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选题[tech]: 20210125 Why you need to drop ifconfig for ip
sources/tech/20210125 Why you need to drop ifconfig for ip.md
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sources/tech/20210125 Why you need to drop ifconfig for ip.md
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[#]: collector: (lujun9972)
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[#]: translator: ( )
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[#]: reviewer: ( )
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[#]: publisher: ( )
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[#]: url: ( )
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[#]: subject: (Why you need to drop ifconfig for ip)
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[#]: via: (https://opensource.com/article/21/1/ifconfig-ip-linux)
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[#]: author: (Rajan Bhardwaj https://opensource.com/users/rajabhar)
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Why you need to drop ifconfig for ip
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======
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Start using the modern method for configuring a Linux network interface.
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![Tips and gears turning][1]
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For a long time, the `ifconfig` command was the default method for configuring a network interface. It served Linux users well, but networking is complex, and the commands to configure it must be robust. The `ip` command is the new default networking command for modern systems, and in this article, I'll show you how to use it.
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The `ip` command is functionally organized on two layers of the [OSI networking stack][2]: Layer 2 (data link layer) and Layer 3 (network or IP layer). It does all the work in the old `net-tools` package.
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### Installing ip
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The `ip` command is included in the `iproute2util` package. It's probably already included in your Linux distribution. If it's not, you can install it from your distro's software repository.
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### Comparing ipconfig and ip usage
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The `ip` and `ipconfic` commands can be used to configure a network interface, but they do things differently. I'll compare how to do common tasks with the old (`ipconfig`) and new (`ip`) commands.
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#### View network interface and IP address
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If you want to see the IP address of a host or view network interface information, the old `ifconfig` command, with no arguments, provides a good summary:
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```
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$ ifconfig
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eth0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
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ether bc:ee:7b:5e:7d:d8 txqueuelen 1000 (Ethernet)
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RX packets 0 bytes 0 (0.0 B)
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RX errors 0 dropped 0 overruns 0 frame 0
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TX packets 0 bytes 0 (0.0 B)
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TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
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lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536
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inet 127.0.0.1 netmask 255.0.0.0
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inet6 ::1 prefixlen 128 scopeid 0x10<host>
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loop txqueuelen 1000 (Local Loopback)
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RX packets 41 bytes 5551 (5.4 KiB)
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RX errors 0 dropped 0 overruns 0 frame 0
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TX packets 41 bytes 5551 (5.4 KiB)
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TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
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wlan0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
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inet 10.1.1.6 netmask 255.255.255.224 broadcast 10.1.1.31
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inet6 fdb4:f58e:49f:4900:d46d:146b:b16:7212 prefixlen 64 scopeid 0x0<global>
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inet6 fe80::8eb3:4bc0:7cbb:59e8 prefixlen 64 scopeid 0x20<link>
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ether 08:71:90:81:1e:b5 txqueuelen 1000 (Ethernet)
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RX packets 569459 bytes 779147444 (743.0 MiB)
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RX errors 0 dropped 0 overruns 0 frame 0
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TX packets 302882 bytes 38131213 (36.3 MiB)
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TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
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```
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The new `ip` command provides similar results, but the command is `ip address show`, or just `ip a` for short:
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```
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$ ip a
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1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
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link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
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inet 127.0.0.1/8 scope host lo
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valid_lft forever preferred_lft forever
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inet6 ::1/128 scope host
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valid_lft forever preferred_lft forever
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2: eth0: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
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link/ether bc:ee:7b:5e:7d:d8 brd ff:ff:ff:ff:ff:ff
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3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP group default qlen 1000
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link/ether 08:71:90:81:1e:b5 brd ff:ff:ff:ff:ff:ff
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inet 10.1.1.6/27 brd 10.1.1.31 scope global dynamic wlan0
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valid_lft 83490sec preferred_lft 83490sec
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inet6 fdb4:f58e:49f:4900:d46d:146b:b16:7212/64 scope global noprefixroute dynamic
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valid_lft 6909sec preferred_lft 3309sec
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inet6 fe80::8eb3:4bc0:7cbb:59e8/64 scope link
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valid_lft forever preferred_lft forever
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```
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#### Add IP address
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To add an IP address to an interface with `ifconfig`, the command is:
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```
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`$ ifconfig eth0 add 192.9.203.21`
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```
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The command is similar for `ip`:
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```
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`$ ip address add 192.9.203.21 dev eth0`
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```
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Subcommands in `ip` can be shortened, so this command is equally valid:
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```
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`$ ip addr add 192.9.203.21 dev eth0`
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```
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You can make it even shorter:
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```
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`$ ip a add 192.9.203.21 dev eth0`
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```
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#### Remove an IP address
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The inverse of adding an IP address is to remove one.
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With `ifconfig`, the syntax is:
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```
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`$ ifconfig eth0 del 192.9.203.21`
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```
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The `ip` command syntax is:
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```
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`$ ip a del 192.9.203.21 dev eth0`
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```
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#### Enable or disable multicast
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Enabling (or disabling) [multicast][3] on an interface with `ifconfig` happens with the `multicast` argument:
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```
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`# ifconfig eth0 multicast`
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```
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With `ip`, use the `set` subcommand with the device (`dev`) and a Boolean or toggle `multicast` option:
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```
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`# ip link set dev eth0 multicast on`
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```
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#### Enable or disable a network
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Every sysadmin is familiar with the old "turn it off and then on again" trick to fix a problem. In terms of networking interfaces, that translates to bringing a network up or down.
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The `ifconfig` command does this with the `up` or `down` keywords:
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```
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`# ifconfig eth0 up`
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```
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Or you could use a dedicated command:
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```
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`# ifup eth0`
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```
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The `ip` command uses the `set` subcommand to set the interface to an `up` or `down` state:
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```
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`# ip link set eth0 up`
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```
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#### Enable or disable the Address Resolution Protocol (ARP)
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With `ifconfig`, you enable ARP by declaring it:
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```
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`# ifconfig eth0 arp`
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```
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With `ip`, you _set_ the `arp` property as `on` or `off`:
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```
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`# ip link set dev eth0 arp on`
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```
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### Pros and cons of ip and ipconfig
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The `ip` command is more versatile and technically more efficient than `ifconfig` because it uses `Netlink` sockets rather than `ioctl` system calls.
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The `ip` command may appear more verbose and more complex than `ifconfig`, but that's one reason it's more versatile. Once you start using it, you'll get a feel for its internal logic (for instance, using `set` instead of a seemingly arbitrary mix of declarations or settings).
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Ultimately, `ifconfig` is outdated (for instance, it lacks full support for network namespaces), and `ip` is designed for the modern network. Try it out, learn it, use it. You'll be glad you did!
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--------------------------------------------------------------------------------
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via: https://opensource.com/article/21/1/ifconfig-ip-linux
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作者：[Rajan Bhardwaj][a]
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选题：[lujun9972][b]
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译者：[译者ID](https://github.com/译者ID)
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校对：[校对者ID](https://github.com/校对者ID)
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本文由 [LCTT](https://github.com/LCTT/TranslateProject) 原创编译，[Linux中国](https://linux.cn/) 荣誉推出
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[a]: https://opensource.com/users/rajabhar
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[b]: https://github.com/lujun9972
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[1]: https://opensource.com/sites/default/files/styles/image-full-size/public/lead-images/gears_devops_learn_troubleshooting_lightbulb_tips_520.png?itok=HcN38NOk (Tips and gears turning)
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[2]: https://en.wikipedia.org/wiki/OSI_model
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[3]: https://en.wikipedia.org/wiki/Multicast
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