A simple AppleScript to prevent VPN session from timing out

macos-vpn-keepalive.scpt

on idle
  set checkIval to 60
  set vpnName to "YOUR_VPN_NAME"
  set pingDest to "PING_DEST_THRU_VPN"
	
  tell application "System Events"
    tell current location of network preferences
      set vpnConn to service vpnName
      if vpnConn is not null then
        if current configuration of vpnConn is connected then
          do shell script "ping -c 3 " & pingDest
        end if
      end if
    end tell
    return checkIval
  end tell
end idle