IPAliases.conf(5) BSD File Formats Manual IPAliases.conf(5)
NAME
IPAliases -- format of the IP aliases configuration file
DESCRIPTION
The file /etc/IPAliases.conf consists of newline separated ASCII records,
containing two or three colon-separated fields of the form
interface name of the interface
IP-addr the IP address to be associated with interface
netmask the optional netmask to be associated with IP-addr
The interface field is the name of network interface that will host the
IP alias. The interface field should consist of three or four charcters.
The interface must be "lo0" (implying the loopback interface), or an
interface returned by the ifconfig -l -u command. For example, the built-
in ethernet interface is typically named ``en0''.
The IP-addr field is the IP address to host on the indicated interface.
The IP-addr field must be a valid IP address in dotted-decimal notation.
For example, a valid IP address could be 10.0.100.253 or 196.221.43.3.
In Mac OS X Server 10.4 and later, CIDR notation is also supported. If
this notation is used, the netmask field must be not be present. Exam-
ples of valid CIDR notation include 10.0.100.253/16 and 196.221.43.3/24.
The netmask field is an optional field that defines the netmask associ-
ated with IP-addr. If this field is omitted and IP-addr does not specify
the mask via CIDR, the given IP-addr will use a default mask of
255.255.255.255 to avoid a common configuration problem: new addresses on
the same subnet as the first address assigned to interface must use this
``all ones'' format. (See the alias entry in ifconfig(8) for more
details.) The netmask field must be a valid mask in dotted-decimal nota-
tion, i.e. leading "one" bits followed by "zero" bits. For example,
192.0.0.0, 255.255.0.0, and 255.255.224.0 are "valid" netmasks, but
10.0.100.253 and 10.255.255.255 are not.
In addition to defining the configuration file, IP aliases must be
enabled in /etc/hostconfig by defining the IPALIASES record to "-YES-".
Addresses assigned to non-loopback interfaces are pinged by default to
determine their existence on the network. To eliminate this step and
force the acquisition of the addresses, define the PINGIPALIASES record
to "-NO-" in /etc/hostconfig.
Changes made to this file will not be activated until the next system
restart. To protect the system, a simple file permission and ownership
check is performed before loading the configuration file: the file is
only loaded if it is owned by root and is not writeable by group or
other. See chmod(2) for an explanation of file modes and how to change
them.
EXAMPLES
A valid configuration file might contain
lo0:10.254.0.10/16
lo0:10.254.0.11/16
en0:10.254.0.91
en1:10.254.0.206
en2:10.254.0.101:255.255.0.0
en2:10.254.0.191:255.255.0.0
FILES & FOLDERS
/usr/libexec/IPAliases
/etc/IPAliases.conf
/etc/hostconfig
/var/log/IPAliases.log
SEE ALSO
ifconfig(8), ping(8)
Mac OS X Server September 4, 2008 Mac OS X Server
Mac OS X 10.6Server - Generated Thu Apr 15 07:12:10 CDT 2010