HardenedBSD/sbin/ifconfig/ifconfig.8

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.\"     From: @(#)ifconfig.8	8.3 (Berkeley) 1/5/94
.\" $FreeBSD$
.\"
.Dd February 13, 1996
.Dt IFCONFIG 8
.Os BSD 4.2
.Sh NAME
.Nm ifconfig
.Nd configure network interface parameters
.Sh SYNOPSIS
.Nm ifconfig
.Ar interface address_family
.Oo
.Ar address
.Op Ar dest_address
.Oc
.Op Ar parameters
.Nm ifconfig
.Fl a
.Op Fl d
.Op Fl u
.Op Ar address_family
.Nm ifconfig
.Fl l
.Op Fl d
.Op Fl u
.Op Ar address_family 
.Sh DESCRIPTION
.Nm Ifconfig
is used to assign an address
to a network interface and/or configure
network interface parameters.
.Nm Ifconfig
must be used at boot time to define the network address
of each interface present on a machine; it may also be used at
a later time to redefine an interface's address
or other operating parameters.
.Pp
The following options are available:
.Bl -tag -width indent
.It Ar address
For the
.Tn DARPA Ns -Internet
family,
the address is either a host name present in the host name data
base, 
.Xr hosts 5 ,
or a
.Tn DARPA
Internet address expressed in the Internet standard
.Dq dot notation .
.\" For the Xerox Network Systems(tm) family,
.\" addresses are 
.\" .Ar net:a.b.c.d.e.f ,
.\" where
.\" .Ar net
.\" is the assigned network number (in decimal),
.\" and each of the six bytes of the host number,
.\" .Ar a
.\" through
.\" .Ar f ,
.\" are specified in hexadecimal.
.\" The host number may be omitted on 10Mb/s Ethernet interfaces,
.\" which use the hardware physical address,
.\" and on interfaces other than the first.
.\" For the
.\" .Tn ISO
.\" family, addresses are specified as a long hexadecimal string,
.\" as in the Xerox family.  However, two consecutive dots imply a zero
.\" byte, and the dots are optional, if the user wishes to (carefully)
.\" count out long strings of digits in network byte order.
.It Ar address_family
Specify the
.Ar "address family"
which affects interpretation of the remaining parameters.
Since an interface can receive transmissions in differing protocols
with different naming schemes, specifying the address family is recommended.
The address or protocol families currently
supported are
.Dq inet ,
.Dq inet6 ,
.Dq atalk ,
.\" .Dq iso ,
and
.Dq ipx .
.\" and
.\" .Dq ns .
.It Ar dest_address
Specify the address of the correspondent on the other end
of a point to point link.
.It Ar interface
This
parameter is a string of the form
.Dq name unit ,
for example,
.Dq en0 .
.El
.Pp
The following parameters may be set with 
.Nm ifconfig :
.Bl -tag -width indent
.It Cm add
Another name for the ``alias'' parameter.  Introduced for compatibility
with BSD/OS.
.It Cm alias
Establish an additional network address for this interface.
This is sometimes useful when changing network numbers, and
one wishes to accept packets addressed to the old interface.
If the address is on the same subnet as the first network address
for this interface, a netmask of 0xffffffff has to be specified.
.It Fl alias
Remove the network address specified.
This would be used if you incorrectly specified an alias, or it
was no longer needed.
If you have incorrectly set an NS address having the side effect
of specifying the host portion, removing all NS addresses will
allow you to respecify the host portion.
.It Cm anycast
(Inet6 only)
Specify that the address configured is an anycast address.
Based on the current specification,
only routers may configure anycast addresses.
Anycast address will not be used as source address of any of outgoing
IPv6 packets.
.It Cm arp
Enable the use of the Address Resolution Protocol in mapping
between network level addresses and link level addresses (default).
This is currently implemented for mapping between
.Tn DARPA
Internet
addresses and 10Mb/s Ethernet addresses.
.It Fl arp
Disable the use of the Address Resolution Protocol.
.It Cm broadcast
(Inet only)
Specify the address to use to represent broadcasts to the
network.
The default broadcast address is the address with a host part of all 1's.
.It Cm debug
Enable driver dependent debugging code; usually, this turns on
extra console error logging.
.It Fl debug
Disable driver dependent debugging code.
.It Cm delete
Another name for the ``-alias'' parameter.
.It Cm down
Mark an interface ``down''.  When an interface is
marked ``down'', the system will not attempt to
transmit messages through that interface. 
If possible, the interface will be reset to disable reception as well.
This action does not automatically disable routes using the interface.
.\" .It Cm ipdst
.\" This is used to specify an Internet host who is willing to receive
.\" ip packets encapsulating NS packets bound for a remote network.
.\" An apparent point to point link is constructed, and
.\" the address specified will be taken as the NS address and network
.\" of the destination.
.\" IP encapsulation of
.\" .Tn CLNP
.\" packets is done differently.
.It Cm lladdr Ar addr
Set the link-level address on an interface. This can be used to
e.g. set a new MAC address on an ethernet interface, though the
mechanism used is not ethernet-specific. The address
.Ar addr
is specified as a series of colon-separated hex digits.
If the interface is already
up when this option is used, it will be briefly brought down and
then brought back up again in order to insure that the receive
filter in the underlying ethernet hardware is properly reprogrammed.
.It Cm media Ar type
If the driver supports the media selection system, set the media type
of the interface to
.Ar type .
Some interfaces support the mutually exclusive use of one of several
different physical media connectors.  For example, a 10Mb/s Ethernet
interface might support the use of either
.Tn AUI
or twisted pair connectors.  Setting the media type to
.Dq 10base5/AUI
would change the currently active connector to the AUI port.
Setting it to
.Dq 10baseT/UTP
would activate twisted pair.  Refer to the interfaces' driver
specific documentation or man page for a complete list of the
available types.
.It Cm mediaopt Ar opts
If the driver supports the media selection system, set the specified
media options on the interface.
.Ar Opts
is a comma delimited list of options to apply to the interface.
Refer to the interfaces' driver specific man page for a complete
list of available options.
.It Fl mediaopt Ar opts
If the driver supports the media selection system, disable the
specified media options on the interface.
.It Cm vlan Ar vlan_tag
If the interface is a vlan pseudo interface, set the vlan tag value
to
.Ar vlan_tag .
This value is a 16-bit number which is used to create an 802.1Q
vlan header for packets sent from the vlan interface.
Note that
.Cm vlan
and
.Cm vlandev
must both be set at the same time.
.It Cm vlandev Ar iface
If the interface is a vlan pseudo device, associate physical interface
.Ar iface
with it.
Packets transmitted through the vlan interface will be
diverted to the specified physical interface
.Ar iface
with 802.1Q vlan encapsulation.
Packets with 802.1Q encapsulation received
by the parent interface with the correct vlan tag will be diverted to
the associated vlan pseudo-interface.
The vlan interface is assigned a
copy of the parent interface's flags and the parent's ethernet address.
The
.Cm vlandev
and
.Cm vlan
must both be set at the same time.
If the vlan interface already has
a physical interface associated with it, this command will fail.
To
change the association to another physical interface, the existing
association must be cleared first.
.Pp
Note: if the
.Ar link0
flag is set on the vlan interface, the vlan pseudo
interface's behavior changes: the
.Ar link0
tells the vlan interface that the
parent interface supports insertion and extraction of vlan tags on its
own (usually in firmware) and that it should pass packets to and from
the parent unaltered.
.It Fl vlandev Ar iface
If the driver is a vlan pseudo device, disassociate the physical interface
.Ar iface
from it.
This breaks the link between the vlan interface and its parent,
clears its vlan tag, flags and its link address and shuts the interface down.
.It Cm metric Ar n
Set the routing metric of the interface to
.Ar n ,
default 0.
The routing metric is used by the routing protocol
.Pq Xr routed 8 .
Higher metrics have the effect of making a route
less favorable; metrics are counted as addition hops
to the destination network or host.
.It Cm mtu Ar n
Set the maximum transmission unit of the interface to
.Ar n ,
default is interface specific.
The mtu is used to limit the size of packets that are transmitted on an
interface.
Not all interfaces support setting the mtu, and some interfaces have
range restrictions.
.It Cm netmask Ar mask
.\" (Inet and ISO)
(Inet only)
Specify how much of the address to reserve for subdividing
networks into sub-networks.
The mask includes the network part of the local address
and the subnet part, which is taken from the host field of the address.
The mask can be specified as a single hexadecimal number
with a leading 0x, with a dot-notation Internet address,
or with a pseudo-network name listed in the network table
.Xr networks 5 .
The mask contains 1's for the bit positions in the 32-bit address
which are to be used for the network and subnet parts,
and 0's for the host part.
The mask should contain at least the standard network portion,
and the subnet field should be contiguous with the network
portion.
.It Cm prefixlen Ar len
(Inet6 only)
Specify that
.Ar len
bits are reserved for subdividing networks into sub-networks.
The
.Ar len
must be integer, and for syntactical reason it must be between 0 to 128.
It is almost always 64 under the current IPv6 assignment rule.
If the parameter is ommitted, 64 is used.
.\" see 
.\" Xr eon 5 .
.\" .It Cm nsellength Ar n
.\" .Pf ( Tn ISO
.\" only)
.\" This specifies a trailing number of bytes for a received
.\" .Tn NSAP
.\" used for local identification, the remaining leading part of which is
.\" taken to be the
.\" .Tn NET
.\" (Network Entity Title).
.\" The default value is 1, which is conformant to US
.\" .Tn GOSIP .
.\" When an ISO address is set in an ifconfig command,
.\" it is really the
.\" .Tn NSAP
.\" which is being specified.
.\" For example, in
.\" .Tn US GOSIP ,
.\" 20 hex digits should be
.\" specified in the
.\" .Tn ISO NSAP
.\" to be assigned to the interface.
.\" There is some evidence that a number different from 1 may be useful
.\" for
.\" .Tn AFI
.\" 37 type addresses.
.It Cm range
Under appletalk, set the interface to respond to a 
.Em netrange.
of the form startnet-endnet.
Appletalk uses this scheme instead of 
netmasks though
.Fx
implements it internally as a set of netmasks.
.It Cm remove
Another name for the ``-alias'' parameter.  Introduced for compatibility
with BSD/OS.
.It Cm phase
The argument following this specifies the version (phase) of the 
Appletalk network attached to the interface.
Values of 1 or 2 are permitted.
.It Cm link[0-2]
Enable special processing of the link level of the interface.
These three options are interface specific in actual effect, however,
they are in general used to select special modes of operation.
An example
of this is to enable SLIP compression, or to select the connector type
for some Ethernet cards.  Refer to the man page for the specific driver
for more information.
.It Fl link[0-2]
Disable special processing at the link level with the specified interface.
.It Cm up
Mark an interface
.Dq up . 
This may be used to enable an interface after an
.Dq ifconfig down .
It happens automatically when setting the first address on an interface.
If the interface was reset when previously marked down,
the hardware will be re-initialized.
.El
.Pp
.Nm Ifconfig
displays the current configuration for a network interface
when no optional parameters are supplied.
If a protocol family is specified,
.Nm
will report only the details specific to that protocol family.
.Pp
If the driver does supports the media selection system, the supported
media list will be included in the output.
.Pp
If
.Fl L
flag is supplied, address lifetime is dislayed for IPv6 addresses,
as time offset string.
.Pp
Optionally, the
.Fl a
flag may be used instead of an interface name.  This flag instructs
.Nm
to display information about all interfaces in the system.
The
.Fl d
flag limits this to interfaces that are down, and
.Fl u
limits this to interfaces that are up.
.Pp
The
.Fl l
flag may be used to list all available interfaces on the system, with
no other additional information.  Use of this flag is mutually exclusive
with all other flags and commands, except for
.Fl d
(only list interfaces that are down)
and
.Fl u 
(only list interfaces that are up).
.Pp
Only the super-user may modify the configuration of a network interface.
.Sh NOTES
The media selection system is relatively new and only some drivers support
it (or have need for it).
.Sh DIAGNOSTICS
Messages indicating the specified interface does not exist, the
requested address is unknown, or the user is not privileged and
tried to alter an interface's configuration.
.Sh BUGS
IPv6 link-local addresses are required for several basic communication
between IPv6 node.
If they are deleted by
.Nm ifconfig
manually, the kernel might show very strange behavior.
So, such manual deletions are strongly discouraged.
.Sh SEE ALSO
.Xr netstat 1 ,
.Xr netintro 4 ,
.Xr rc 8 ,
.Xr routed 8
.\" .Xr eon 5
.Sh HISTORY
The
.Nm
command appeared in
.Bx 4.2 .