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14       This  program  is obsolete!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  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).
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62       up     This  flag  causes the interface to be activated.  It is implic‐
63              itly specified if an address is assigned to the interface.
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65       down   This flag causes the driver for this interface to be shut down.
66
67       [-]arp Enable or disable the use of the ARP protocol on this interface.
68
69       [-]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.
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74       [-]allmulti
75              Enable or disable all-multicast mode.  If selected,  all  multi‐
76              cast packets on the network will be received by the interface.
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78       mtu N  This parameter sets the Maximum Transfer Unit (MTU) of an inter‐
79              face.
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81       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
86       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.
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91       add addr/prefixlen
92              Add an IPv6 address to an interface.
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94       del addr/prefixlen
95              Remove an IPv6 address from an interface.
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97       tunnel ::aa.bb.cc.dd
98              Create a new SIT (IPv6-in-IPv4) device, tunnelling to the  given
99              destination.
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101       irq addr
102              Set the interrupt line used by this device.  Not all devices can
103              dynamically change their IRQ setting.
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105       io_addr addr
106              Set the start address in I/O space for this device.
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108       mem_start addr
109              Set the start address for shared memory  used  by  this  device.
110              Only a few devices need this.
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112       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
121       [-]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
126       [-]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
135       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
143       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.
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148       address
149              The IP address to be assigned to this interface.
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151       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.
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NOTES

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
164       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
169       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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FILES

175       /proc/net/dev
176       /proc/net/if_inet6
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BUGS

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

189       ip(8), iptables(8)
190       http://physics.nist.gov/cuu/Units/binary.html  -  Prefixes  for  binary
191       multiples
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AUTHORS

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>
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202net-tools                         2008-10-03                       IFCONFIG(8)
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