PPTP with Centos Server & Win 7 client not providing default gateway

cerien · 08-21-2013, 11:19 AM

I am trying to setup a Centos 5.8 box as a PPTP server - it worked in the past and no longer does.

My issue is that the client (win7) receives 0.0.0.0 as default gateway and hence cant route anything. Cant ping the Centos box on the vpn @, cant access the web. When I uncheck the use default gateway box from win7, I can reach the Centos box.

I've disabled (temporarily) all iptables rules but the -A POSTROUTING -o eth0 -j MASQUERADE - I have /proc/sys/net/ipv4/ip_forward set to 1

Any suggestion as how can the server provide a correct gateway address to the client ?

Tks in advance

pptp version is 1.7.2-8.el5

Gad · 08-22-2013, 12:59 PM

Hi cerien, and welcome to the Linux community.

Can you able to post the output of

Code:

cat /var/log/messages

just after you try to connect?

cerien · 08-22-2013, 01:12 PM

Many thanks for the welcome & the help !

Here is the connection:

Code:

Aug 22 14:09:26 vps pptpd[7777]: CTRL: Client 93.121.xxx.yyy control connection started
Aug 22 14:09:26 vps pptpd[7777]: CTRL: Starting call (launching pppd, opening GRE)
Aug 22 14:09:26 vps pppd[7778]: pppd 2.4.4 started by root, uid 0
Aug 22 14:09:26 vps pppd[7778]: Using interface ppp0
Aug 22 14:09:26 vps pppd[7778]: Connect: ppp0 <--> /dev/pts/1
Aug 22 14:09:30 vps pptpd[7777]: CTRL: Ignored a SET LINK INFO packet with real ACCMs!
Aug 22 14:09:30 vps pppd[7778]: MPPE 128-bit stateless compression enabled
Aug 22 14:09:32 vps pppd[7778]: Cannot determine ethernet address for proxy ARP
Aug 22 14:09:32 vps pppd[7778]: local  IP address 172.16.36.1
Aug 22 14:09:32 vps pppd[7778]: remote IP address 172.16.36.10

And disconnection later ( when I disconnect the client intentionnally )

Code:

Aug 22 14:10:21 vps pppd[7778]: LCP terminated by peer (>^Z^WM-r^@<M-Mt^@^@^@^@)
Aug 22 14:10:21 vps pppd[7778]: Connect time 0.9 minutes.
Aug 22 14:10:21 vps pppd[7778]: Sent 15619 bytes, received 51354 bytes.
Aug 22 14:10:21 vps pppd[7778]: Modem hangup
Aug 22 14:10:21 vps pppd[7778]: Connection terminated.
Aug 22 14:10:21 vps pppd[7778]: Exit.
Aug 22 14:10:21 vps pptpd[7777]: CTRL: Client 93.121.xxx.yyy control connection finished

When I activate the DEBUG mode of PPTP, I can see data arriving from the client - but it gets lost in space (or somewhere else !)

Gad · 08-23-2013, 01:36 AM

Hi cerien,

I'm no expert but I have had my fair share of VPN setups.

Code:

Aug 22 14:09:32 vps pppd[7778]: Cannot determine ethernet address for proxy ARP

Are you running a DHCP server on the network? You may need to make sure your CentOS box is assigning IP addresses to the clients when they connect via VPN.

Also are you accessing this VPN over public network or is the VPN internal?

Best Regards
Marios

cerien · 08-23-2013, 07:43 AM

The Centos box is actually a VPS with ONE public IP assigned to it statically. It is accessed from a client behind a nat, through internet to this public IP. The client gets a correct IP adress in the range defined (172.16.36.x)

When I add noproxyarp in the options-pptpd, the message disappears - but no improvements.

Gad · 08-25-2013, 03:21 AM

Hi cerien,

As I've stated before that I am no "Guru" and was hoping that we would have more experienced input from the more wiser members.

The situation sounds a little tricky. You sound like you know your way with computers so Im sure you will agree that the problem could be almost anything.

There could be numerous factor that are affecting the VPN access.

If the packets are getting lost usually routers discard packets if the destination is not resolved. Have you tried adding the default gateway to your Local Area Connection advanced settings in the Windows 7 box trying to connect.

Are you running some sort of Firewall?

Also verify that you are able to connect from within the VPS network. This way you know that the VPN is indeed working and therefore eliminating the server at the same time.

cerien · 08-26-2013, 08:25 AM

Thanks - I have some knowledge indeed.... but I'm not a guru ;-)

I've looked at my client config when connecting to another vpn, and funny enough, I also get a gateway adress of 0.0.0.0 - but it works. This leads me to think that it is not a client configuration issue, but a server... Still searching in that direction !

Gad · 08-26-2013, 09:03 AM

Hi cerien,

If it helps, whenever i setup a VPN connection I test from the server first to ensure the connection does indeed work. Then I start working my way out.

cerien · 08-26-2013, 09:20 AM

I am not sure what you mean by "I test from the server first" - what sort of test do you carry out ? my server is connected to the internet and works fine - I think its the VPN config on its side which is incorrect