ifconfig(1M) ifconfig(1M)
NAME [Toc] [Back]
ifconfig - configure network interface parameters
SYNOPSIS [Toc] [Back]
ifconfig interface [address_family] [address [dest_address]]
[parameters]
ifconfig interface [address_family]
DESCRIPTION [Toc] [Back]
The first form of the ifconfig command assigns an address to a network
interface and/or configures network interface parameters. ifconfig
must be used at boot time to define the network address of each
interface present on a machine. It can also be used at other times to
redefine an interface's address or other operating parameters. If the
address_family is not specified, the address family defaults to IPv4.
The second form of the command, without address_family, displays the
current configuration for interface. If address_family is not
specified, ifconfig reports the details on all supported address
families. An exception is when the user has not configured any
interface with an IPv6 address, ifconfig does not display the IPv6
loopback interface.
Only a user with appropriate privileges can modify the configuration
of a network interface. All users can run the second form of the
command.
Arguments [Toc] [Back]
ifconfig recognizes the following arguments:
address Either a host name present in the host name
database (see hosts(4)), or a DARPA Internet
address expressed in Internet standard dot
notation (see inet(3N)) for an IPv4 address and
in colon notation (see inet6(3N)) for an IPv6
address.
address_family Name of protocol on which naming scheme is based.
An interface can receive transmissions in
differing protocols, each of which may require
separate naming schemes. The address_family,
affects the interpretation of the remaining
parameters on the command line. The only address
families currently supported are inet (DARPAInternet
family) for IPv4 addresses, and inet6
for IPv6 addresses.
dest_address Address of destination system. Consists of
either a host name present in the host name
database (see hosts(4)), or a DARPA Internet
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address expressed in Internet standard dot
notation (see inet(3N)) for an IPv4 address, and
in colon notation (see inet6(3N)) for an IPv6
address.
interface A string of the form nameunit, such as lan0.
(See the Interface Naming subsection given
below.)
parameters One or more of the following operating
parameters:
up Mark an interface "up". Enables
interface after an ifconfig down.
Occurs automatically when setting
the address on an interface.
Setting this flag has no effect if
the hardware is "down". A
secondary interface (see the
Interface Naming subsection given
below) can be marked up only if
the primary interface is already
up.
down Mark an interface "down". When an
interface is marked "down", the
system will not attempt to
transmit messages through that
interface. A primary interface
(see the Interface Naming
subsection given below) can be
marked down only if all the
secondary interfaces on the same
physical device are already down.
broadcast (inet only) Specify the address
that represents broadcasts to the
network. The default broadcast
address is the address with a host
part of all 1's.
encaplimit n Specify the tunnel encapsulation
limit value n. The tunnel
encapsulation limit is the maximum
number of additional
encapsulations permitted for the
packets. The tunnel encapsulation
limit option is defined in RFC
2473. This option is valid only
for tunnel types ipinip6 and
ip6inip6. The default is 4.
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forward (inet6 only) Enable forwarding of
packets by this interface. This
is the default behavior.
-forward (inet6 only) Disable forwarding of
packets by this interface.
metric n Set the routing metric of the
interface to n. The default is 0.
The routing metric is used by the
routing protocol (see gated(1M)).
Higher metrics have the effect of
making a route less favorable;
metrics are counted as additional
hops to the destination network or
host.
netmask mask (inet only) Specify how much of
the address to reserve for
subdividing networks into subnetworks
or aggregating networks
into supernets. 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 (see
networks(4)). For subdividing
networks into sub-networks, mask
must include the network part of
the local address, and the subnet
part which is taken from the host
field of the address. mask must
contain 1's in the bit positions
in the 32-bit address that are to
be used for the network and subnet
parts, and 0's in the host part.
The 1's in the mask must be
contiguous starting from the
leftmost bit position in the 32-
bit field. mask must contain at
least the standard network
portion, and the subnet field must
be contiguous with the network
portion. The subnet field must
contain at least 1 bit. For
aggregating networks into
supernets, mask must only include
a portion of the network part.
mask must contain contiguous 1's
in the bit positions starting from
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the leftmost bit of the 32-bit
field.
prefix n (inet6 only) n indicates the
length of the network prefix
associated with this interface.
The primary interface (see
Interface Naming subsection given
below) prefix length is always 10,
and is not configurable. The
prefix option can be used only
with the address option, and only
for secondary interfaces.
Default: 64. Range: 1 to 128.
private (inet6 only) Enable processing of
received router advertisements.
Secondary address(es) will be
autoconfigured on the interface
using the prefix(es) received in
router advertisement(s). This is
the default behavior.
-private (inet6 only) Disable processing of
received router advertisements.
tunnel type Specify the type of tunnel. The
tunnel types can be ip6inip,
ipinip6, ip6inip6, and 6to4.
tdst addr Specify the destination addr of
the tunnel. This is the
destination address in the
encapsulating (outer) header. It
should be an address configured on
an interface on the tunnel exitpoint
node. For tunnel types
ipinip6 and ip6inip6, the addr
should be an IPv6 address. For
tunnel type ip6inip, the addr
should be an IPv4 address; and for
tunnel type 6to4, the tdst
parameter should not be specified.
tsrc addr Specify the source addr of the
tunnel. This is the source
address in the encapsulating
(outer) header. It should be an
address configured on an interface
in the tunnel entry-point node.
For tunnel types ipinip6 and
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ip6inip6, the addr should be an
IPv6 address. For tunnel types
ip6inip and 6to4, the addr should
be an IPv4 address.
arp (inet only) Enable the user of the
Address Resolution Protocol in
mapping between network level
addresses and link level addresses
(default). If an interface
already had the Address Resolution
Protocol disabled, the user must
"unplumb" the interface before it
can be enabled for Address
Resolution Protocol.
-arp (inet only) Disable the use of the
Address Resolution Protocol. If
an interface already had the
Address Resolution Protocol
enabled, the user must "unplumb"
the interface before it can be
disabled for Address Resolution
Protocol.
plumb Setup the Streams plumbing needed
for TCP/IP for a primary interface
name. (See the Interface Naming
subsection given below.). By
default, the plumb operation is
done automatically when an IP
address is specified for an
interface.
unplumb Tear down the Streams plumbing for
a primary interface name. (See
the Interface Naming subsection
given below.) Secondary interface
does not require "plumbing". A
secondary IPv4 interface can be
removed by assigning an IP address
of 0.0.0.0 to it. Remove a
secondary IPv6 interface by
assigning an IP address of :: to
it.
Interface Naming [Toc] [Back]
The interface name associated with a network card is composed of the
name of the interface (e.g. lan or snap ), the ppa number which
identifies the card instance for this interface, and an optional IP
index number which allows the configuration of multiple IP addresses
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for an interface. For LAN cards, the interface name lan will be used
to designate Ethernet encapsulation and snap for IEEE 802.3
encapsulation. The lanscan command can be used to display the
interface name and ppa number of each interface that is associated
with a network card (see lanscan(1M)).
IPv4 and IPv6 interfaces can coexist over the same physical network
interface device using the same naming scheme. IPv6 interfaces are
configured using the "inet6" ifconfig subcommand. (See the IPv6
subsection given below.)
The tunnel interface names should be iptu* for "IP6-in-IP" tunnels and
6to4 tunnels. Example: iptu0, iptu1. The tunnel interface names
should be ip6tu* for "IP-in-IP6" tunnels and "IP6-in-IP6" tunnels.
Example: ip6tu0, ip6tu1.
IP Index Number [Toc] [Back]
Multiple IP addresses assigned to the same interface may be in
different subnets. An example of an interface name without an IP
index number is lan0. An example of an interface name with a IP index
number is lan0:1. Note: specifying lan0:0 is equivalent to lan0.
A primary interface is an interface whose IP index number is zero. A
secondary interface is an interface whose IP index number is non-zero.
Loopback Interface [Toc] [Back]
The loopback interface (lo0) is automatically configured when the
system boots with the TCP/IP software. The IP address and netmask of
the primary IPv4 loopback interface are 127.0.0.1 and 255.0.0.0,
respectively. The IP address and prefix of the primary IPv6 loopback
interface are ::1 and 128 respectively. The user is not permitted to
change the address of the primary loopback interface (lo0:0). It is
permissible to assign other IP addresses to lo0 with non-zero IP index
numbers (lo0:1, lo0:2, etc). This allows a system to have a "system
IP" address that is available as long as one interface remains usable.
Supernets [Toc] [Back]
(inet only) A supernet is a collection of smaller networks.
Supernetting is a technique of using the netmask to aggregate a
collection of smaller networks into a supernet.
This technique is particularly useful when the limit of 254 hosts per
class C network is too restrictive. In those situations a netmask
containing only a portion of the network part may be applied to the
hosts in these networks to form a supernet. This supernet netmask
should be applied to those interfaces that connect to the supernet
using the ifconfig command. For example, a host can configure its
interface to connect to a class C supernet, 192.6, by configuring an
IP address of 192.6.1.1 and a netmask of 255.255.0.0 to its interface.
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IPv6 Interfaces [Toc] [Back]
inet6 must be specified when an IPv6 interface is configured. The
address for an IPv6 interface can either be a hostname present in the
host name database (see hosts(4)), or an address in the IPv6 colon
notation.
Stateless Address Auto-configuration:
Unlike IPv4 interfaces, IPv6 interfaces can be configured without an
address and/or a prefix. Stateless address autoconfiguration requires
no manual configuration of hosts, minimal (if any) configuration of
routers, and no additional servers. A primary interface (lanX:0) is
automatically assigned a link-local address by the system when the
interface is configured. A link-local address comprises the wellknown
link-local prefix FE80::/10 and the interface identifier, which
is typically 64 bits long and is based on EUI-64 identifiers. The
link-local address allows automatic discovery of other hosts and
routers on the same link, using the Neighbor Discovery Protocol (see
NDP(7P)). The link-local address can be used as the source address to
communicate with other nodes when no routers are present. If a router
on the local link advertises prefixes in router advertisements, the
host autoconfigures its secondary interfaces and its default gateway.
The address of an autoconfigured secondary interface is formed by
prepending the prefix received from the router to the interface
identifier, the same interface identifier that is used in forming the
primary interface.
Manual Address Configuration:
IPv6 interfaces can also be configured with manually assigned
addresses and/or prefixes. A primary interface must be configured
with a link-local address and the prefix must not be specified. The
prefix is always 10. The universal/local bit, the U bit, of the
interface identifier must be 0, per section 2.5.1 of RFC 2373.
Accordingly, a manually assigned address for a primary interface must
have the following pattern: FE80::xMxx:xxxx:xxxx:xxxx where x is any
hexadecimal digit, and M must be 0, 1, 4, 5, 8, 9, C, or D.
When a primary interface is configured with a manually assigned
address, secondary interfaces will be autoconfigured if the host
receives prefixes from router advertisements. The addresses on the
secondary interfaces will be derived from the interface identifier
portion of manually configured address in the primary interface.
When a secondary interface is configured with a manually assigned
address, and if the user chooses an IP index number that has been used
for an autoconfigured secondary interface, the manual configuration
overwrites the autoconfiguration. When this happens, network
connectivity through the overwritten autoconfigured IP address is
temporarily lost. At a later time, when the host receives the next
router advertisement, the host will bring up another secondary
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interface with a different IP index number, but with the same IP
address, and network connectivity through that IP address is restored.
Normally, a user can avoid this by checking used IP index numbers.
However, there is always a possibility that address autoconfiguration
due to router advertisement is happening concurrently while the user
manually configures secondary interfaces.
To disable communication through a specific IP address on an
autoconfigured secondary interface, that secondary interface should be
marked down, not removed or overwritten with a different IP address.
If that interface is removed or overwritten, the host will reconfigure
another secondary interface with the same IP address when it receives
the next router advertisement. Alternatively, the router can be
configured to stop advertising the prefix that corresponds to the
offending IP address.
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IPv6 interface flags displayed:
An IPv6 interface may have three new flags that are not present in an
IPv4 interface: TUNNEL, AUTO, and ONLINK. The TUNNEL flag is set for
the tunnel interfaces. The AUTO flag is set for autoconfigured
secondary interfaces. The ONLINK flag is set for interfaces with IP
addresses that can be reached without going through a router.
Examples:
Stateless address autoconfiguration with link-local address
ifconfig lan0 inet6 up
Manual configuration for a primary interface with link-local address
ifconfig lan0 inet6 fe80::1 up
Manual configuration for a secondary interface with link-local address
ifconfig lan0:1 inet6 fe80::3 up
Manual configuration for a secondary interface with global address
ifconfig lan0:3 inet6 2222::4 up
Tunnel interface configuration:
HP-UX supports "IP6-in-IP" configured tunnels as specified in RFC
2893, "IP-in-IP6" and "IP6-in-IP6" configured tunnels as specified in
RFC 2473, and 6to4 automatic tunnel as specified in RFC 3056.
IP6-in-IP tunnel interface configuration:
"IP6-in-IP" configured tunnel allows dual stack IPv6/IPv4 nodes to
communicate over an IPv4 infrastructure, by encapsulating the IPv6
packet inside an IPv4 header. The tunnel configuration must be done
on both the local (tunnel entry-point) system and the remote (tunnel
exit-point) system. "IP6-in-IP" tunnels can be configured as shown
below:
ifconfig iptu0 inet6 tunnel ip6inip [source_link-local_address] \
[destination_link-local_address] tsrc tunnel_local_IPv4_address \
tdst tunnel_remote_IPv4_address up
The source and destination link-local IPv6 addresses of the tunnel
interface are optional; if they are not specified, they will be
autoconfigured based on the tunnel_local_IPv4_address and
tunnel_remote_IPv4_address, respectively.
The tunnel_local_IPv4_address should be an address configured on the
local system, and tunnel_remote_IPv4_address should be an address
configured on the remote system.
Example. On the local system:
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# ifconfig iptu0 inet6 tunnel ip6inip tsrc 192.168.1.1 \
tdst 192.168.2.2 up
Example. On the remote system:
# ifconfig iptu0 inet6 tunnel ip6inip tsrc 192.168.2.2 \
tdst 192.168.1.1 up
If multiple tunnels are configured with the same
tunnel_local_IPv4_address, autoconfiguration of only the first tunnel
will succeed. Other tunnels should be manually configured with linklocal
addresses.
Manual link-local addresses can be assigned to the tunnel interface as
shown below:
# ifconfig iptu0 inet6 tunnel ip6inip fe80::1 fe80::2 \
tsrc 10.10.1.1 tdst 10.10.2.2 up
Secondary addresses to the tunnel interfaces can be assigned as shown
below:
# ifconfig iptu0:1 inet6 2ffe::1 3ffe::1 up
IP-in-IP6 tunnel interface configuration:
"IP-in-IP6" tunnel configuration allows transmission of IPv4 packets
encapsulated in an IPv6 header. "IP-in-IP6" tunnels can be configured
as shown below:
ifconfig ip6tu0 inet tunnel ipinip6 source_IPv4_address \
destination_IPv4_address tsrc tunnel_local_IPv6_address \
tdst tunnel_remote_IPv6_address up
The tunnel_local_IPv6_address should be an address configured on the
local system, and tunnel_remote_IPv6_address should be an address
configured on the remote system. The tunnel configuration should be
done on both the local and the remote systems.
Example. On the local system:
# ifconfig ip6tu0 inet tunnel ipinip6 10.10.1.1 10.10.2.2 \
tsrc 2ffe::1 tdst 3ffe::1 up
Example. On the remote system:
# ifconfig ip6tu0 inet tunnel ipinip6 10.10.2.2 10.10.1.1 \
tsrc 3ffe::1 tdst 2ffe::1 up
IP6-in-IP6 tunnel interface configuration:
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"IP6-in-IP6" tunnel configuration allows transmission of IPv6 packets
encapsulated in an IPv6 header. "IP6-in-IP6" tunnels can be
configured as shown below:
ifconfig ip6tu0 inet6 tunnel ip6inip6 source_link-local_address \
destination_link-local_address tsrc tunnel_local_IPv6_address \
tdst tunnel_remote_IPv6_address up
The tunnel_local_IPv6_address should be an address configured on the
local system, and tunnel_remote_IPv6_address should be an address
configured on the remote system. The tunnel configuration should be
done on both the local and the remote systems.
Example. On the local system:
# ifconfig ip6tu1 inet6 tunnel ip6inip6 fe80::1 fe80::2 \
tsrc 2ffe::1 tdst 3ffe::1 up
Example. On the remote system:
# ifconfig ip6tu1 inet6 tunnel ip6inip6 fe80::2 fe80::1 \
tsrc 3ffe::1 tdst 2ffe::1 up
6to4 tunnel interface configuration:
6to4 tunnel configuration allows automatic tunneling of IPv6 packets
encapsulated in an IPv4 header over an IPv4 infrastructure. 6to4
tunnel interface can be configured as shown below:
ifconfig iptu1 inet6 tunnel 6to4 [6to4_primary_address] \
tsrc tunnel_local_IPv4_address up
The tunnel_local_IPv4_address should be a global IPv4 address. The
primary address of the 6to4 interface should be a 6to4 address and not
a link-local address. The 6to4 primary address is optional, if it is
not specified, a 6to4 address will be autoconfigured based on
tunnel_local_IPv4_address.
Example:
# ifconfig iptu1 inet6 tunnel 6to4 tsrc 15.13.136.204 up
A 6to4 address can be manually assigned as shown below:
# ifconfig iptu1 inet6 tunnel 6to4 2002:f0d:88cc::1 \
tsrc 15.13.136.204 up
To advertise a 6to4 prefix, see rtradvd(1M).
DIAGNOSTICS [Toc] [Back]
Messages indicate if the specified interface does not exist, the
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requested address is unknown, or the user is not privileged and tried
to alter an interface's configuration.
AUTHOR [Toc] [Back]
ifconfig was developed by HP and the University of California,
Berkeley.
SEE ALSO [Toc] [Back]
netstat(1), lanscan(1M), route(1M), inet(3N), inet6(3N), hosts(4),
routing(7), rtradvd(1M), NDP(7P).
IP Version 6 Addressing Architecture, RFC2373, Hinden, Derring.
Transition Mechanisms for IPv6 Hosts and Routers, RFC 2893, Gilligan,
Nordmark.
Generic Packet Tunneling in IPv6 Specification, RFC 2473, Conta,
Deering.
Connection of IPv6 Domains via IPv4 Clouds, RFC 3056, Carpenter,
Moore.
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