我有一台 ubuntu 服务器，它应该通过 PPTP 保持与 itshidden.com VPN 的连接。不知何故，连接偶尔会中断，并且 /var/log/syslog 中会出现以下几行：
Jun 24 16:52:54 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0xa4f1
Jun 24 16:52:54 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0xa04a
Jun 24 16:52:54 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0xe49a
Jun 24 16:52:54 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0xed
Jun 24 16:52:54 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0xf9
Jun 24 16:52:54 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 'PPP Muxing' (0x59)
Jun 24 16:52:54 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0x8b
Jun 24 16:52:54 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0xec96
Jun 24 16:52:54 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0x11
Jun 24 16:52:54 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0xd64d
Jun 24 16:52:54 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 'Stampede Bridging' (0x6f)
Jun 24 16:52:55 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 'RTP IPHC Compressed non-TCP' (0x65)
Jun 24 16:52:55 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0xb
Jun 24 16:52:55 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0xc271
Jun 24 16:52:55 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0x4817
Jun 24 16:52:55 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0x9201
Jun 24 16:52:55 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0x2e34
Jun 24 16:52:55 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0x3
Jun 24 16:52:56 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0xfa32
Jun 24 16:52:56 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0x7c51
Jun 24 16:52:56 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0x64c8
Jun 24 16:52:56 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0x7
Jun 24 16:52:56 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0xf2e5
Jun 24 16:52:56 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 'Individual Link Encryption' (0x55)
Jun 24 16:52:56 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0x9
Jun 24 16:52:56 gbox-proxy20 pppd[613]: Protocol-Reject for unsupported protocol 0x407d
我的 /etc/ppp/peers/itshidden 文件是：
pty "pptp vpn-pay.itshidden.com --nolaunchpppd"
name itshidden
remotename PPTP
require-mppe-128
require-mschap-v2
file /etc/ppp/options.pptp
ipparam itshidden
defaultroute
noipdefault
persist
maxfail 0
lcp-echo-failure 10
lcp-echo-interval 5
user "*********************"
有什么建议么？
此外，lcp-echo-failure/lcp-echo-interval 参数似乎不起作用，因为我没有看到 ppp 重置。