VPN Help: PPTP on OpenVZ

Dean

Hi Guys,
I'm having some problems, and I could do with some advice please.
I'm currently using PPTP on OpenVZ which fires up OK - I get assigned IP address etc, and when I browse IPChicken.com it displays the Server's IP address instead of my residential ISP's one.

On my iPad etc, everything works hunky dory. I can browse the internet as normal through the VPN.
However, on a Windows machine (trying from two different computers) it's very fussy over what sites I can browse. Some will connect fine, others will just keep trying and trying and trying.

I've got ms-dns nameservers set (tried google ones and open-dns), and they get passed over to the windows computer. The computer also gets assigned an IP address.

Any pointers? It's happening on different boxes in different locations with different providers, but it specific to Windows client's connecting to them.

superpilesos

Try this
iptables -I FORWARD -p tcp --tcp-flags SYN,RST SYN -j TCPMSS --clamp-mss-to-pmtu

wlanboy

It could be DNS, this can be tested with nslookup tool to see the query time.
And for windows:
-> Network and Internet -> Network and Sharing Center -> Manage network connections -> select pptp connection -> right click ->Properties -> Networking -> deselect everthing you do not need.
Windows is sending out a ton of broadcasts once it connects to the network, if IPv6, File and Printer Sharing, etc is activated.

Dean

Unfortunately, neither made a difference

superpilesos

What are the results if you try to traceroute to a site that you're unable to connect to?

Dean

8 hops, and trace complete.

I don't get a connection error in the browser - it just keeps trying and trying and trying (and I may get a white page, or a part page).

If I visit the site not connected via VPN, and then visit it again after when i'm connected via VPN it seems to work fine for a little while.

nslookup is returning the correct results.

superpilesos

Well, you can try to change MTU on your computer
http://my.bergersoft.net/2010/05/13/how-to-change-mtu-size-on-windows-xpvista72008/

Dean

Set to 1400, no difference

mikho

lower it

http://secure.switchkonnect.com/knowledgebase/34/Frequent-disconnects-Unable-to-browse---PPTP-MTU-Issue---Windows.html

Dean

1350 seems to work... I read somewhere that if you have to change MTU, it means something's wrong somewhere? Is that the case?

Rallias

@DeanClinton said: I read somewhere that if you have to change MTU, it means something's wrong somewhere?

Are you using ipv4 or ipv6 to connect?

Dean

@Rallias - IPV4

Dean

Reduced MTU to 1300

mikho

Maximum Transmission Unit (MTU) in simple words is the maximum IP packet size in bytes, that can be transmitted over the underlying network. While most of time this never has to be changed from the default values there are instances when you need to alter the MTU sizes to fix certain network performance issues.