C++后端开发进阶
第5章网络通信故障排查常用命令

5.1 ifconfig

ifconfig 是我们查看当前系统的网卡和 ip 地址信息的最常用命令。如果你的机器上还没安装 ifconfig 命令，可以使用如下命令安装：

yum install net-tools

安装成功以后，我们就可以使用 ifconfig 查看机器网卡信息了：

[root@localhost ~]# ifconfig
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.206.140  netmask 255.255.255.0  broadcast 192.168.206.255
        inet6 fe80::1599:dcc4:b3e8:7fce  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:ee:01:80  txqueuelen 1000  (Ethernet)
        RX packets 1005  bytes 77224 (75.4 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 349  bytes 47206 (46.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 4  bytes 352 (352.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 4  bytes 352 (352.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

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上述输出显示了本机当前激活的网卡列表，以及每个激活的网卡（网络设备）的 ipv4、ipv6 地址、子网掩码、广播地址等信息，这里一共两个网卡，分别是 ens33 和 lo。

我们可以使用 -s 选项显示网卡信息的精简列表：

[root@localhost ~]# ifconfig -s
Iface      MTU    RX-OK RX-ERR RX-DRP RX-OVR    TX-OK TX-ERR TX-DRP TX-OVR Flg
ens33            1500     1086      0      0 0           379      0      0      0 BMRU
lo              65536        4      0      0 0             4      0      0      0 LRU

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默认情况下，ifconfig 命令只会显示激活的网卡信息，可以使用 -a 选项显示所有的（包括未激活）的网卡信息。

使用 ifconfig up 命令激活某个网卡，使用 ifconfig down 命令禁用某个网卡，这两个命令的用法如下：

ifconfig 网卡名 up
ifconfig 网卡名 down

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我们来演示一下这两个命令的用法：

[root@localhost ~]# ifconfig
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.206.140  netmask 255.255.255.0  broadcast 192.168.206.255
        inet6 fe80::1599:dcc4:b3e8:7fce  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:ee:01:80  txqueuelen 1000  (Ethernet)
        RX packets 1398  bytes 114269 (111.5 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 601  bytes 97657 (95.3 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 12  bytes 1056 (1.0 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12  bytes 1056 (1.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

## 禁用网卡 lo 后默认只能看到一个网卡信息
[root@localhost ~]# ifconfig lo down
[root@localhost ~]# ifconfig 
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.206.140  netmask 255.255.255.0  broadcast 192.168.206.255
        inet6 fe80::1599:dcc4:b3e8:7fce  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:ee:01:80  txqueuelen 1000  (Ethernet)
        RX packets 1510  bytes 123232 (120.3 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 657  bytes 104751 (102.2 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

[root@localhost ~]# ifconfig -a
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.206.140  netmask 255.255.255.0  broadcast 192.168.206.255
        inet6 fe80::1599:dcc4:b3e8:7fce  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:ee:01:80  txqueuelen 1000  (Ethernet)
        RX packets 1543  bytes 125948 (122.9 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 675  bytes 107251 (104.7 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=8<LOOPBACK>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 12  bytes 1056 (1.0 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12  bytes 1056 (1.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
## 再次启用网卡 lo
[root@localhost ~]# ifconfig lo up
[root@localhost ~]# ifconfig 
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.206.140  netmask 255.255.255.0  broadcast 192.168.206.255
        inet6 fe80::1599:dcc4:b3e8:7fce  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:ee:01:80  txqueuelen 1000  (Ethernet)
        RX packets 1615  bytes 131924 (128.8 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 715  bytes 112423 (109.7 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 12  bytes 1056 (1.0 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12  bytes 1056 (1.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

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ifconfig 还可以将一个 ip 地址绑定到某个网卡上，或将一个 ip 地址从某个网卡上解绑，使用如下命令：

# 将指定ip地址绑定到某个网卡
ifconfig 网卡名 add ip地址
# 从某个网卡解绑指定ip地址
ifconfig 网卡名 del ip地址

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演示上述两个操作如下：

[root@localhost ~]# ifconfig 
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.206.140  netmask 255.255.255.0  broadcast 192.168.206.255
        inet6 fe80::1599:dcc4:b3e8:7fce  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:ee:01:80  txqueuelen 1000  (Ethernet)
        RX packets 1615  bytes 131924 (128.8 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 715  bytes 112423 (109.7 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 12  bytes 1056 (1.0 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12  bytes 1056 (1.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

[root@localhost ~]# ifconfig ens33 add 192.168.206.150
[root@localhost ~]# ifconfig
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.206.140  netmask 255.255.255.0  broadcast 192.168.206.255
        inet6 fe80::1599:dcc4:b3e8:7fce  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:ee:01:80  txqueuelen 1000  (Ethernet)
        RX packets 1804  bytes 145940 (142.5 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 781  bytes 119581 (116.7 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

ens33:0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.206.150  netmask 255.255.255.0  broadcast 192.168.206.255
        ether 00:0c:29:ee:01:80  txqueuelen 1000  (Ethernet)

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 12  bytes 1056 (1.0 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 12  bytes 1056 (1.0 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

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上述操作中，网卡 ens33 开始绑定了 ip 地址 192.168.206.140，我们使用 ifconfig add 命令绑定了一个新的 ip ：192.168.206.150，现在我们可以使用这个新的 ip 地址来访问原来的网络了。

同理，如果要解绑这个 ip 地址，可以按如下操作：

[root@localhost ~]# ifconfig ens33 del 192.168.206.150
[root@localhost ~]# ifconfig -a
ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.206.140  netmask 255.255.255.0  broadcast 192.168.206.255
        inet6 fe80::1599:dcc4:b3e8:7fce  prefixlen 64  scopeid 0x20<link>
        ether 00:0c:29:ee:01:80  txqueuelen 1000  (Ethernet)
        RX packets 2127  bytes 172321 (168.2 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 953  bytes 139954 (136.6 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 18  bytes 1560 (1.5 KiB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 18  bytes 1560 (1.5 KiB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

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在 Windows 上与 ifconfig 相对应的命令是 ipconfig，如在 Windows 上查看所有网卡信息可以使用 ipconfig /all。

上次更新: 2025/04/01, 20:53:14

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