hello,

i am trying to set up a gre tunnel on my kimsufi server. Unfortunately their stock kernel did not support it, so i installed my own kernel. what ive done is install the stock debian 7 kernel with apt, then use the config to compile my own 3.2.68 grsec kernel.

i have a vps that was being used to tunnel to an ubuntu 14 server w/ grsec at volumedrive, and everything worked fine.

i have followed the basic steps of:

iptunnel add gre1 mode gre local 198.245.51.x remote 185.62.188.x ttl 255
ip addr add 192.168.120.2/30 dev gre1
ip link set gre1 up


the tunnel shows up on the vps, with ifconfig showing data being sent.
on the kimsufi ifconfig shows no data sent or received, just the interface.

i have searched and searched and have not found anything on this. i have turned off all iptables rules as well. i tried on the stock kernel, vanilla 3.2.68 kernel, grsec kernel and its the same. I initially thought it was the kernel, but i no longer think so.

any insight? maybe some crazy setting is set thats blocking gre?

this is a fresh debian 7 with ispconfig 3.0.5.4p5 (from kimsufi/ovh's image)

so i found out this is not related just to gre, but ipv6 as well and probably any other tunnel.

you can see in both interfaces that no data is sent or recieved.



eth0 Link encap:Ethernet HWaddr 00:1e:8c:f1:90:a8
inet addr:198.245.51.x Bcast:198.245.51.255 Mask:255.255.255.0
inet6 addr: 2607:5300:60:61c::1/128 Scope:Global
inet6 addr: fe80::21e:8cff:fef1:90a8/64 Scope:Link
UP BROADCAST RUNNING MULTICAST MTU:1450 Metric:1
RX packets:1495 errors:0 dropped:0 overruns:0 frame:0
TX packets:2358 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:196163 (191.5 KiB) TX bytes:360598 (352.1 KiB)
Interrupt:20 Memory:fe500000-fe520000

gre1 Link encap:UNSPEC HWaddr C6-F5-33-1C-00-00-00-00-00-00-00-00-00-00-00-00
inet addr:192.168.120.2 P-t-P:192.168.120.2 Mask:255.255.255.252
inet6 addr: fe80::200:5efe:c6f5:331c/64 Scope:Link
UP POINTOPOINT RUNNING NOARP MTU:1476 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

he-ipv6 Link encap:IPv6-in-IPv4
inet6 addr: fe80::c6f5:331c/128 Scope:Link
inet6 addr: 2001:470:x:xxx::2/64 Scope:Global
UP POINTOPOINT RUNNING NOARP MTU:1480 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:0 (0.0 B) TX bytes:0 (0.0 B)

I solved this issue.

ovh/kimsufi set several sysctl entries in /etc/sysctl.conf in all of their linux distributions.

by commenting out everything below "disable ipv6 autoconf" it will solve this issue, however their stock kernel foes not support gre. You will still have to either install a stock kernel or vanilla kernel. You will need a config file as well since they do not include one in /boot. you can find them at ftp.ovh.net in /made-in-ovh/bzImage

hope this helps someone in the future!