1IFCONFIG(8) Linux System Administrator's Manual IFCONFIG(8)
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6 ifconfig - configure a network interface
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9 ifconfig [-v] [-a] [-s] [interface]
10 ifconfig [-v] interface [aftype] options | address ...
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14 This program is obsolete! For replacement check ip addr and ip link.
15 For statistics use ip -s link.
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19 Ifconfig is used to configure the kernel-resident network interfaces.
20 It is used at boot time to set up interfaces as necessary. After that,
21 it is usually only needed when debugging or when system tuning is
22 needed.
23 If no arguments are given, ifconfig displays the status of the cur‐
25 rently active interfaces. If a single interface argument is given, it
26 displays the status of the given interface only; if a single -a argu‐
27 ment is given, it displays the status of all interfaces, even those
28 that are down. Otherwise, it configures an interface.
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32 If the first argument after the interface name is recognized as the
33 name of a supported address family, that address family is used for
34 decoding and displaying all protocol addresses. Currently supported
35 address families include inet (TCP/IP, default), inet6 (IPv6), ax25
36 (AMPR Packet Radio), ddp (Appletalk Phase 2), ipx (Novell IPX) and
37 netrom (AMPR Packet radio). All numbers supplied as parts in IPv4 dot‐
38 ted decimal notation may be decimal, octal, or hexadecimal, as speci‐
39 fied in the ISO C standard (that is, a leading 0x or 0X implies hexa‐
40 decimal; otherwise, a leading '0' implies octal; otherwise, the number
41 is interpreted as decimal). Use of hexadecimal and octal numbers is not
42 RFC-compliant and therefore its use is discouraged.
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45 -a display all interfaces which are currently available, even if
46 down
47 -s display a short list (like netstat -i)
49 -v be more verbose for some error conditions
51 interface
53 The name of the interface. This is usually a driver name fol‐
54 lowed by a unit number, for example eth0 for the first Ethernet
55 interface. If your kernel supports alias interfaces, you can
56 specify them with syntax like eth0:0 for the first alias of
57 eth0. You can use them to assign more addresses. To delete an
58 alias interface use ifconfig eth0:0 down. Note: for every scope
59 (i.e. same net with address/netmask combination) all aliases are
60 deleted, if you delete the first (primary).
61 up This flag causes the interface to be activated. It is implic‐
63 itly specified if an address is assigned to the interface; you
64 can suppress this behavior when using an alias interface by
65 appending an - to the alias (e.g. eth0:0-). It is also sup‐
66 pressed when using the IPv4 0.0.0.0 address as the kernel will
67 use this to implicitly delete alias interfaces.
68 down This flag causes the driver for this interface to be shut down.
70 [-]arp Enable or disable the use of the ARP protocol on this interface.
72 [-]promisc
74 Enable or disable the promiscuous mode of the interface. If
75 selected, all packets on the network will be received by the
76 interface.
77 [-]allmulti
79 Enable or disable all-multicast mode. If selected, all multi‐
80 cast packets on the network will be received by the interface.
81 mtu N This parameter sets the Maximum Transfer Unit (MTU) of an inter‐
83 face.
84 dstaddr addr
86 Set the remote IP address for a point-to-point link (such as
87 PPP). This keyword is now obsolete; use the pointopoint keyword
88 instead.
89 netmask addr
91 Set the IP network mask for this interface. This value defaults
92 to the usual class A, B or C network mask (as derived from the
93 interface IP address), but it can be set to any value.
94 add addr/prefixlen
96 Add an IPv6 address to an interface.
97 del addr/prefixlen
99 Remove an IPv6 address from an interface.
100 tunnel ::aa.bb.cc.dd
102 Create a new SIT (IPv6-in-IPv4) device, tunnelling to the given
103 destination.
104 irq addr
106 Set the interrupt line used by this device. Not all devices can
107 dynamically change their IRQ setting.
108 io_addr addr
110 Set the start address in I/O space for this device.
111 mem_start addr
113 Set the start address for shared memory used by this device.
114 Only a few devices need this.
115 media type
117 Set the physical port or medium type to be used by the device.
118 Not all devices can change this setting, and those that can vary
119 in what values they support. Typical values for type are
120 10base2 (thin Ethernet), 10baseT (twisted-pair 10Mbps Ethernet),
121 AUI (external transceiver) and so on. The special medium type
122 of auto can be used to tell the driver to auto-sense the media.
123 Again, not all drivers can do this.
124 [-]broadcast [addr]
126 If the address argument is given, set the protocol broadcast
127 address for this interface. Otherwise, set (or clear) the
128 IFF_BROADCAST flag for the interface.
129 [-]pointopoint [addr]
131 This keyword enables the point-to-point mode of an interface,
132 meaning that it is a direct link between two machines with
133 nobody else listening on it.
134 If the address argument is also given, set the protocol address
135 of the other side of the link, just like the obsolete dstaddr
136 keyword does. Otherwise, set or clear the IFF_POINTOPOINT flag
137 for the interface.
138 hw class address
140 Set the hardware address of this interface, if the device driver
141 supports this operation. The keyword must be followed by the
142 name of the hardware class and the printable ASCII equivalent of
143 the hardware address. Hardware classes currently supported
144 include ether (Ethernet), ax25 (AMPR AX.25), ARCnet and netrom
145 (AMPR NET/ROM).
146 multicast
148 Set the multicast flag on the interface. This should not nor‐
149 mally be needed as the drivers set the flag correctly them‐
150 selves.
151 address
153 The IP address to be assigned to this interface.
154 txqueuelen length
156 Set the length of the transmit queue of the device. It is useful
157 to set this to small values for slower devices with a high
158 latency (modem links, ISDN) to prevent fast bulk transfers from
159 disturbing interactive traffic like telnet too much.
160
162 Since kernel release 2.2 there are no explicit interface statistics for
163 alias interfaces anymore. The statistics printed for the original
164 address are shared with all alias addresses on the same device. If you
165 want per-address statistics you should add explicit accounting rules
166 for the address using the iptables(8) command.
167 Since net-tools 1.60-4 ifconfig is printing byte counters and human
169 readable counters with IEC 60027-2 units. So 1 KiB are 2^10 byte. Note,
170 the numbers are truncated to one decimal (which can by quite a large
171 error if you consider 0.1 PiB is 112.589.990.684.262 bytes :)
172 Interrupt problems with Ethernet device drivers fail with EAGAIN (SIOC‐
174 SIIFLAGS: Resource temporarily unavailable) it is most likely a inter‐
175 rupt conflict. See http://www.scyld.com/expert/irq-conflict.html for
176 more information.
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179 /proc/net/dev
180 /proc/net/if_inet6
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183 Ifconfig uses the ioctl access method to get the full address informa‐
184 tion, which limits hardware addresses to 8 bytes. Because Infiniband
185 hardware address has 20 bytes, only the first 8 bytes are displayed
186 correctly. Please use ip link command from iproute2 package to display
187 link layer informations including the hardware address.
188 While appletalk DDP and IPX addresses will be displayed they cannot be
190 altered by this command.
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193 ip(8), iptables(8)
194 http://physics.nist.gov/cuu/Units/binary.html - Prefixes for binary
195 multiples
196
198 Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
199 Alan Cox, <Alan.Cox@linux.org>
200 Phil Blundell, <Philip.Blundell@pobox.com>
201 Andi Kleen
202 Bernd Eckenfels, <net-tools@lina.inka.de>
203net-tools 2008-10-03 IFCONFIG(8)