давно есть такая проблема:

pptp m call topnet
using channel 38
Using interface ppp0
Connect: ppp0 <--> /dev/pts/7
sent [LCP ConfReq id=0x1 <mru 1000> <asyncmap 0x0> <magic 0xa1ab61c7> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x1 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfAck id=0x1 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfReq id=0x1 <mru 1000> <asyncmap 0x0> <magic 0xa1ab61c7> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x2 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfAck id=0x2 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfReq id=0x1 <mru 1000> <asyncmap 0x0> <magic 0xa1ab61c7> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x3 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfAck id=0x3 <auth chap MS> <magic 0x68c5d1f0>]
rcvd [LCP ConfReq id=0x4 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfAck id=0x4 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfReq id=0x1 <mru 1000> <asyncmap 0x0> <magic 0xa1ab61c7> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x5 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfAck id=0x5 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfReq id=0x1 <mru 1000> <asyncmap 0x0> <magic 0xa1ab61c7> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x6 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfAck id=0x6 <auth chap MS> <magic 0x68c5d1f0>]
rcvd [LCP ConfReq id=0x7 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfAck id=0x7 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfReq id=0x1 <mru 1000> <asyncmap 0x0> <magic 0xa1ab61c7> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x8 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfAck id=0x8 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfReq id=0x1 <mru 1000> <asyncmap 0x0> <magic 0xa1ab61c7> <pcomp> <accomp>]
rcvd [LCP ConfReq id=0x9 <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfAck id=0x9 <auth chap MS> <magic 0x68c5d1f0>]
rcvd [LCP ConfReq id=0xa <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfAck id=0xa <auth chap MS> <magic 0x68c5d1f0>]
sent [LCP ConfReq id=0x1 <mru 1000> <asyncmap 0x0> <magic 0xa1ab61c7> <pcomp> <accomp>]
rcvd [LCP TermReq id=0xa]
sent [LCP TermAck id=0xa]
Terminating on signal 15
sent [LCP TermReq id=0x2 "User request"]
sent [LCP TermReq id=0x3 "User request"]
Connection terminated.
Modem hangup
mows ~ #

как лечиться?
mows ~ # pptp --version
pptp version 1.7.1
mows ~ # pppd --version
pppd version 2.4.3
mows ~ # uname -a
Linux mows 2.6.15-suspend2-r8 #1 SMP PREEMPT Thu Mar 9 05:49:01 YEKT 2006 i686 Intel(R) Pentium(R) 4 CPU 2.80GHz GNU/Linux
mows ~ #

m - cisco 831.