Homepage: http://www.shorewall.net/
Download: http://www.shorewall.de/pub/shorewall/
start
# Once you have configured Shorewall, you may change the setting of # this variable to 'Yes' # STARTUP_ENABLED=Yes
http://www.shorewall.net/Shorewall_and_Aliased_Interfaces.html
multihomed systems
# By setting DETECT_DNAT_IPADDRS=Yes, rules such as the above will apply # only if the original destination address is the primary IP address of # one of the interfaces associated with the source zone. Note that this # requires all interfaces to the source zone to be up when the firewall # is [re]started. # DETECT_DNAT_IPADDRS=No