On 07/11/2012 12:22 AM, Eric Viseur wrote: > To ensure there are no interference with the monitor interface, I set > iptables to drop all the outbound traffic on eth1 and httpd in bound to the > IP address of eth0, but I randomly become unable to contact the webserver; ... > Any clues why this is happening ? Not off hand, but you could help by posting the configuration file containing your rules instead of a vague description of it. There's not really enough to go on yet. Rules dropping outbound traffic on the un-numbered interface are extraneous. If the kernel doesn't have an address on that interface, it won't have any routes assigned to that interface either. Hence, no traffic will be directed out of the un-numbered interface. If you list your rules with "iptables -L -v" you'll see the packet counter on that rule has 0 hits, because it's never used.