SYNOPSIS
The ifconfig command assigns addresses to network interfaces. It
also displays network interfaces and configures network interface
parameters.
For IPv4 environments, use the following syntax:
ifconfig interface_id [address_family] [address[/bitmask] [dest_address]] [parameters]
For IPv6 environments, use the following syntax:
ifconfig interface_id address_family [[ip6prefix] address[/bitmask] [dest_address]] [parameters]
To display information about interfaces, use the following
syntaxes:
ifconfig -a [-d] [-u] [-v] [address_family]
ifconfig -l [-d] [-u] [-v] [address_family]
ifconfig [-v] interface-id [address_family]
1 – FLAGS
-a Displays information about all interfaces that are
configured on a system.
-d Displays information about interfaces that are down.
-l Displays interface names that are configured on a system.
-u Displays information about interfaces that are up.
-v Displays detailed information about interfaces, such as
hardware addresses and IPv6 timers.
2 – DESCRIPTION
The ifconfig utility defines the network address of each
interface when TCP/IP Services starts. After that, you can
use the ifconfig utility to display all interfaces that are
configured on a system, to redefine the address of an interface,
and to set other operating parameters.
NOTE
If you want to redefine the interface address or the
netmask, you should stop TCP/IP Services first. Otherwise,
any TCP/IP processes currently running will continue to use
the old address and netmask, and will fail.
Any user can query the status of a network interface; only
a privileged user can modify the configuration of network
interfaces.
You specify an interface with the following syntax:
ifconfig interface_id
This command displays the current configuration for the specified
network interface. Refer to the HP TCP/IP Services for OpenVMS
Management for information about how to obtain the interface_id.
3 – ARGUMENTS
address_family
Specifies the protocol family for which to report the
configuration details.
The following table lists valid values for address_
family:
Address Type Value
IPv4 inet
IPv6 inet6
When changing an interface configuration, if the
address family is not inet, you must specify an address
family, which may alter the interpretation of any
parameters that follow. You must specify an address
family because an interface can receive transmissions
in different protocols, each of which may require a
separate naming scheme.
address Specifies the network address of the interface being
configured. For the inet address family, the address
argument is either a hostname or an Internet address in
the standard dotted-decimal notation with or without
the optional Classless Interdomain Routing (CIDR)
bitmask (/bitmask). If using the bitmask argument,
do not use the netmask parameter.
For the inet6 address family, the address argument
is either a host name or the 128-bit IPv6 address, as
follows:
x:x:x:x:x:x:x:x
In this format, each x is the hexadecimal value of
a 16-bit portion of the address. An IPv6 address
typically consists of a 64-bit prefix followed by a
64-bit interface identifier. See the HP TCP/IP Services
for OpenVMS Guide to IPv6 manual for more information
on IPv6 addresses.
ip6prefix
Specifies that the address argument is an IPv6 prefix
and that the interface identifier is to be appended to
it to create a 128-bit IPv6 address when configuring an
address on the interface.
interface identifier
Identifies an interface on a subnet, and is typically
the interface's link-layer address. Most prefixes are
required to have 64-bit interface identifiers. For
48-bit MAC addresses, the interface identifier is
created by inserting the hexadecimal values of 0xFF
and 0xFE in the middle of the address and inverting
the universal/local bit (bit 7) in the resulting
64-bit address. For example, the 48-bit MAC address
0:0:f8:23:10:f3 becomes the 64-bit interface identifier
2:0:f8:ff:fe:23:10:f3.
dest_address
Specifies the address of the correspondent on the
remote end of a point-to-point link.
4 – PARAMETERS
abort Closes all TCP connections associated with a network
address. Use this parameter when removing aliases or
deleting network addresses. This prevents connections
from hanging when the network address is deleted.
alias alias_address[/bitmask]
Establishes an additional network address for this
interface. This can be useful when changing network
numbers and you want to continue to accept packets
addressed to the old interface.
If you do not specify a bitmask or netmask with the
alias address, the default netmask is based on the
alias address's network class.
If you are using the optional bitmask argument, do not
use the netmask argument.
This parameter has the following restrictions:
o You can specify only one alias alias_address
parameter for each ifconfig command line.
o You cannot specify an alias and a primary address on
the same command line.
-alias alias_address
Removes the network address specified. This can be
used either if you incorrectly specified an alias or
if an alias is no longer needed. The -alias parameter
functions in the same manner as the delete parameter.
aliaslist address_list[/bitmask]
Establishes a range of additional network addresses for
this interface. The range can be a comma-separated list
or a hyphenated list, and is inclusive. You can also
specify the optional CIDR bitmask (/bitmask) argument
at the end of the list. Do not use a comma-separated
list and a hyphenated list for a range. (IPv4 only)
-aliaslist
Removes a range of network addresses for this
interface. This can be useful when deleting network
numbers and you want to keep the primary interface
address. The alias list rules are the same as for the
aliaslist parameter. (IPv4 only)
allmulti Enables the reception of all multicast packets.
-allmulti
Disables the reception of all multicast packets.
arp Enables the use of the Address Resolution Protocol
(ARP) in mapping between network-level addresses and
link-level addresses. This parameter is on by default.
-arp Disables the use of the ARP. Use of this parameter is
not recommended.
broadcast broad_address
Specifies the address to use to represent broadcasts
to the network. The default broadcast address is
the address with a host part consisting of all 1s
(ones). Note that the computation of the host part
is dependent on netmask. (See the description of the
netmask parameter for more information).
delete [net_address]
Removes the network address specified. Use this
parameter if you incorrectly specified an alias, or
if it was no longer needed. If you incorrectly set an
NS address, specifying the host portion, remove all NS
addresses to respecify the host portion.
If no address is specified, all network addresses for
the interface are deleted.
Be careful when you use this parameter. If you either
specify the network address before the delete parameter
or specify no network address after the delete
parameter, all IPv4 and IPv6 network addresses for
the interface and IPv6 routes are deleted. IPv4 routes
are not deleted.
down Marks an interface as not working (down), which keeps
the system from trying to transmit messages through
that interface. If possible, the ifconfig command
also resets the interface to disable reception of
messages. Routes that use the interface, however, are
not automatically disabled.
ip6dadtries value
Specifies the number of consecutive Neighbor
Solicitation messages that your system transmits while
it performs Duplicate Address Detection on a tentative
address. (IPv6 only)
ip6hoplimit hops
Sets the default number of hops to be included in
transmitted unicast IP packets. (IPv6 only)
ip6interfaceid id
Overrides that default interface ID, which depends on
the underlying link type (for example, Ethernet, FDDI,
and Token Ring), and specifies id as the interface
ID. For example, if your system has the Ethernet
hardware address 08-00-2b-2a-1e-d3, the following
command generates the inet6 link-local address
fe80::a00:2bff:fe2a:1ed3 for the interface:
ifconfig ln0 ipv6
On the same system, the following command generates the
IPv6 interface ID abcd:1234 for the interface:
ifconfig ln0 ip6interfaceid ::abcd:1234 ipv6
(IPv6 only)
ip6mtu mtu_value
Alters the maximum transfer unit (MTU) for messages
that your system transmits on the link. (IPv6 only)
ip6nonud Disables Neighbor Unreachability Detection (NUD) on the
interface. (IPv6 only)
ip6reachabletime time
Sets the time, in milliseconds, that your system con
siders a neighbor is reachable after your system
receives a reachability confirmation message. (IPv6
only)
ip6retranstimer value
Sets the time interval, in milliseconds, between
Neighbor Solicitation messages to a neighbor. (IPv6
only)
ipmtu mtu_value
Alters the size of the maximum transfer unit (MTU)
for messages that your system transmits. It might
be necessary to reduce the MTU size so that bridges
connecting token rings can transfer frames without
error.
ipv6 Initializes IPv6-related data structures and assigns an
IPv6 link-local address to the interface. (IPv6 only)
-ipv6 Removes any IPv6 configuration associated with the
interface, including all IPv6 addresses and IPv6
routes through the interface. This is equivalent to
the following command:
ifconfig interface inet6d delete
(IPv6 only)
metric number
Sets the routing metric, or number of hops, for the
interface to the value of number. The default value
is 0 (zero) if number is not specified, indicating
that both hosts are on the same network. The routing
metric is used by ROUTED and GATED, with higher metrics
indicating that the route is less favorable.
ndna [ address ]
Sends an unsolicited ICMPv6, Neighbor Advertisement
for each address configured on the interface. If the
address is provided, then send a Neighbor Advertisment
for the specified address only. If a DNS alias is used
as the address, a Neighbor Advertisement is sent for
each address that comprises the DNS alias name. (IPv6
only)
netmask mask
Specifies how much of the address to reserve for
subdividing networks into sub-networks. This parameter
can only be used with an address family of inet. Do not
use this parameter if you are specifying the CIDR mask
(/bitmask) with the address argument, alias parameter,
or aliaslist parameter.
The mask variable includes both 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 beginning with
0x, in the standard Internet dotted-decimal notation,
or beginning with a name.
The mask contains 1s (ones) for the bit positions in
the 32-bit address that are reserved for the network
and subnet parts, and 0s (zeros) for the bit positions
that specify the host. The mask should contain at least
the standard network portion.
The default netmask is based on the address parameter's
network class. (IPv4 only)
up Marks an interface as working (up). This parameter is
used automatically when setting the first address for
an interface, or can be used to enable an interface
after an ifconfig down command. If the interface was
reset when previously marked with the parameter down
(see the following section for a description of this
parameter), the hardware will be reinitialized.
5 – DISPLAY_OPTIONS
When you issue the ifconfig command for an interface you might
see any of the following options displayed:
BROADCAST The interface supports broadcast packets. This is a
read-only option that is set by the driver.
LOOPBACK The interface is a loopback mode. Packets transmitted
on this interface will be looped back in the driver and
not be transmitted out on the network.
MULTICAST The interface supports multicast packets. This is a
read-only option that is set by the driver and does
not mean that a multicast address is configured for the
interface.
NOARP The interface is not using address resolution protocol
(ARP). It will neither transmit nor respond to ARP
requests.
NOCHECKSUM The interface does not perform checksums on transmitted
or received packets. Use this option only on very
reliable network media.
POINTOPOINTThe interface is point-to-point link. This is a read-
only option that is set by the driver.
RUNNING The driver has allocated resources for the interface,
and is ready to transmit and receive packets. This is a
read-only option that is set by the driver. It is not
applicable to loopback devices.
SIMPLEX The interface cannot receive its own transmissions.
This is a read-only option that is set by the driver.
6 – EXAMPLES
o To query the status of an interface we0, enter:
$ ifconfig we0
o To configure the local loopback interface, enter:
$ ifconfig lo0 inet 127.0.0.1 up
Only a privileged user can modify the configuration of a
network interface.
o To configure a ie0 interface, enter:
$ ifconfig ie0 212.232.32.1/22
The broadcast address is 212.232.35.255 as the 22-bit mask
specifies four Class C networks.
o To configure an address that is not protected by failSAFE IP,
enter:
$ ifconfig -fs ie0 210.208.19.3/16
o To configure an alias address with a home interface, so that
failSAFE IP will attempt to return the address to its home
after the home recovers from a failure, enter:
$ ifconfig we0 home alias 156.47.92.8/24
o To configure IPv6 on a ie0 interface, enter:
$ ifconfig ie0 ipv6 up
o To configure an IPv6 link-local alias address on interface
ie0, enter:
$ ifconfig ie0 inet6 alias fe80::202:a5ff:fe60:abcd
o To add alias 132.50.40.35 with a netmask of 255.255.255.0 in
CIDR format to interface we0, enter:
$ ifconfig we0 alias 132.50.40.35/24
o To add network addresses 40 through 50, inclusive, to subnets
18.240.32, 18.240.33, 18.240.34, 18.240.35, and 18.240.36
with a netmask of 255.255.255.0 in CIDR format to the we0
interface, enter:
$ ifconfig we0 aliaslist 132.240.32-36.40-50/24
o To add network addresses 40 through 50, inclusive, to
subnets 18.240.32, 18.240.64, and 18.240.96 with a netmask
of 255.255.255.0 in CIDR format to the we0 interface, enter:
$ ifconfig we0 aliaslist 132.240.32,64,96.40-50/24
To stop Ethernet interface we0, delete all addresses
associated with the interface, and close all TCP connections,
enter:
$ ifconfig we0 down delete abort
145.92.16.1: aborting 7 tcp connection(s)
o To delete the alias address 145.92.16.2 on interface we0 and
close all TCP connections, enter:
$ ifconfig we0 -alias 145.92.16.2 abort
145.92.16.2: aborting 2 tcp connection(s)
o To create an IPv6 address for prefix AB:CD:CE:AB, enter:
$ ifconfig we0 inet6 ip6prefix AB:CD:CE:AB::/64
o To force an interface into a failed state, enter:
$ ifconfig ie0 fail
Note that this causes all routes that use IE0 to be deleted.
o To force an interface to recover from a failed state, enter:
$ ifconfig ie0 -fail
Note that only interface routes are recovered. Other static
routes must be restored manually.
o To display the names of the interfaces on the system only,
enter:
$ ifconfig -l
IE0 IE1 IE2 IE3 LO0 TN0 TN1 WE0
o To display the hardware and IP address of interface we0,
enter:
$ ifconfig -v we0
we0: options=c63<UP,BROADCAST,NOTRAILERS,RUNNING,MULTICAST,SIMPLEX>
HWaddr 8:0:2b:9e:14:a2
inet 192.140.34.16 netmask ffffff00 broadcast 192.140.34.255 ipmtu 1500