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internetsharing(8) [osx man page]

InternetSharing(8)					    BSD System Manager's Manual 					InternetSharing(8)

InternetSharing -- simple NAT/router configuration daemon SYNOPSIS
InternetSharing -d DESCRIPTION
InternetSharing is the back-end for the Internet Sharing feature. It is responsible for configuring the network interfaces, the DHCP server bootpd(8), the network address translation daemon natd(8), and the Internet domain name server named(8). named(8) is run in caching-only mode and allows the DHCP server to always offer the same DNS server address to the DHCP clients, regardless of the value of the actual DNS server addresses. The single command line option -d places additional debugging information to stdout/stderr. InternetSharing is launched by launchd(8) both at start-up and when the user turns Internet Sharing on in the Sharing preferences pane. By default, InternetSharing configures the IP addresses for non-AirPort interfaces starting at, walking up by one class C network (subnet mask for each subsequent interface i.e.,,, and so on. The AirPort interface by default is assigned CONFIGURATION
InternetSharing reads the property list stored in the /Library/Preferences/SystemConfiguration. Details of the are subject to change and are not completely documented here. The plist is a contract between the Sharing preferences pane and InternetSharing. Any details provided here are for informational purposes only. The plist is a dictionary with a single sub-dictionary called NAT containing properties to control which interfaces to use and other set- tings. It may also have a sub-dictionary called AirPort that is used to configure the AirPort interface when it is put into access point mode. One property worth mentioning is SharingNetworkNumberStart. This property controls the behavior of InternetSharing when it configures IP addresses for the local interfaces. The property is encoded as a string containing the dotted decimal network IP address, assumed to be a class C network. For example: <key>SharingNetworkNumberStart</key> <string></string> If the SharingNetworkNumberStart appears directly in the NAT dictionary, it controls the starting IP address chosen for the non-AirPort interfaces. If the property appears within the AirPort sub-dictionary, it controls the IP address assigned to the AirPort interface. The purpose of the property is to allow the user to avoid address collisions with existing NAT'd networks. SEE ALSO
bootpd(8), launchd(8), natd(8), named(8) Mac OS X Feburary 26, 2007 Mac OS X

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VLAN-INTERFACES(5)						   File formats 						VLAN-INTERFACES(5)

/etc/network/interfaces (vlan) - vlan extensions for the interfaces(5) file format DESCRIPTION
/etc/network/interfaces contains network interface configuration information for the ifup(8) and ifdown(8) commands. This manpage describes the vlan extensions to the standard interfaces(5) file format. Primary extensions exist to make and destroy vlan interfaces, secondary extensions exist for ipv4 interface manipulation which are gener- ally needed when using (a lot of) vlans. VLAN CREATION
Vlan interface definitions exist of the vlan interface name, and an optional 'raw-device' parameter. Vlan interfaces are numbered 1 to 4095. You have the option to have interface names zero-padded to 4 numbers, or just the plain digits without leading zero. The following example shows four ways to create a vlan with id 1 on interface eth0. They all result in different names. iface eth0.1 inet static address netmask iface vlan1 inet static vlan-raw-device eth0 address netmask iface eth0.0001 inet static address netmask iface vlan0001 inet static vlan-raw-device eth0 address netmask # We don't have br support out of the box iface br0.2 inet static vlan-raw-device br0 address netmask # Aliases are ignored iface br0.2:1 inet static address netmask EXTRA IFACE OPTIONS
Usually someone who uses vlans also wants to do some other manipulations with the ip stack or interface. vlan-raw-device devicename Indicates the device to create the vlan on. This is ignored when the devicename is part of the vlan interface name. ip-proxy-arp 0|1 Turn proxy-arp off or on for this specific interface. This also works on plain ethernet like devices. ip-rp-filter 0|1|2 Set the return path filter for this specific interface. This also works on plain ethernet like devices. hw-mac-address mac-address This sets the mac address of the interface before bringing it up. This works on any device that allows setting the hardware address with the ip command. AUTHOR
This manpage was adapted from interfaces(5) by Ard van Breemen <> SEE ALSO
vconfig(8) interfaces(5) vlan September 30 2007 VLAN-INTERFACES(5)
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