/etc/shorewall/netmap
This file is used to map addresses in one network to corresponding addresses in a second network.
To use this file, your kernel and iptables must have NETMAP support included.
The columns in the file are as follows (where the column name is followed by a different name in parentheses, the different name is used in the alternate specification syntax).
TYPE - {DNAT|SNAT}[:{P|O|T}]
If DNAT or DNAT:P, traffic entering INTERFACE and addressed to NET1 has its destination address rewritten to the corresponding address in NET2.
If SNAT or SNAT:T, traffic leaving INTERFACE with a source address in NET1 has it's source address rewritten to the corresponding address in NET2.
If DNAT:O, traffic originating on the firewall and leaving via INTERFACE and addressed to NET1 has its destination address rewritten to the corresponding address in NET2.
If DNAT:P, traffic entering via INTERFACE and addressed to NET1 has its destination address rewritten to the corresponding address in NET2.
If SNAT:P, traffic entering via INTERFACE with a destination address in NET1 has it's source address rewritten to the corresponding address in NET2.
If SNAT:O, traffic originating on the firewall and leaving via INTERFACE with a source address in NET1 has it's source address rewritten to the corresponding address in NET2.
NET1 - network-address
INTERFACE - interface
NET2 - network-address
NET3 (Optional) - network-address
PROTO - protocol-number-or-name
DEST PORT(S) (dport) - port-number-or-name-list
If the protocol is ipp2p, this column is interpreted as an ipp2p option without the leading "--" (example bit for bit-torrent). If no PORT is given, ipp2p is assumed.
An entry in this field requires that the PROTO column specify icmp (1), tcp (6), udp (17), sctp (132) or udplite (136). Use '-' if any of the following field is supplied.
SOURCE PORT(S) (sport) - port-number-or-name-list
An entry in this field requires that the PROTO column specify tcp (6), udp (17), sctp (132) or udplite (136). Use '-' if any of the following fields is supplied.
/etc/shorewall/netmap
http://shorewall.net/netmap.html
http://shorewall.net/configuration_file_basics.htm#Pairs
shorewall(8), shorewall-accounting(5), shorewall-actions(5), shorewall-blacklist(5), shorewall-hosts(5), shorewall_interfaces(5), shorewall-ipsets(5), shorewall-maclist(5), shorewall-masq(5), shorewall-nat(5), shorewall-params(5), shorewall-policy(5), shorewall-providers(5), shorewall-proxyarp(5), shorewall-rtrules(5), shorewall-routestopped(5), shorewall-rules(5), shorewall.conf(5), shorewall-secmarks(5), shorewall-tcclasses(5), shorewall-tcdevices(5), shorewall-tcrules(5), shorewall-tos(5), shorewall-tunnels(5), shorewall-zones(5)