求助：关于嵌入式pptp拔号时 LCP协商超时的问题

开发一个路由器，采用linux kernel 2.6.24,pppd v2.4.4, pptp1.7.1
联通3g拔号上网模块，当我用PC通过路由器连接可以正常连接到PPTP服务器。
如果在路由器里面直接pptp拔号，则会提示LCP超时。

执行pptp拔号的命令如下：
pppd pty "pptp xx.xx.xx.xx --nolaunchpppd" nodetach debug user test password 1234 default-asyncmap noendpoint mru 1400
using channel 8
Using interface ppp1
Connect: ppp1 <--> /dev/pts/0
sent [LCP ConfReq id=0x1 <mru 1400> <magic 0x8e664ceb> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x1 <mru 1400> <auth chap MD5> <endpoint [local:49.6e.63.6f.6d.69.6e.67]>]
sent [LCP ConfRej id=0x1 <endpoint [local:49.6e.63.6f.6d.69.6e.67]>]
rcvd [LCP ConfRej id=0x1 <pcomp> <accomp>]
sent [LCP ConfReq id=0x2 <mru 1400> <magic 0x8e664ceb>]
sent [LCP ConfReq id=0x2 <mru 1400> <magic 0x8e664ceb>]
rcvd [LCP ConfReq id=0x1 <mru 1400> <auth chap MD5> <endpoint [local:49.6e.63.6f.6d.69.6e.67]>]
sent [LCP ConfRej id=0x1 <endpoint [local:49.6e.63.6f.6d.69.6e.67]>]
sent [LCP ConfReq id=0x2 <mru 1400> <magic 0x8e664ceb>]
sent [LCP ConfReq id=0x2 <mru 1400> <magic 0x8e664ceb>]
sent [LCP ConfReq id=0x2 <mru 1400> <magic 0x8e664ceb>]
rcvd [LCP ConfReq id=0x1 <mru 1400> <auth chap MD5> <endpoint [local:49.6e.63.6f.6d.69.6e.67]>]
sent [LCP ConfRej id=0x1 <endpoint [local:49.6e.63.6f.6d.69.6e.67]>]
sent [LCP ConfReq id=0x2 <mru 1400> <magic 0x8e664ceb>]
rcvd [LCP ConfReq id=0x1 <mru 1400> <auth chap MD5> <endpoint [local:49.6e.63.6f.6d.69.6e.67]>]
sent [LCP ConfRej id=0x1 <endpoint [local:49.6e.63.6f.6d.69.6e.67]>]
sent [LCP ConfReq id=0x2 <mru 1400> <magic 0x8e664ceb>]
rcvd [LCP ConfReq id=0x1 <mru 1400> <auth chap MD5> <endpoint [local:49.6e.63.6f.6d.69.6e.67]>]
sent [LCP ConfRej id=0x1 <endpoint [local:49.6e.63.6f.6d.69.6e.67]>]
sent [LCP ConfReq id=0x2 <mru 1400> <magic 0x8e664ceb>]
rcvd [LCP ConfReq id=0x1 <mru 1400> <auth chap MD5> <endpoint [local:49.6e.63.6f.6d.69.6e.67]>]
sent [LCP ConfRej id=0x1 <endpoint [local:49.6e.63.6f.6d.69.6e.67]>]
sent [LCP ConfReq id=0x2 <mru 1400> <magic 0x8e664ceb>]
sent [LCP ConfReq id=0x2 <mru 1400> <magic 0x8e664ceb>]
rcvd [LCP ConfReq id=0x1 <mru 1400> <auth chap MD5> <endpoint [local:49.6e.63.6f.6d.69.6e.67]>]
sent [LCP ConfRej id=0x1 <endpoint [local:49.6e.63.6f.6d.69.6e.67]>]
LCP: timeout sending Config-Requests == 超时
Connection terminated.
Modem hangup
Waiting for 1 child processes...
script pptp xx.xx.xx.xx --nolaunchpppd, pid 979
Script pptp xx.xx.xx.xx --nolaunchpppd finished (pid 979), status = 0x0

路由信息如下：
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
10.64.64.64 0.0.0.0 255.255.255.255 UH 0 0 0 ppp0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
127.0.0.0 0.0.0.0 255.255.255.0 U 0 0 0 lo
0.0.0.0 0.0.0.0 0.0.0.0 U 0 0 0 ppp0

顶，我也遇到同样的问题，window上貌似是可以的。