[vpn-help] Ubuntu / ShrewSoft VPN Client / tap0 = no packets

Christopher Piggott cpiggott at gmail.com
Sat Jul 14 10:30:13 CDT 2012


Hi,

I'm trying to troubleshoot a problem that I have seen mention of on
various mailing lists, but the only offered solution doesn't work for
me.  The client works fine on windows.  The linux version connects but
never passes traffic.  I am pretty familiar with tap/tun interfaces
and linux networking, so I don't think this is a n00b question.

After the tunnel is up, I see the tap0 interface created.
/sbin/ifconfig shows the interface with a valid address, and the
server (pfsense) shows me connected and having the same client
address.  My address is 10.111.20.2, and the network is
10.111.20.0/24.  The routing table looks great, with a host entry
toward tap0 and a route entry that matches the network address.

What never happens is packets.  To test all this I've been trying
connections, pinging, etc. but no packets ever go out tap0.  I know
this in two ways: first, ifconfig shows no activity on the counters.
Second, I started up wireshark and don't see any traffic to/from that
interface.

The things I have tried so far:

   * sysctl all rp_filter_* settings to 0 (no filtering
   * enable ip 'forwarding' on that interface (actually, on all
interfaces, as a test)
   * creating a bridge interface (br0) and bridging tap0 to eth0 (no help here)

The main thing that is puzzling me is why it's using tap0 instead of
tun0.  My understanding was the tap interfaces were userspace ethernet
adapters.  I would have expected it to use tun0 instead.

Any thoughts on this?  What would make it so that the tap0 interface
is configured and up, routes are set up correctly, yet no packets ever
actually get routed out that interface?  Or, am I being misled here
and wireshark and the counts aren't expected to work?

--Chris



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