Ipmasq User's Manual - Dealing with Oddball Networks
An odball network is a network which fails to meet the assumptions
ipmasq makes (please see Assumptions, Section 2.3 for more
ipmasq incorrectly identify interfaces or misclassify
them (with respect to being internal or external), create a file
/etc/ipmasq/rules/A01interfaces.rul that defines the variables
EXTERNAL to contain the name of all your external interfaces (i.e.
EXTERNAL="eth0 eth0:0") and INTERNAL containing the names
of all interfaces connected to networks you wish to masquerade. Make
sure that the loopback interface (lo) appears in neither
EXTERNAL or INTERNAL.
ipmasq incorrectly determine the IP address, netmask,
or peer IP address of an interface, create a file
/etc/ipmasq/rules/A01precompute.rul that defines, for all
interfaces in EXTERNAL and INTERNAL, the IP address, netmask,
and peer IP address. (If you override the .def to change one
value, you must specify all values.) The following shows how to
define an interface foo0:
IPOFIF_foo0=10.1.2.3 NMOFIF_foo0=255.252.0.0 PEEROFIF_foo0=192.168.1.1
Aliased interfaces (i.e. foo0:0) are mangled before being made into variable names. The colon in the interface name is transformed into an underscore.