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GRE in Turkey
I have two VPS'es in Turkey, one with vps.systems and the other one with semele.com. I installed pptpd on both. When my client tried to connects to the pptpd, both returns GRE failed. I also have VPS'es in other countries without this problem. I'm wondering whether GRE is disabled in Turkey's network.
Comments
Turkey or Turnkey?
Either way, speak to your host. It sounds like your VPS does not have the GRE module enabled. Try "modprobe ip_gre" first.
The country Turkey. Sorry I spelled as Turnkey and I just corrected. Thanks for reminding.
Thanks. Tried
modprobe ip_gre
. It didn't complain anything and returned silence.I spoke to vps.systems, and they said they had nothing to restrict their network. Initially I thought the problem might be with my VPS, but now I have two VPS'es in the same countries. They appeared to have the same problem which doesn't exist in any other countries. I started to suspect whether there's anything to do with Turkey's network.
Ok, what does
lsmod | grep ip_gre
return?Sounds like it was enabled.
It return's nothing, like so:
Not
modprobe ip_gre
It's normal for it to return nothing, that means it's enabled.
What does
lsmod | grep ip_gre
return?That should show you if it enabled or not.
Sorry, my fault. It returns as follows:
I use exactly the same procedure to setup my servers. Could GRE be blocked by my provider's router instead of inside my VPS?
GRE traffic can be filtered at a network level, yes. But this does not explain the "GRE failed" error that your clients are seeing.
Try PPTP now that GRE is enabled on your Turkey VPS?
Sorry the client doesn't see "GRE failed". I apologize for the confusion. The GRE failed message actually is written into the log /var/log/syslog:
Just tried again, and the above is the same error message. The client received some connection disconnected message.
Try the connection while running this in a separate window or use screen:
tcpdump -ni any proto gre
If the packets are being filtered by your provider or their upstream, you won't see anything using the above command.
Thanks. I use my iPhone to connect. Here is the message from tcpdump while my phone is connecting: (x.x.x.x is the ip address of my phone, y.y.y.y is the ip address of the server.)
Are the following netfilter kernel modules enabled?
lsmod | grep nf_conntrack_pptp nf_conntrack_proto_gre
If not, enable using:
modprobe nf_conntrack_pptp nf_conntrack_proto_gre
Seems still no luck. The server OS is as follows:
Add the text
debug dump
to the /etc/ppp/options.pptpd or /etc/ppp/pptpd-options file. No need to restart pptpd.Then
tail -f /var/log/syslog
after the connection.I added
debug dump
to /etc/ppp/pptpd-options (/etc/ppp/options.pptpd doesn't exist in my system), and it worked. The client connected to the server without any problem. Then I removeddebug dump
and tried again, still worked without any problem. I have no idea how it magically worked. I'm pretty sure nothing is changed on my side before and after it suddenly worked.So I tried to connect to the other Turkish server, but it still doesn't work. Then I added
debug dump
to /etc/ppp/pptpd-options. Here is the output from tail -f /var/log/syslog:The first server worked for a few hours. But it doesn't work now. I didn't do anything in the server. I think it must be controlled by the network or router.