linux：ip link 用法详解

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1. 描述

该命令用于管理和查看网络接口，link 表示 link layer 的意思，即链路层

2. 语法

ip link help

# 以下是输出：
Usage: ip link add [link DEV] [ name ] NAME
		    [ txqueuelen PACKETS ]
		    [ address LLADDR ]
		    [ broadcast LLADDR ]
		    [ mtu MTU ] [index IDX ]
		    [ numtxqueues QUEUE_COUNT ]
		    [ numrxqueues QUEUE_COUNT ]
		    type TYPE [ ARGS ]

	ip link delete { DEVICE | dev DEVICE | group DEVGROUP } type TYPE [ ARGS ]

	ip link set { DEVICE | dev DEVICE | group DEVGROUP }
			[ { up | down } ]
			[ type TYPE ARGS ]
		[ arp { on | off } ]
		[ dynamic { on | off } ]
		[ multicast { on | off } ]
		[ allmulticast { on | off } ]
		[ promisc { on | off } ]
		[ trailers { on | off } ]
		[ carrier { on | off } ]
		[ txqueuelen PACKETS ]
		[ name NEWNAME ]
		[ address LLADDR ]
		[ broadcast LLADDR ]
		[ mtu MTU ]
		[ netns { PID | NAME } ]
		[ link-netns NAME | link-netnsid ID ]
		[ alias NAME ]
		[ vf NUM [ mac LLADDR ]
			 [ vlan VLANID [ qos VLAN-QOS ] [ proto VLAN-PROTO ] ]
			 [ rate TXRATE ]
			 [ max_tx_rate TXRATE ]
			 [ min_tx_rate TXRATE ]
			 [ spoofchk { on | off} ]
			 [ query_rss { on | off} ]
			 [ state { auto | enable | disable} ]
			 [ trust { on | off} ]
			 [ node_guid EUI64 ]
			 [ port_guid EUI64 ] ]
		[ { xdp | xdpgeneric | xdpdrv | xdpoffload } { off |
			  object FILE [ section NAME ] [ verbose ] |
			  pinned FILE } ]
		[ master DEVICE ][ vrf NAME ]
		[ nomaster ]
		[ addrgenmode { eui64 | none | stable_secret | random } ]
		[ protodown { on | off } ]
		[ protodown_reason PREASON { on | off } ]
		[ gso_max_size BYTES ] | [ gso_max_segs PACKETS ]

	ip link show [ DEVICE | group GROUP ] [up] [master DEV] [vrf NAME] [type TYPE]

	ip link xstats type TYPE [ ARGS ]

	ip link afstats [ dev DEVICE ]
	ip link property add dev DEVICE [ altname NAME .. ]
	ip link property del dev DEVICE [ altname NAME .. ]

	ip link help [ TYPE ]

TYPE := { bareudp | bond | bond_slave | bridge | bridge_slave |
          dummy | erspan | geneve | gre | gretap | ifb |
          ip6erspan | ip6gre | ip6gretap | ip6tnl |
          ipip | ipoib | ipvlan | ipvtap |
          macsec | macvlan | macvtap |
          netdevsim | nlmon | rmnet | sit | team | team_slave |
          vcan | veth | vlan | vrf | vti | vxcan | vxlan | xfrm }

2.1 参数

ip link set DEVICE  { up | down | arp { on | off } | name NEWNAME | address LLADDR } 
可选的 option：
- dev DEVICE：指定要操作的设备名
- up and down：启动或停用该设备
- arp on or arp off：启用或禁用该设备的arp协议
- name NAME：修改指定设备的名称，建议不要在该接口处于运行状态或已分配IP地址时重命名
- address LLADDRESS：设置指定接口的MAC地址

ip [ -s | -h | -d ] link show [dev DEV] 
可选的 option：
  -s[tatistics]：将显示各网络接口上的流量统计信息；
  -h[uman-readable]：以人类可读的方式显式，即单位转换；
  -d[etails]：显示详细信息
  （选项说明可以通过ip help查看）

2.2 例子

停用 eth1网卡：
  ~ # ip link set eth1 down
启用 eth1网卡：
    ~ # ip link set eth1 up
等价于:
~ #  ifconfig eth1 down 或 ifconfig eth1 up

~ # ip -s -h -d  link show  dev eth0
2: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP mode DEFAULT group default qlen 1000
    link/ether 00:0c:29:2c:3c:e0 brd ff:ff:ff:ff:ff:ff promiscuity 0 minmtu 46 maxmtu 16110 addrgenmode none numtxqueues 1 numrxqueues 1 gso_max_size 65536 gso_max_segs 65535
    RX: bytes  packets  errors  dropped missed  mcast
    507M       1.47M    0       0       0       0
    TX: bytes  packets  errors  dropped carrier collsns
    370M       1.24M    0       0       0       0
~ #

字段含义：
BROADCAST：支持广播
MULTICAST：支持组播
UP：代表网卡开启状态；如果是关闭状态则不显示UP（重要）
LOWER_UP：代表网卡的网线被接上
mtu 1500：网络接口的最大传输单元(Maximum Transmission Unit )：1500字节。是包或帧的最大长度，一般以字节记。
qdisc：排队规则
state UNKNOWN ：
mode DEFAULT ：
group default ：
qlen 1000：
link/ether 00:0c:29:2c:3c:e0 表示物理网卡地址
brd ff:ff:ff:ff:ff:ff