Greetings to all,
I'm experiencing some problems while trying to connect to a PPTP VPN server.
Here's the scenario:
Clients ------->------- WRT54GL router ------->------- PPTP VPN Server
172.16.0.0/24 172.16.0.1 66.150.105.18
The Linksys WRT54GL router is running a custom firmware (DD-WRT v24 [1]) which
is essentially Linux (dmesg attached) with netfilter and iptables (not sure
which iptables version, but it's 1.2.9 or later). The WAN connection is DHCP
cable modem.
# uname -a
Linux gateway 2.4.34 #753 Thu Feb 15 16:56:46 CET 2007 mips unknown
The router has PPTP VPN passthrough enabled which, in essence, loads the
ip_nat_pptp, ip_conntrack_pptp, ip_conntrack_proto_gre and ip_nat_proto_gre
modules and adds these two rules to the FORWARD chain (full iptables output
also attached):
ACCEPT gre -- 172.16.0.0/24 anywhere
ACCEPT tcp -- 172.16.0.0/24 anywhere tcp dpt:1723
So far, so good, I'm able to connect to the VPN and everything is ok. The
problem is, whenever I start a network intensive application (such as the
bittorrent client Azureus [2]), the connection dies after a couple of minutes.
By "dead" I mean no more traffic, though the VPN remains connected (not "hung
up"). I can still ping the VPN gateway, but that's all I can do. I need to
manually disconnect and reconnect in order to use the VPN resources again.
When I lose VPN connectivity, the router's log get flooded by these messages:
Feb 26 01:59:16 gateway user.warn kernel: unknown GRE version 5
Feb 26 01:59:16 gateway user.warn kernel: unknown GRE version 5
Feb 26 01:59:16 gateway user.warn kernel: unknown GRE version 5
Feb 26 01:59:16 gateway user.warn kernel: unknown GRE version 5
Feb 26 01:59:16 gateway user.warn kernel: unknown GRE version 5
Feb 26 01:59:16 gateway user.warn kernel: unknown GRE version 5
Feb 26 01:59:16 gateway user.warn kernel: unknown GRE version 5
Feb 26 01:59:17 gateway user.warn kernel: unknown GRE version 5
Feb 26 01:59:17 gateway user.warn kernel: unknown GRE version 5
I do get a quick burst of the above messsages even when I still have
connectivity. This quick burst usually happens once or twice, but short
after, the connectivity is gone.
Just doing low traffic stuff such as web browsing does not yield any issues
and I stay connected normally.
Now the bad part: if I remove the router and connect the cable modem directly
to the computer, I get zero problems. So, it looks like the problem lies on
the router.
Does anyone know what these "unknown GRE version 5" mean? Some have said the
router doesn't seem to support GRE version 5, but how can I be sure of that?
I also asked for help in two places: in the VPN forum [3] and in the DD-WRT
forum [4]. There's also another thread on another forum [5], where other
WRT54G users have the same issue, though on different firmware (Tomato, but
still Linux). You may look at those threads for further reference of this
issue.
Any help is greatly welcomed.
Thanks
Gustavo
[1] http://www.dd-wrt.com
[2] http://azureus.sourceforge.net
[3] http://www.secureix.com/phpBB2/viewtopic.php?p=453
[4] http://www.dd-wrt.com/phpBB2/viewtopic.php?t=11641
[5] http://www.linksysinfo.org/forums/showthread.php?t=51331
[6] http://www.polarcloud.com/tomato
dmesg.txt
Description: Text document
iptables.txt
Description: Text document
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