1IFCONFIG(8) Linux Programmer's Manual IFCONFIG(8)
2
6 ifconfig - configure a network interface
7
10 ifconfig [interface]
11 ifconfig interface [aftype] options | address ...
12
15 This program is obsolete! For replacement check ip addr and ip link.
16 For statistics use ip -s link.
17
20 Ifconfig is used to configure the kernel-resident network interfaces.
21 It is used at boot time to set up interfaces as necessary. After that,
22 it is usually only needed when debugging or when system tuning is
23 needed.
24 If no arguments are given, ifconfig displays the status of the cur‐
26 rently active interfaces. If a single interface argument is given, it
27 displays the status of the given interface only; if a single -a argu‐
28 ment is given, it displays the status of all interfaces, even those
29 that are down. Otherwise, it configures an interface.
30
33 If the first argument after the interface name is recognized as the
34 name of a supported address family, that address family is used for
35 decoding and displaying all protocol addresses. Currently supported
36 address families include inet (TCP/IP, default), inet6 (IPv6), ax25
37 (AMPR Packet Radio), ddp (Appletalk Phase 2), ipx (Novell IPX) and
38 netrom (AMPR Packet radio). All numbers supplied as parts in IPv4 dot‐
39 ted decimal notation may be decimal, octal, or hexadecimal, as speci‐
40 fied in the ISO C standard (that is, a leading 0x or 0X implies hexa‐
41 decimal; otherwise, a leading '0' implies octal; otherwise, the number
42 is interpreted as decimal). Use of hexamedial and octal numbers is not
43 RFC-compliant and therefore its use is discouraged and may go away.
44
47 interface
48 The name of the interface. This is usually a driver name fol‐
49 lowed by a unit number, for example eth0 for the first Ethernet
50 interface.
51 up This flag causes the interface to be activated. It is implic‐
53 itly specified if an address is assigned to the interface.
54 down This flag causes the driver for this interface to be shut down.
56 [-]arp Enable or disable the use of the ARP protocol on this interface.
58 [-]promisc
60 Enable or disable the promiscuous mode of the interface. If
61 selected, all packets on the network will be received by the
62 interface.
63 [-]allmulti
65 Enable or disable all-multicast mode. If selected, all multi‐
66 cast packets on the network will be received by the interface.
67 metric N
69 This parameter sets the interface metric. It is not available
70 under GNU/Linux.
71 mtu N This parameter sets the Maximum Transfer Unit (MTU) of an inter‐
73 face.
74 dstaddr addr
76 Set the remote IP address for a point-to-point link (such as
77 PPP). This keyword is now obsolete; use the pointopoint keyword
78 instead.
79 netmask addr
81 Set the IP network mask for this interface. This value defaults
82 to the usual class A, B or C network mask (as derived from the
83 interface IP address), but it can be set to any value.
84 add addr/prefixlen
86 Add an IPv6 address to an interface.
87 del addr/prefixlen
89 Remove an IPv6 address from an interface.
90 tunnel ::aa.bb.cc.dd
92 Create a new SIT (IPv6-in-IPv4) device, tunnelling to the given
93 destination.
94 irq addr
96 Set the interrupt line used by this device. Not all devices can
97 dynamically change their IRQ setting.
98 io_addr addr
100 Set the start address in I/O space for this device.
101 mem_start addr
103 Set the start address for shared memory used by this device.
104 Only a few devices need this.
105 media type
107 Set the physical port or medium type to be used by the device.
108 Not all devices can change this setting, and those that can vary
109 in what values they support. Typical values for type are
110 10base2 (thin Ethernet), 10baseT (twisted-pair 10Mbps Ethernet),
111 AUI (external transceiver) and so on. The special medium type
112 of auto can be used to tell the driver to auto-sense the media.
113 Again, not all drivers can do this.
114 [-]broadcast [addr]
116 If the address argument is given, set the protocol broadcast
117 address for this interface. Otherwise, set (or clear) the
118 IFF_BROADCAST flag for the interface.
119 [-]pointopoint [addr]
121 This keyword enables the point-to-point mode of an interface,
122 meaning that it is a direct link between two machines with
123 nobody else listening on it.
124 If the address argument is also given, set the protocol address
125 of the other side of the link, just like the obsolete dstaddr
126 keyword does. Otherwise, set or clear the IFF_POINTOPOINT flag
127 for the interface.
128 hw class address
130 Set the hardware address of this interface, if the device driver
131 supports this operation. The keyword must be followed by the
132 name of the hardware class and the printable ASCII equivalent of
133 the hardware address. Hardware classes currently supported
134 include ether (Ethernet), ax25 (AMPR AX.25), ARCnet and netrom
135 (AMPR NET/ROM).
136 multicast
138 Set the multicast flag on the interface. This should not nor‐
139 mally be needed as the drivers set the flag correctly them‐
140 selves.
141 address
143 The IP address to be assigned to this interface.
144 txqueuelen length
146 Set the length of the transmit queue of the device. It is useful
147 to set this to small values for slower devices with a high
148 latency (modem links, ISDN) to prevent fast bulk transfers from
149 disturbing interactive traffic like telnet too much.
150
153 Since kernel release 2.2 there are no explicit interface statistics for
154 alias interfaces anymore. The statistics printed for the original
155 address are shared with all alias addresses on the same device. If you
156 want per-address statistics you should add explicit accounting rules
157 for the address using the ipchains(8) command.
158 Interrupt problems with Ethernet device drivers fail with EAGAIN. See
160 http://www.scyld.com/expert/irq-conflict.html for more information.
161
164 /proc/net/socket
165 /proc/net/dev
166 /proc/net/if_inet6
167
170 Ifconfig uses obsolete kernel interface. It uses the ioctl access
171 method to get the full address information, which limits hardware
172 addresses to 8 bytes. Since an Infiniband address is 20 bytes, only
173 the first 8 bytes of Infiniband address are displayed.
174 While appletalk DDP and IPX addresses will be displayed they cannot be
176 altered by this command.
177
180 ip(8)
181
184 Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
185 Alan Cox, <Alan.Cox@linux.org>
186 Phil Blundell, <Philip.Blundell@pobox.com>
187 Andi Kleen
188net-tools 14 August 2000 IFCONFIG(8)