[pptp-server] gre running over ppp or IP?

[Justin Kreger]

The ppp session is inside the gre tunnel, which is encapsulated in IP.  As
for your request time outs, you may not have pppd setup to be the server,
it may think its a client... along with your client.

Justin Kreger, MCP MCSE CCNA
jkreger at earthling.2y.net jwkreger at uncg.edu jkreger at aristotle.wss.net


On Wed, 23 May 2001, Ismandy Ali wrote:

> Hi all,
> 
> I know that  the pptpd needs port 1723 and protocol 47 to work.
> 
> I followed the howto from http://www.vibres.com/pptpd/example.html
> -------------------
> ppp-2.3.11.tar.gz
> Apply ppp-2.3.11-openssl-0.9.5-mppe.patch.gz patch to ppp-2.3.11
> Apply ppp_mppe_compressed_data_fix.diff patch to the
> ppp-2.3.11/linux/ppp_mppe.c file (after the openssl-mppe patch is
> applied)
> if_ppp_2.2.17.diff (used to patch the Linux source after ppp-2.3.11
> makes it's changes)
> pptpd-1.1.2.tar.gz
> kernel linux-2.2.17.tar.gz
> ----------------------
> 
> In our pptpd, correct me if I am wrong, should the GRE is encapsulated
> and running over IP. But based from the the output captured by my
> tcpdump, it seems that  GRE   is not running over IP, instead it is
> running over PPP(0x880B). So is this the correct way of pptpd works?
> 
> My pptpd does n't works, and it gives me  "LCP: timeout sending
> Config-Requests" inside my logs file,and from the FAQ, is says that this
> problem  occured due to the filtering on the firewall. I don't think it
> is be the problem since we does n't implement any form of filtering in
> our network.
> 
> Any idea what cause such problem?
> 
> 
>  #tcpdump -i eth0 -n proto 47 or port 1723
> 
> 17:44:48.199173 < 161.142.45.174.1553 > 161.184.155.230.1723: S
> 10498228:10498228(0) win 8192 <mss 536,nop,nop,sackOK> (DF)
> 17:44:48.199310 > 161.184.155.230.1723 > 161.142.45.174.1553: S
> 3073208334:3073208334(0) ack 10498229 win 32696 <mss 536,nop,nop,sackOK>
> (DF)
> 17:44:48.483929 < 161.142.45.174.1553 > 161.184.155.230.1723: . 1:1(0)
> ack 1 win 8576 (DF)
> 17:44:48.526568 < 161.142.45.174.1553 > 161.184.155.230.1723: P
> 1:157(156) ack 1 win 8576 (DF)
> 17:44:48.526611 > 161.184.155.230.1723 > 161.142.45.174.1553: . 1:1(0)
> ack 157 win 32540 (DF)
> 17:44:48.526916 > 161.184.155.230.1723 > 161.142.45.174.1553: P
> 1:157(156) ack 157 win 32696 (DF)
> 17:44:48.880168 < 161.142.45.174.1553 > 161.184.155.230.1723: P
> 157:325(168) ack 157 win 8420 (DF)
> 17:44:48.884505 > 161.184.155.230.1723 > 161.142.45.174.1553: P
> 157:189(32) ack 325 win 32696 (DF)
> 17:44:48.889345 > gre-proto-0x880B (gre encap)
> 17:44:49.298740 < 161.142.45.174.1553 > 161.184.155.230.1723: .
> 325:325(0) ack 189 win 8388 (DF)
> 17:44:51.894451 > gre-proto-0x880B (gre encap)
> 17:44:54.904470 > gre-proto-0x880B (gre encap)
> 17:44:57.914381 > gre-proto-0x880B (gre encap)
> 17:45:00.924388 > gre-proto-0x880B (gre encap)
> 17:45:03.934683 > gre-proto-0x880B (gre encap)
> 
> p/s: I learn tcpdump from  problem, it is fun, and I need people to ask.
> Not that I am dunnot know, but I am not sure.
> 
> Kukulkan
> 
> 
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