我正在尝试使用 strongswan 客户端将 Ubuntu Server 16.04 连接到 IPSec L2TP VPN。
显然连接建立成功，但没有创建接口 ppp0。
这是结果sudo ipsec up myconnection：
initiating Main Mode IKE_SA myconnection[2] to 116.38.129.101
generating ID_PROT request 0 [ SA V V V V ]
sending packet: from 192.168.0.104[500] to 116.38.129.101[500] (212 bytes)
received packet: from 116.38.129.101[500] to 192.168.0.104[500] (132 bytes)
parsed ID_PROT response 0 [ SA V V V ]
received NAT-T (RFC 3947) vendor ID
received XAuth vendor ID
received DPD vendor ID
generating ID_PROT request 0 …