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14 This program is obsolete!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 eth0:0 for the first alias of eth0. You can
57 use them to assign a second address. To delete an alias inter‐
58 face use ifconfig eth0:0 down. Note: for every scope (i.e. same
59 net with address/netmask combination) all aliases are deleted,
60 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.
64 down This flag causes the driver for this interface to be shut down.
66 [-]arp Enable or disable the use of the ARP protocol on this interface.
68 [-]promisc
70 Enable or disable the promiscuous mode of the interface. If
71 selected, all packets on the network will be received by the
72 interface.
73 [-]allmulti
75 Enable or disable all-multicast mode. If selected, all multi‐
76 cast packets on the network will be received by the interface.
77 mtu N This parameter sets the Maximum Transfer Unit (MTU) of an inter‐
79 face.
80 dstaddr addr
82 Set the remote IP address for a point-to-point link (such as
83 PPP). This keyword is now obsolete; use the pointopoint keyword
84 instead.
85 netmask addr
87 Set the IP network mask for this interface. This value defaults
88 to the usual class A, B or C network mask (as derived from the
89 interface IP address), but it can be set to any value.
90 add addr/prefixlen
92 Add an IPv6 address to an interface.
93 del addr/prefixlen
95 Remove an IPv6 address from an interface.
96 tunnel ::aa.bb.cc.dd
98 Create a new SIT (IPv6-in-IPv4) device, tunnelling to the given
99 destination.
100 irq addr
102 Set the interrupt line used by this device. Not all devices can
103 dynamically change their IRQ setting.
104 io_addr addr
106 Set the start address in I/O space for this device.
107 mem_start addr
109 Set the start address for shared memory used by this device.
110 Only a few devices need this.
111 media type
113 Set the physical port or medium type to be used by the device.
114 Not all devices can change this setting, and those that can vary
115 in what values they support. Typical values for type are
116 10base2 (thin Ethernet), 10baseT (twisted-pair 10Mbps Ethernet),
117 AUI (external transceiver) and so on. The special medium type
118 of auto can be used to tell the driver to auto-sense the media.
119 Again, not all drivers can do this.
120 [-]broadcast [addr]
122 If the address argument is given, set the protocol broadcast
123 address for this interface. Otherwise, set (or clear) the
124 IFF_BROADCAST flag for the interface.
125 [-]pointopoint [addr]
127 This keyword enables the point-to-point mode of an interface,
128 meaning that it is a direct link between two machines with
129 nobody else listening on it.
130 If the address argument is also given, set the protocol address
131 of the other side of the link, just like the obsolete dstaddr
132 keyword does. Otherwise, set or clear the IFF_POINTOPOINT flag
133 for the interface.
134 hw class address
136 Set the hardware address of this interface, if the device driver
137 supports this operation. The keyword must be followed by the
138 name of the hardware class and the printable ASCII equivalent of
139 the hardware address. Hardware classes currently supported
140 include ether (Ethernet), ax25 (AMPR AX.25), ARCnet and netrom
141 (AMPR NET/ROM).
142 multicast
144 Set the multicast flag on the interface. This should not nor‐
145 mally be needed as the drivers set the flag correctly them‐
146 selves.
147 address
149 The IP address to be assigned to this interface.
150 txqueuelen length
152 Set the length of the transmit queue of the device. It is useful
153 to set this to small values for slower devices with a high
154 latency (modem links, ISDN) to prevent fast bulk transfers from
155 disturbing interactive traffic like telnet too much.
156
158 Since kernel release 2.2 there are no explicit interface statistics for
159 alias interfaces anymore. The statistics printed for the original
160 address are shared with all alias addresses on the same device. If you
161 want per-address statistics you should add explicit accounting rules
162 for the address using the iptables(8) command.
163 Since net-tools 1.60-4 ifconfig is printing byte counters and human
165 readable counters with IEC 60027-2 units. So 1 KiB are 2^10 byte. Note,
166 the numbers are truncated to one decimal (which can by quite a large
167 error if you consider 0.1 PiB is 112.589.990.684.262 bytes :)
168 Interrupt problems with Ethernet device drivers fail with EAGAIN (SIOC‐
170 SIIFLAGS: Resource temporarily unavailable) it is most likely a inter‐
171 rupt conflict. See http://www.scyld.com/expert/irq-conflict.html for
172 more information.
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175 /proc/net/dev
176 /proc/net/if_inet6
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179 Ifconfig uses the ioctl access method to get the full address informa‐
180 tion, which limits hardware addresses to 8 bytes. Because Infiniband
181 hardware address has 20 bytes, only the first 8 bytes are displayed
182 correctly. Please use ip link command from iproute2 package to display
183 link layer informations including the hardware address.
184 While appletalk DDP and IPX addresses will be displayed they cannot be
186 altered by this command.
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189 ip(8), iptables(8)
190 http://physics.nist.gov/cuu/Units/binary.html - Prefixes for binary
191 multiples
192
194 Fred N. van Kempen, <waltje@uwalt.nl.mugnet.org>
195 Alan Cox, <Alan.Cox@linux.org>
196 Phil Blundell, <Philip.Blundell@pobox.com>
197 Andi Kleen
198 Bernd Eckenfels, <net-tools@lina.inka.de>
199net-tools 2008-10-03 IFCONFIG(8)