Thank Pascal Hambourg! pptp-linux provides pptpsetup command. I run pptpsetup with some options and it displays:
Using interface ppp0 Connect: ppp0 <--> /dev/pts/1 CHAP authentication succeeded MPPE 128-bit stateless compression enabled local IP address 192.168.115.34 remote IP address 192.168.115.1 It seems that not every thing has been set up.
