I will use MacOS to dial VPN in the command line.
I provide my alias here, setting method:

 alias vpnlist=' scutil --nc list'
 alias vpn='networksetup -connectpppoeservice "Monitor"'
 alias vpnstop='scutil --nc stop Monitor'
 alias vpnstatus='networksetup -showpppoestatus "Monitor"'

Do not copy the name of the Monitor, it is the name I set, you can view the VPN you set by yourself with vpnlist.

Available network connection services in the current set (*=enabled):
* (Disconnected) 1AC8942C-7950-4E79-9422-10327900040D PPP --> L2TP "Monitor" [PPP:L2TP]

Set up an alias, when I need a vpn connection, Just use vpn to establish a connection.
For the first time, you need to manually connect and save the password

#Execute vpn alias
$vpn

#View vpn status
$vpnstatus
connected

#If you want to disconnect, just download
$vpnstop