPN_DNS_NAME='vpn.example.com' sh vpn.sh

Similarly, you may specify a name for the first IKEv2 client. 
The default is vpnclient if not specified.

sudo VPN_CLIENT_NAME='your_client_name' sh vpn.sh

By default, clients are set to use Google Public DNS when the VPN is active. 
You may specify custom DNS server(s) for all VPN modes. Example:

sudo VPN_DNS_SRV1=1.1.1.1 VPN_DNS_SRV2=1.0.0.1 sh vpn.sh

By default, no password is required when importing IKEv2 client configuration. 
You can choose to protect client config files using a random password.

sudo VPN_PROTECT_CONFIG=yes sh vpn.sh