[pptp-server] Error 720

[Alexander Polonsky]

Hi, Steven!

> You have to patch your kernel to support mppe encryption, which is the
> encryption part of poptop, and then patch ppp to support encryption as well.
> remember win2k doesnt have 128 bit encryption until you install the patch.
I have done this. ppp_mppe module seems to work, because I tried pptp
between Linux client and my PoPToP server - it works, and tcpdump shows
that the traffic is encrypted.

> besides that, your /etc/ppp/options.pptp file should look like this:
> 
> "
> lock
> debug
> name server
> auth
> require-chap
> nobsdcomp
> nodeflate
> #proxyarp
> 
> +chap
> +chapms
> +chapms-v2
> 
> mppe-40
> mppe-128
> mppe-stateless
> 
> # require-mppe
> "
> 
> so when you run the pptpd file, it should work straight away. Monitor the
> /var/log/messages file closely when your win boxes are connecting.  it
> should say mppe-40 or mppe-128 bit encryption when they connect.  If they
> dont connect, then disable "require encryption" and see if they connect, if
> they still dont connect then something is majorly wrong (ie did you do a
> killall pptpd and didnt type pptpd again?  ipchains rules too strong? etc).
> When you get it all worked out it should work sweetly.
I have changed options.pptp and disabled deflate and bsd compression, but
it doesn't help. As far as I know windows does not support both
compression types. The following line in log says that mppe level seems to
be ok:

Aug 27 11:27:28 nebel pppd[24620]: rcvd [CCP ConfAck id=0x3 <mppe 1 0 0 
20>]
Aug 27 11:27:28 nebel pppd[24620]: MPPE 40 bit, stateless compression
enabled

..but look further:

Aug 27 11:27:28 nebel pppd[24620]: rcvd [LCP TermReq id=0x4]
Aug 27 11:27:28 nebel pppd[24620]: LCP terminated by peer
Aug 27 11:27:28 nebel pppd[24620]: IPCP: Down event in state 1!
Aug 27 11:27:28 nebel pppd[24620]: Timeout 0x80503d4:0x80784c0 in 3
seconds.
Aug 27 11:27:28 nebel pppd[24620]: sent [LCP TermAck id=0x4]
Aug 27 11:27:28 nebel pptpd[24619]: CTRL: Received PPTP Control Message
(type: 12)
Aug 27 11:27:28 nebel pptpd[24619]: CTRL: Made a CALL DISCONNECT RPLY
packet

Seems like Windows drops LCP level without reason and shows error 720!!! 

I have also noticed that when encryption is completely off, Windows says
connection established, but does not initiate any IPCP negotiotions and
leaves PPP interface without IP address. This is OEM version of
german Win98se on laptop and I cannot find other windows boxes to try, so
I should set it up here.

Any ideas?

Thanks,
Alexander