From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jan Ceuleers Subject: Why might packets go into a tunnel and not come out Date: Sun, 02 Oct 2011 11:25:04 +0200 Message-ID: <4E882DF0.90404@computer.org> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit To: netdev@vger.kernel.org Return-path: Received: from mailrelay007.isp.belgacom.be ([195.238.6.173]:62104 "EHLO mailrelay007.isp.belgacom.be" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751456Ab1JBJ2S (ORCPT ); Sun, 2 Oct 2011 05:28:18 -0400 Received: from [192.168.1.6] (wendy.xperim.be [192.168.1.6]) by zotac.xperim.be (8.14.3/8.14.3/Debian-9.2ubuntu1) with ESMTP id p929P4hg000695 for ; Sun, 2 Oct 2011 11:25:07 +0200 Sender: netdev-owner@vger.kernel.org List-ID: All, This is a question that I would have posted to linux-net had it still existed. I beg your indulgence. I have established an SSH tunnel (device tunX) between two remote hosts. This tunnel is operating properly in that I can ping each peer from the other. I am now trying to route traffic through this tunnel to onward destinations. This is not working: when I ping such an onward destination I can see the packets going into the tunnel (using tcpdump) but they're not coming out of the other end (again as seen by tcpdump). I have added logging to all firewall rules that drop or reject traffic; nothing is logged. (And yes I have checked that logging itself works by briefly adding logging to an ACCEPT rule). Routing is enabled on both hosts. The counters for the tun devices (as seen using ifconfig) do not show any dropped traffic. I am not asking you to debug my problem for me, but could anyone please point me to an overview of the reasons why packets might be going into one end of a tunnel and not come out the other end? I have studied the diagram at the following link and I think I've checked the potential issues that it prompts: http://www.shorewall.net/Shorewall_and_Routing.html Many thanks. Jan