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DHCPD, Multiple interfaces, Single Subnet
10-26-2005
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ifup(8) ifup(8) NAME
ifup - bring a network interface up ifdown - take a network interface down SYNOPSIS
ifup [-nv] [--no-act] [--verbose] [-i FILE|--interfaces=FILE] [--allow CLASS] -a|IFACE... ifup -h|--help ifup -V|--version ifdown [-nv] [--no-act] [--verbose] [-i FILE|--interfaces=FILE] [--allow CLASS] -a|IFACE... DESCRIPTION
The ifup and ifdown commands may be used to configure (or, respectively, deconfigure) network interfaces based on interface definitions in the file /etc/network/interfaces. OPTIONS
A summary of options is included below. -a, --all If given to ifup, affect all interfaces marked auto. Interfaces are brought up in the order in which they are defined in /etc/net- work/interfaces. If given to ifdown, affect all defined interfaces. Interfaces are brought down in the order in which they are currently listed in the state file. Only interfaces defined in /etc/network/interfaces will be brought down. --force Force configuration or deconfiguration of the interface. -h, --help Show summary of options. --allow=CLASS Only allow interfaces listed in an allow-CLASS line in /etc/network/interfaces to be acted upon. -i FILE, --interfaces=FILE Read interface definitions from FILE instead of from /etc/network/interfaces. -e PATTERN, --exclude=PATTERN Exclude interfaces from the list of interfaces to operate on by the PATTERN. Notice that the PATTERN can be a full interface name or substrings that match interfaces. Users could easily have unexpected behaviour if they use a small string to do the match. -n, --no-act Don't configure any interfaces or run any "up" or "down" commands. --no-mappings Don't run any mappings. See interfaces(5) for more information about the mapping feature. -V, --version Show copyright and version information. -v, --verbose Show commands as they are executed. EXAMPLES
ifup -a Bring up all the interfaces defined with auto in /etc/network/interfaces ifup eth0 Bring up interface eth0 ifup eth0=home Bring up interface eth0 as logical interface home ifdown -a Bring down all interfaces that are currently up. NOTES
ifup and ifdown are actually the same program called by different names. The program does not configure network interfaces directly; it runs low level utilities such as ip to do its dirty work. FILES
/etc/network/interfaces definitions of network interfaces See interfaces(5) for more information. /var/run/network/ifstate current state of network interfaces KNOWN BUGS
/LIMITATIONS The program keeps records of whether network interfaces are up or down. Under exceptional circumstances these records can become inconsis- tent with the real states of the interfaces. For example, an interface that was brought up using ifup and later deconfigured using ifcon- fig will still be recorded as up. To fix this you can use the --force option to force ifup or ifdown to run configuration or deconfigura- tion commands despite what it considers the current state of the interface to be. The file /var/run/network/ifstate must be writable for ifup or ifdown to work properly. On Ubuntu the /var/run location is a temporary filesystem which is always writable and thrown away on shutdown. You can also use the --force option to run configuration or deconfigura- tion commands without updating the file. Note that the program does not run automatically: ifup alone does not bring up interfaces that appear as a result of hardware being installed and ifdown alone does not bring down interfaces that disappear as a result of hardware being removed. To automate the configura- tion of network interfaces you need to install other packages such as hotplug(8) or ifplugd(8). AUTHOR
The ifupdown suite was written by Anthony Towns <aj@azure.humbug.org.au>. SEE ALSO
interfaces(5), ip(8), ifconfig(8). IFUPDOWN
22 May 2004 ifup(8)