1IFCONFIG(8)           Linux System Administrator's Manual          IFCONFIG(8)
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NAME

6       ifconfig - configure a network interface
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SYNOPSIS

9       ifconfig [-v] [-a] [-s] [interface]
10       ifconfig [-v] interface [aftype] options | address ...
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12

NOTE

14       This  program  is obsolete!  For replacement check ip addr and ip link.
15       For statistics use ip -s link.
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17

DESCRIPTION

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
24       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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30

Address Families

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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OPTIONS

45       -a     display  all  interfaces  which are currently available, even if
46              down
47
48       -s     display a short list (like netstat -i)
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50       -v     be more verbose for some error conditions
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52       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
62       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.
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69       down   This flag causes the driver for this interface to be shut down.
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71       [-]arp Enable or disable the use of the ARP protocol on this interface.
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73       [-]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
78       [-]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
82       mtu N  This parameter sets the Maximum Transfer Unit (MTU) of an inter‐
83              face.
84
85       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.
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90       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.
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95       add addr/prefixlen
96              Add an IPv6 address to an interface.
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98       del addr/prefixlen
99              Remove an IPv6 address from an interface.
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101       tunnel ::aa.bb.cc.dd
102              Create a new SIT (IPv6-in-IPv4) device, tunnelling to the  given
103              destination.
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105       irq addr
106              Set the interrupt line used by this device.  Not all devices can
107              dynamically change their IRQ setting.
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109       io_addr addr
110              Set the start address in I/O space for this device.
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112       mem_start addr
113              Set the start address for shared memory  used  by  this  device.
114              Only a few devices need this.
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116       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
125       [-]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
130       [-]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
139       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).
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147       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
152       address
153              The IP address to be assigned to this interface.
154
155       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.
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NOTES

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
168       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
173       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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FILES

179       /proc/net/dev
180       /proc/net/if_inet6
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BUGS

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.
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189       While appletalk DDP and IPX addresses will be displayed they cannot  be
190       altered by this command.
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SEE ALSO

193       ip(8), iptables(8)
194       http://physics.nist.gov/cuu/Units/binary.html  -  Prefixes  for  binary
195       multiples
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AUTHORS

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>
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206net-tools                         2008-10-03                       IFCONFIG(8)
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