ifconfig command in Linux with Examples

2024-07-16 18:37| 来源: 网络整理| 查看: 265

ifconfig command in Linux with Examples Previous Next Name

ifconfig - configure a network interface

Synopsis ifconfig [-v] [-a] [-s] [interface] ifconfig [-v] interface [aftype] options | address ... Description

ifconfig command is used to configure the kernel-resident network interfaces. It is used at boot time to set up interfaces as necessary. After that, it is usually needed to query and manage network parameters. It is also required during debugging or when system tuning is needed.

If no arguments are given, ifconfig command displays the status of the currently active interfaces. If a single interface argument is given, it displays the status of the given interface only; in case of -a option, it displays the status of all interfaces, even those that are down. Otherwise, it configures an interface.

Options

ifconfig commands accepts following options and arguments:

-a display all interfaces which are currently available, even if down -s display a short list (like netstat -i) -v be more verbose for some error conditions interface The name of the interface. This is usually a driver name followed by a unit number, for example eth0 for the first Ethernet interface. If your kernel supports alias interfaces, you can specify them with eth0:0 for the first alias of eth0. You can use them to assign a second address. To delete an alias interface use ifconfig eth0:0 down. Note: for every scope (i.e. same net with address/netmask combination) all aliases are deleted, if you delete the first (primary). up This flag causes the interface to be activated. It is implicitly specified if an address is assigned to the interface. down This flag causes the driver for this interface to be shut down. [-]arp Enable or disable the use of the ARP protocol on this interface. [-]promisc Enable or disable the promiscuous mode of the interface. If selected, all packets on the network will be received by the interface. [-]allmulti Enable or disable all-multicast mode. If selected, all multicast packets on the network will be received by the interface. metric N This parameter sets the interface metric. mtu N This parameter sets the Maximum Transfer Unit (MTU) of an interface. dstaddr addr Set the remote IP address for a point-to-point link (such as PPP). This keyword is now obsolete; use the pointopoint keyword instead. netmask addr Set the IP network mask for this interface. This value defaults to the usual class A, B or C network mask (as derived from the interface IP address), but it can be set to any value. add addr/prefixlen Add an IPv6 address to an interface. del addr/prefixlen Remove an IPv6 address from an interface. tunnel aa.bb.cc.dd Create a new SIT (IPv6-in-IPv4) device, tunnelling to the given destination. irq addr Set the interrupt line used by this device. Not all devices can dynamically change their IRQ setting. io_addr addr Set the start address in I/O space for this device. mem_start addr Set the start address for shared memory used by this device. Only a few devices need this. address The IP address to be assigned to this interface. Examples

1. ifconfig command without any argument displays the details of all the active interfaces. This command also displays the assigned ip address of active interfaces. There could be interfaces that are active but they may not have been assigend an IP address.

$ ifconfig eth0: flags=4099 mtu 1500 ether 20:25:64:08:6a:a4 txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 device interrupt 20 memory 0xf7c00000-f7c20000 lo: flags=73 mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10 loop txqueuelen 1000 (Local Loopback) RX packets 5426 bytes 509075 (509.0 KB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 5426 bytes 509075 (509.0 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 wlan0: flags=4163 mtu 1500 inet 192.168.72.222 netmask 255.255.255.0 broadcast 192.168.72.255 inet6 2409:4053:2105:527d:db24:166e:345d:d48a prefixlen 64 scopeid 0x0 inet6 fe80::fa1c:1e5f:feac:5280 prefixlen 64 scopeid 0x20 inet6 2409:4053:2105:527d:c113:9da0:ddcc:2235 prefixlen 64 scopeid 0x0 ether a4:2b:8c:5f:19:0b txqueuelen 1000 (Ethernet) RX packets 15381 bytes 7488890 (7.4 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 16671 bytes 2821518 (2.8 MB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

2. Use -a option to display all network interfaces on the server even if the network interface is down.

$ ifconfig -a eth0: flags=4099 mtu 1500 ether 20:25:64:08:6a:a4 txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 device interrupt 20 memory 0xf7c00000-f7c20000 lo: flags=73 mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10 loop txqueuelen 1000 (Local Loopback) RX packets 5426 bytes 509075 (509.0 KB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 5426 bytes 509075 (509.0 KB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 sit0 Link encap:IPv6-in-IPv4 NOARP MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 RX bytes:0 (0.0 b) TX bytes:0 (0.0 b) wlan0: flags=4163 mtu 1500 inet 192.168.72.222 netmask 255.255.255.0 broadcast 192.168.72.255 inet6 2409:4053:2105:527d:db24:166e:345d:d48a prefixlen 64 scopeid 0x0 inet6 fe80::fa1c:1e5f:feac:5280 prefixlen 64 scopeid 0x20 inet6 2409:4053:2105:527d:c113:9da0:ddcc:2235 prefixlen 64 scopeid 0x0 ether a4:2b:8c:5f:19:0b txqueuelen 1000 (Ethernet) RX packets 15381 bytes 7488890 (7.4 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 16671 bytes 2821518 (2.8 MB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

We can see that sit0 interface is down, even then it is listed in the display.

3. Use -s option to display a short list, instead of all the details.

$ ifconfig -s Iface MTU RX-OK RX-ERR RX-DRP RX-OVR TX-OK TX-ERR TX-DRP TX-OVR Flg eth0 1500 0 0 0 0 0 0 0 0 BMU lo 65536 9696 0 0 0 9696 0 0 0 LRU wlan0 1500 32426 0 0 0 35073 0 0 0 BMRU

4. ifconfig command with interface name (wlan0) as an argument displays details of interface configuration.

$ ifconfig wlan0 wlan0: flags=4163 mtu 1500 inet 192.168.72.222 netmask 255.255.255.0 broadcast 192.168.72.255 inet6 2409:4053:2105:527d:db24:166e:345d:d48a prefixlen 64 scopeid 0x0 inet6 fe80::fa1c:1e5f:feac:5280 prefixlen 64 scopeid 0x20 inet6 2409:4053:2105:527d:c113:9da0:ddcc:2235 prefixlen 64 scopeid 0x0 ether a4:2b:8c:5f:19:0b txqueuelen 1000 (Ethernet) RX packets 39246 bytes 16139815 (16.1 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 42288 bytes 8517460 (8.5 MB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

4. ifconfig command along with down option can be used to deactivate a network interface. Use this command with root permissions.

$ sudo ifconfig enp0s25 down $ ifconfig lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:187930 errors:0 dropped:0 overruns:0 frame:0 TX packets:187930 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:68712556 (68.7 MB) TX bytes:68712556 (68.7 MB) wlx503eaa7c4c9b Link encap:Ethernet HWaddr 50:3e:aa:7c:4c:9b inet addr:192.168.0.4 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::15de:9204:3015:b802/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:409882 errors:0 dropped:1902 overruns:0 frame:0 TX packets:308849 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:464826692 (464.8 MB) TX bytes:51670694 (51.6 MB)

We can see the network interface enp0s25 is not displayed in the list of active interfaces, after it was deactivated.

5. ifconfig command along with up option can be used to activate a network interface if it is not in active state. Use this command with root permissions. It is important to note that name of network interface must precede the command options.

$ sudo ifconfig enp0s25 up $ ifconfig enp0s25 Link encap:Ethernet HWaddr 7c:05:07:10:08:8d inet6 addr: fe80::5ba9:5ddd:a609:e410/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:4719 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:0 (0.0 B) TX bytes:963440 (963.4 KB) Interrupt:20 Memory:f7c00000-f7c20000 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 inet6 addr: ::1/128 Scope:Host UP LOOPBACK RUNNING MTU:65536 Metric:1 RX packets:190712 errors:0 dropped:0 overruns:0 frame:0 TX packets:190712 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:69933565 (69.9 MB) TX bytes:69933565 (69.9 MB) wlx503eaa7c4c9b Link encap:Ethernet HWaddr 50:3e:aa:7c:4c:9b inet addr:192.168.0.4 Bcast:192.168.0.255 Mask:255.255.255.0 inet6 addr: fe80::15de:9204:3015:b802/64 Scope:Link UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:410653 errors:0 dropped:1929 overruns:0 frame:0 TX packets:309651 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:1000 RX bytes:465020094 (465.0 MB) TX bytes:51915953 (51.9 MB)

6. ifconfig command can be used with an interface name (eth0) and ip address to assign an IP address to the specific interface. Use this command with root permissions.

$ sudo ifconfig eth0 192.168.72.228 $ ifconfig eth0: flags=4099 mtu 1500 inet 192.168.72.228 netmask 255.255.255.0 broadcast 192.168.72.255 ether 20:25:64:08:6a:a4 txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 device interrupt 20 memory 0xf7c00000-f7c20000 lo: flags=73 mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10 loop txqueuelen 1000 (Local Loopback) RX packets 16589 bytes 1698274 (1.6 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 16589 bytes 1698274 (1.6 MB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 wlan0: flags=4163 mtu 1500 inet 192.168.72.222 netmask 255.255.255.0 broadcast 192.168.72.255 inet6 fe80::fa1c:1e5f:feac:5280 prefixlen 64 scopeid 0x20 inet6 2409:4053:2105:527d:db24:166e:345d:d48a prefixlen 64 scopeid 0x0 inet6 2409:4053:2105:527d:653c:9f2d:750d:4528 prefixlen 64 scopeid 0x0 ether a4:2b:8c:5f:19:0b txqueuelen 1000 (Ethernet) RX packets 53256 bytes 15930912 (15.9 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 58487 bytes 12868848 (12.8 MB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

7. To assign an IP address, Netmask address and Broadcast address all at once, we can use the following command. Use this command with root permissions.

$ ifconfig eth0 192.168.72.144 netmask 255.255.255.0 broadcast 192.168.72.255 $ ifconfig eth0: flags=4099 mtu 1500 inet 192.168.72.144 netmask 255.255.255.0 broadcast 192.168.72.255 ether 20:25:64:08:6a:a4 txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 device interrupt 20 memory 0xf7c00000-f7c20000 lo: flags=73 mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10 loop txqueuelen 1000 (Local Loopback) RX packets 19543 bytes 2004727 (2.0 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 19543 bytes 2004727 (2.0 MB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 wlan0: flags=4163 mtu 1500 inet 192.168.72.222 netmask 255.255.255.0 broadcast 192.168.72.255 inet6 fe80::fa1c:1e5f:feac:5280 prefixlen 64 scopeid 0x20 inet6 2409:4053:2105:527d:db24:166e:345d:d48a prefixlen 64 scopeid 0x0 inet6 2409:4053:2105:527d:653c:9f2d:750d:4528 prefixlen 64 scopeid 0x0 ether a4:2b:8c:5f:19:0b txqueuelen 1000 (Ethernet) RX packets 62912 bytes 19006480 (19.0 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 69417 bytes 15159473 (15.1 MB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

8. Whenever a packet is received by a network card, it verifies if the packet belongs to itself. If not, it drops the packet normally, but in the promiscuous mode, it accept all the packets that flows through the network card. ifconfig command along with an interface name (eth0) and promisc argument enables promiscuous mode. In this mode the interface card will capture all the packets being broadcast. Use this command with root permissions. This is generally used by network sniffer programs like Wireshark to analyze broadcast packets.

$ ifconfig eth0 promisc $ ifconfig eth0: flags=4355 mtu 1000 inet 192.168.72.144 netmask 255.255.255.0 broadcast 192.168.72.255 ether aa:bb:cc:dd:ee:ff txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 device interrupt 20 memory 0xf7c00000-f7c20000 lo: flags=73 mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10 loop txqueuelen 1000 (Local Loopback) RX packets 22588 bytes 2330398 (2.3 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 22588 bytes 2330398 (2.3 MB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 wlan0: flags=4163 mtu 1500 inet 192.168.72.222 netmask 255.255.255.0 broadcast 192.168.72.255 inet6 fe80::fa1c:1e5f:feac:5280 prefixlen 64 scopeid 0x20 inet6 2409:4053:2105:527d:db24:166e:345d:d48a prefixlen 64 scopeid 0x0 inet6 2409:4053:2105:527d:653c:9f2d:750d:4528 prefixlen 64 scopeid 0x0 ether a4:2b:8c:5f:19:0b txqueuelen 1000 (Ethernet) RX packets 73307 bytes 22471053 (22.4 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 80986 bytes 17490208 (17.4 MB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

9. Use ifconfig command with an interface name (eth0) and -promisc argument to disable promiscuous mode.

$ ifconfig eth0 -promisc $ ifconfig eth0: flags=4099 mtu 1000 inet 192.168.72.144 netmask 255.255.255.0 broadcast 192.168.72.255 ether aa:bb:cc:dd:ee:ff txqueuelen 1000 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 device interrupt 20 memory 0xf7c00000-f7c20000 lo: flags=73 mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10 loop txqueuelen 1000 (Local Loopback) RX packets 22990 bytes 2375724 (2.3 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 22990 bytes 2375724 (2.3 MB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 wlan0: flags=4163 mtu 1500 inet 192.168.72.222 netmask 255.255.255.0 broadcast 192.168.72.255 inet6 fe80::fa1c:1e5f:feac:5280 prefixlen 64 scopeid 0x20 inet6 2409:4053:2105:527d:db24:166e:345d:d48a prefixlen 64 scopeid 0x0 inet6 2409:4053:2105:527d:653c:9f2d:750d:4528 prefixlen 64 scopeid 0x0 ether a4:2b:8c:5f:19:0b txqueuelen 1000 (Ethernet) RX packets 74842 bytes 23020724 (23.0 MB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 82714 bytes 17824215 (17.8 MB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 Print Page Previous Next Advertisements

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