Hello, Reading http://www.shorewall.net/manpages/shorewall-masq.html i can see that the SOURCE parameter is required. Nevertheless i have some firewalls where i don't put the source address and the shorewall doesn't report any error: Example: root ~ # cat /etc/shorewall/masq eth0 eth2 ebckp:1.2.3.4 root ~ # shorewall check /dev/shm (...) Shorewall configuration verified root ~ # shorewall version 4.5.16.1 Which is correct? Thanks, Nuno Fernandes ------------------------------------------------------------------------------ HPCC Systems Open Source Big Data Platform from LexisNexis Risk Solutions Find What Matters Most in Your Big Data with HPCC Systems Open Source. Fast. Scalable. Simple. Ideal for Dirty Data. Leverages Graph Analysis for Fast Processing & Easy Data Exploration http://p.sf.net/sfu/hpccsystems