{ "mode": "man", "parameter": "ifconfig", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/ifconfig/8/json", "generated": "2026-09-16T19:19:38Z", "synopsis": "", "sections": { "NAME": { "content": "ifconfig - configure a network interface\n", "subsections": [] }, "SYNOPSIS": { "content": "", "subsections": [ { "name": "ifconfig [-v] [-a] [-s] [interface]", "content": "" }, { "name": "ifconfig [-v] interface [aftype] options | address ...", "content": "" } ] }, "DESCRIPTION": { "content": "Ifconfig is used to configure the kernel-resident network interfaces. It is used at boot\ntime to set up interfaces as necessary. After that, it is usually only needed when debugging\nor when system tuning is needed.\n\nIf no arguments are given, ifconfig displays the status of the currently active interfaces.\nIf a single interface argument is given, it displays the status of the given interface only;\nif a single -a argument is given, it displays the status of all interfaces, even those that\nare down. Otherwise, it configures an interface.\n\n", "subsections": [] }, "Address Families": { "content": "If the first argument after the interface name is recognized as the name of a supported ad‐\ndress family, that address family is used for decoding and displaying all protocol addresses.\nCurrently supported address families include inet (TCP/IP, default), inet6 (IPv6), ax25 (AMPR\nPacket Radio), ddp (Appletalk Phase 2), ipx (Novell IPX) and netrom (AMPR Packet radio). All\nnumbers supplied as parts in IPv4 dotted decimal notation may be decimal, octal, or hexadeci‐\nmal, as specified in the ISO C standard (that is, a leading 0x or 0X implies hexadecimal;\notherwise, a leading '0' implies octal; otherwise, the number is interpreted as decimal). Use\nof hexadecimal and octal numbers is not RFC-compliant and therefore its use is discouraged.\n", "subsections": [] }, "OPTIONS": { "content": "", "subsections": [ { "name": "-a", "content": "", "flag": "-a" }, { "name": "-s", "content": "", "flag": "-s" }, { "name": "-v", "content": "", "flag": "-v" }, { "name": "interface", "content": "The name of the interface. This is usually a driver name followed by a unit number,\nfor example eth0 for the first Ethernet interface. If your kernel supports alias in‐\nterfaces, you can specify them with syntax like eth0:0 for the first alias of eth0.\nYou can use them to assign more addresses. To delete an alias interface use ifconfig\neth0:0 down. Note: for every scope (i.e. same net with address/netmask combination)\nall aliases are deleted, if you delete the first (primary).\n\nup This flag causes the interface to be activated. It is implicitly specified if an ad‐\ndress is assigned to the interface; you can suppress this behavior when using an alias\ninterface by appending an - to the alias (e.g. eth0:0-). It is also suppressed when\nusing the IPv4 0.0.0.0 address as the kernel will use this to implicitly delete alias\ninterfaces.\n\ndown This flag causes the driver for this interface to be shut down.\n\n[-]arp Enable or disable the use of the ARP protocol on this interface.\n" }, { "name": "[-]promisc", "content": "Enable or disable the promiscuous mode of the interface. If selected, all packets on\nthe network will be received by the interface.\n" }, { "name": "[-]allmulti", "content": "Enable or disable all-multicast mode. If selected, all multicast packets on the net‐\nwork will be received by the interface.\n\nmtu N This parameter sets the Maximum Transfer Unit (MTU) of an interface.\n" }, { "name": "dstaddr addr", "content": "Set the remote IP address for a point-to-point link (such as PPP). This keyword is\nnow obsolete; use the pointopoint keyword instead.\n" }, { "name": "netmask addr", "content": "Set the IP network mask for this interface. This value defaults to the usual class A,\nB or C network mask (as derived from the interface IP address), but it can be set to\nany value.\n" }, { "name": "add addr/prefixlen", "content": "Add an IPv6 address to an interface.\n" }, { "name": "del addr/prefixlen", "content": "Remove an IPv6 address from an interface.\n" }, { "name": "tunnel ::aa.bb.cc.dd", "content": "Create a new SIT (IPv6-in-IPv4) device, tunnelling to the given destination.\n" }, { "name": "irq addr", "content": "Set the interrupt line used by this device. Not all devices can dynamically change\ntheir IRQ setting.\n" }, { "name": "io_addr addr", "content": "Set the start address in I/O space for this device.\n" }, { "name": "mem_start addr", "content": "Set the start address for shared memory used by this device. Only a few devices need\nthis.\n" }, { "name": "media type", "content": "Set the physical port or medium type to be used by the device. Not all devices can\nchange this setting, and those that can vary in what values they support. Typical\nvalues for type are 10base2 (thin Ethernet), 10baseT (twisted-pair 10Mbps Ethernet),\nAUI (external transceiver) and so on. The special medium type of auto can be used to\ntell the driver to auto-sense the media. Again, not all drivers can do this.\n" }, { "name": "[-]broadcast [addr]", "content": "If the address argument is given, set the protocol broadcast address for this inter‐\nface. Otherwise, set (or clear) the IFFBROADCAST flag for the interface.\n" }, { "name": "[-]pointopoint [addr]", "content": "This keyword enables the point-to-point mode of an interface, meaning that it is a di‐\nrect link between two machines with nobody else listening on it.\nIf the address argument is also given, set the protocol address of the other side of\nthe link, just like the obsolete dstaddr keyword does. Otherwise, set or clear the\nIFFPOINTOPOINT flag for the interface.\n" }, { "name": "hw class address", "content": "Set the hardware address of this interface, if the device driver supports this opera‐\ntion. The keyword must be followed by the name of the hardware class and the print‐\nable ASCII equivalent of the hardware address. Hardware classes currently supported\ninclude ether (Ethernet), ax25 (AMPR AX.25), ARCnet and netrom (AMPR NET/ROM).\n" }, { "name": "multicast", "content": "Set the multicast flag on the interface. This should not normally be needed as the\ndrivers set the flag correctly themselves.\n" }, { "name": "address", "content": "The IP address to be assigned to this interface.\n" }, { "name": "txqueuelen length", "content": "Set the length of the transmit queue of the device. It is useful to set this to small\nvalues for slower devices with a high latency (modem links, ISDN) to prevent fast bulk\ntransfers from disturbing interactive traffic like telnet too much.\n\nname newname\nChange the name of this interface to newname. The interface must be shut down first.\n" } ] }, "NOTES": { "content": "Since kernel release 2.2 there are no explicit interface statistics for alias interfaces any‐\nmore. The statistics printed for the original address are shared with all alias addresses on\nthe same device. If you want per-address statistics you should add explicit accounting rules\nfor the address using the iptables(8) command.\n\nInterrupt problems with Ethernet device drivers fail with EAGAIN (SIOCSIIFLAGS: Resource tem‐\nporarily unavailable) it is most likely a interrupt conflict. See http://www.scyld.com/ex‐\npert/irq-conflict.html for more information.\n", "subsections": [] }, "FILES": { "content": "/proc/net/dev\n/proc/net/ifinet6\n", "subsections": [] }, "BUGS": { "content": "Ifconfig uses the ioctl access method to get the full address information, which limits hard‐\nware addresses to 8 bytes. Because Infiniband hardware address has 20 bytes, only the first\n8 bytes are displayed correctly. Please use ip link command from iproute2 package to display\nlink layer informations including the hardware address.\n\nWhile appletalk DDP and IPX addresses will be displayed they cannot be altered by this com‐\nmand.\n", "subsections": [] }, "SEE ALSO": { "content": "route(8), netstat(8), arp(8), rarp(8), iptables(8), ifup(8), interfaces(5)\nhttp://physics.nist.gov/cuu/Units/binary.html - Prefixes for binary multiples\n", "subsections": [] }, "AUTHORS": { "content": "Fred N. van Kempen, \nAlan Cox, \nPhil Blundell, \nAndi Kleen\nBernd Eckenfels, \n\nnet-tools 2008-10-03 IFCONFIG(8)", "subsections": [] } }, "summary": "ifconfig - configure a network interface", "flags": [ { "flag": "-a", "long": null, "arg": null, "description": "" }, { "flag": "-s", "long": null, "arg": null, "description": "" }, { "flag": "-v", "long": null, "arg": null, "description": "" }, { "flag": "", "long": null, "arg": null, "description": "Enable or disable the promiscuous mode of the interface. If selected, all packets on the network will be received by the interface." }, { "flag": "", "long": null, "arg": null, "description": "Enable or disable all-multicast mode. If selected, all multicast packets on the net‐ work will be received by the interface. mtu N This parameter sets the Maximum Transfer Unit (MTU) of an interface." }, { "flag": "", "long": null, "arg": null, "description": "If the address argument is given, set the protocol broadcast address for this inter‐ face. Otherwise, set (or clear) the IFFBROADCAST flag for the interface." }, { "flag": "", "long": null, "arg": null, "description": "This keyword enables the point-to-point mode of an interface, meaning that it is a di‐ rect link between two machines with nobody else listening on it. If the address argument is also given, set the protocol address of the other side of the link, just like the obsolete dstaddr keyword does. Otherwise, set or clear the IFFPOINTOPOINT flag for the interface." } ], "examples": [], "see_also": [ { "name": "route", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/route/8/json" }, { "name": "netstat", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/netstat/8/json" }, { "name": "arp", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/arp/8/json" }, { "name": "rarp", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/rarp/8/json" }, { "name": "iptables", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/iptables/8/json" }, { "name": "ifup", "section": "8", "url": "https://www.chedong.com/phpMan.php/man/ifup/8/json" }, { "name": "interfaces", "section": "5", "url": "https://www.chedong.com/phpMan.php/man/interfaces/5/json" } ] }