Ifconfig指令詳細解析

1.測試環境:

[root@lvskeep ~]# cat

/etc/redhat-release

CentOS

release 5.4 (Final)

[root@lvskeep ~]# uname -r

2.6.18-164.el5

[root@lvskeep ~]# ifconfig #本機的網絡配置

eth0 Link encap:Ethernet HWaddr 00:0C:29:BC:7A:11

inet addr:10.0.0.30 Bcast:10.0.0.255 Mask:255.255.255.0

inet6 addr: fe80::20c:29ff:febc:7a11/64 Scope:Link

UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

RX packets:893 errors:0 dropped:0

overruns:0 frame:0

TX packets:447 errors:0 dropped:0 overruns:0

carrier:0

collisions:0 txqueuelen:1000

RX bytes:91733 (89.5 KiB) TX bytes:84456 (82.4 KiB)

Interrupt:185 Base address:0x1400

inet addr:192.168.0.30 Bcast:192.168.0.255 Mask:255.255.255.0

inet6 addr: fe80::20c:29ff:febc:7a1b/64 Scope:Link

RX packets:25 errors:0 dropped:0

TX packets:44 errors:0 dropped:0

overruns:0 carrier:0

RX bytes:6622 (6.4 KiB) TX bytes:7942 (7.7 KiB)

Interrupt:169 Base address:0x1480

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:16436 Metric:1

RX packets:16 errors:0 dropped:0

TX packets:16 errors:0 dropped:0

collisions:0 txqueuelen:0

RX bytes:1224 (1.1 KiB) TX bytes:1224 (1.1 KiB)

說明：

eth0 表示第一塊網卡，其中 HWaddr 表示網卡的實體位址，我們可以看到目前這

個網卡的實體位址(MAC位址）是 00:0C:29:BC:7A:1B ； inet addr 用來表示網卡

的IP位址，此網卡的 IP位址是 10.0.0.30，廣播位址，

Bcast:10.0.0.255，掩碼位址Mask:255.255.255.0

lo 是表示主機的回壞位址，這個一般是用來測試一個網絡程式，但又不想讓局域

網或外網的使用者能夠檢視，隻能在此台主機上運作和檢視所用的網絡接口。比如我

們把HTTPD伺服器的指定到回壞位址，在浏覽器輸入 127.0.0.1 就能看到你所架

WEB網站了。但隻是您能看得到，區域網路的其它主機或使用者無從知道；

2.通過man指令檢視系統自帶的幫助

[root@lvskeep ~]# man ifconfig

NAME

ifconfig - configure a network interface

SYNOPSIS #摘要，概要，大意

ifconfig [interface]

ifconfig interface [aftype] options |

address ...

DESCRIPTION

Ifconfig 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 only needed when

debugging or when system tuning is

needed.

If no arguments are given,

ifconfig displays the status of the currently active interfaces. If a single interface argument is given, it

displays the status of the given interface only; if a single -a argument is given, it displays the status of all

interfaces, even those that are down. Otherwise, it configures an interface.

Address

Families

If the first argument after the

interface name is recognized as the name of a supported address family,that

address family is used for decoding and displaying all protocol addresses. Currently supported address families include

inet (TCP/IP, default), inet6 (IPv6), ax25 (AMPR Packet Radio), ddp (Appletalk

Phase

2), ipx (Novell IPX) and netrom (AMPR Packet radio). All numbers supplied as parts in IPv4 dotted

decimal notation may be decimal, octal, or hexadecimal, as specified in the ISO

C standard (that is, a leading 0x or 0X implies hexadecimal; otherwise, a

leading implies octal; otherwise,the number is interpreted as decimal). Use of

hexamedial and octal numbers is not RFC-compliant and therefore its use is discouraged and may go away.

OPTIONS

Interface #e.g eth0、eth1

The name of the interface. This is usually a driver name followed by a

unit number, for example eth0 for the first Ethernet interface.

e.g

[root@lvskeep ~]# ifconfig

eth0

inet addr:10.0.0.30 Bcast:10.0.0.255 Mask:255.255.255.0

RX packets:673 errors:0 dropped:0 overruns:0 frame:0

TX packets:338 errors:0 dropped:0 overruns:0 carrier:0

RX bytes:68647 (67.0 KiB) TX

bytes:66442 (64.8 KiB)

up This flag causes the interface to be activated. It is implicitly specified if an address is assigned to the interface.

在虛拟機上執行ifconfig eth0 up指令，激活eth0

[root@lvskeep ~]# ifconfig eth0 up

[root@lvskeep ~]# ifconfig #驗證是否激活

RX packets:893 errors:0 dropped:0 overruns:0

frame:0

TX packets:447 errors:0 dropped:0

eth1 Link encap:Ethernet HWaddr 00:0C:29:BC:7A:1B

lo Link encap:Local Loopback

看到eth0已經成功激活

down This flag causes the

driver for this interface to be shut down.

SecureCRT軟體

eth0 down

結果：光标不停閃爍

直接在虛拟機裡操作

eth1 Link

encap:Ethernet HWaddr 00:0C:29:BC:7A:1B

inet

addr:192.168.0.30 Bcast:192.168.0.255 Mask:255.255.255.0

UP BROADCAST

RUNNING MULTICAST MTU:1500 Metric:1

RX packets:25

errors:0 dropped:0 overruns:0 frame:0

TX packets:44

errors:0 dropped:0 overruns:0 carrier:0

collisions:0

txqueuelen:1000

RX bytes:6622 (6.4

KiB) TX bytes:7942 (7.7 KiB)

Interrupt:169 Base

address:0x1480

lo Link encap:Local

Loopback

inet6 addr:

::1/128 Scope:Host

UP LOOPBACK

RUNNING MTU:16436 Metric:1

RX packets:16

TX packets:16

txqueuelen:0

RX bytes:1224 (1.1

KiB) TX bytes:1224 (1.1 KiB)

說明：執行ifconfig eth0 down指令後，網卡eth0就停掉了，不工作了，已經斷開了連接配接，而SecureCRT就是通過eth0連接配接的虛拟機，是以光标會一直閃爍；通過在虛拟機上執行ifconfig指令驗證,eth0确實停掉了。

[-]arp Enable or disable the use of the ARP protocol on this interface.

[root@lvskeep ~]# ifconfig eth0 –arp #關閉了ARP協定

執行完此指令後，SecureCRT和虛拟機斷開連接配接。關閉ARP，IP位址和MAC位址失去了對應關系，無法識别對應的主機。

[root@lvskeep ~]# ifconfig eth0 arp #開啟ARP協定

再次連接配接正常 arp 指令（附錄一）

[-]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 #指定在計算資料包的轉送次數時，所要加上的數目

This parameter sets the interface

metric.

mtu

N This parameter sets the Maximum

Transfer Unit (MTU) of an interface.

#設定網絡裝置的MTU

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

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.

[root@lvskeep ~]# ifconfig eth1

192.168.0.30 netmask 255.255.0.0 #子網路遮罩

inet addr:192.168.0.30 Bcast:192.168.255.255 Mask:255.255.0.0

UP BROADCAST RUNNING NOARP

MULTICAST MTU:1500 Metric:1

TX packets:54 errors:0 dropped:0

RX bytes:6622 (6.4 KiB) TX bytes:11144 (10.8 KiB)

注意：netmask不能大寫

add

addr/prefixlen

Add an IPv6 address to an

interface. #設定網絡裝置IPv6的IP位址

del addr/prefixlen

Remove an IPv6 address from an

interface.# 删除網絡裝置IPv6的IP位址

tunnel

aa.bb.cc.dd

Create a new SIT (IPv6-in-IPv4)

device, tunnelling to the given destination. #建立IPv4與IPv6之間的隧道通信位址

irq

Set the interrupt line used by this device. Not all devices can dynamically change their

IRQ setting.# 置網絡裝置的IRQ

io_addr addr #設定網絡裝置的I/O位址

Set the start address in I/O

space for this device.

mem_start

addr #設定網絡裝置在主記憶體所占用的起始位址

Set the start address for shared

memory used by this device. Only a few

devices need this.

media

type #設定網絡裝置的媒介類型

Set the physical port or medium

type to be used by the device. Not all

devices can change this setting, and those that can vary in what values they support. Typical values for type are 10base2 (thin

Ethernet), 10baseT (twisted-pair 10Mbps Ethernet), AUI (external transceiver)and so on. The special medium

type of auto can be used to tell the driver to auto-sense the media.Again, not

all drivers can do this.

[-]broadcast [addr] #将要送往指定位址的資料包當成廣播資料包來處理

If the address argument is given, set

the protocol broadcast address for this interface.Other-wise, set (or clear)

the IFF_BROADCAST flag for the interface.

[-]pointopoint

[addr] # 與指定位址的網絡裝置建立直接連線，此模式具有保密功能。

This keyword enables the point-to-point mode

of an interface, meaning that it is a direct 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 IFF_POINTOPOINT flag for the interface.

hw

class address

Set the hardware address of this

interface, if the device driver supports this operation. The

multicast

Set the multicast flag on the interface. This should not

normally be needed as the drivers set the flag correctly themselves.

address

The IP address to be assigned to

this interface.

txqueuelen

length

Set the length of the transmit

queue of the device. It is useful to set this to small values for slower devices with a high latency

(modem links, ISDN) to prevent fast bulk transfers from dis-

turbing interactive traffic like

telnet too much.

NOTES

Since kernel release 2.2 there are no

explicit interface statistics for alias interfaces anymore. The statistics printed for the original address are shared with all alias addresses on the same

device. If you want per-address statistics

you should add explicit accounting rules for the address using the ipchains(8) command.

Interrupt problems with Ethernet device drivers fail with EAGAIN. See

http://www.scyld.com/expert/irq-conflict.html for more information.

FILES

/proc/net/socket

/proc/net/dev

/proc/net/if_inet6

BUGS

While appletalk DDP and IPX addresses

will be displayed they cannot be altered by this command.

SEE

ALSO

route(8), netstat(8), arp(8), rarp(8),

ipchains(8)

AUTHORS

Fred N. van Kempen,

Alan Cox,

Phil Blundell,

Andi Kleen

net-tools 14 August 2000 IFCONFIG(8)

執行個體：

1.如果我們想知道主機所有網絡接口的情況，請用下面的指令：

[root@lvskeep

~]# ifconfig -a

UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1

RX packets:2974 errors:0 dropped:0 overruns:0 frame:0

TX packets:1342 errors:0 dropped:0 overruns:0 carrier:0

RX bytes:280167 (273.6 KiB) TX

bytes:214214 (209.1 KiB)

UP BROADCAST RUNNING NOARP MULTICAST MTU:1500 Metric:1

RX packets:25 errors:0 dropped:0 overruns:0 frame:0

TX packets:66 errors:0 dropped:0 overruns:0 carrier:0

RX bytes:6622 (6.4 KiB) TX bytes:14376 (14.0 KiB)

RX packets:108 errors:0 dropped:0 overruns:0 frame:0

TX packets:108 errors:0 dropped:0 overruns:0 carrier:0

RX bytes:11816 (11.5 KiB) TX

bytes:11816 (11.5 KiB)

sit0 Link encap:IPv6-in-IPv4

NOARP MTU:1480 Metric:1

RX packets:0 errors:0 dropped:0 overruns:0 frame:0

TX packets:0 errors:0 dropped:0 overruns:0 carrier:0

RX bytes:0 (0.0 b) TX bytes:0

(0.0 b)

2.如果我們想檢視某個端口，比如我們想檢視eth1 的狀态，就可以用下面的方法

~]# ifconfig eth1

RX bytes:6622 (6.4 KiB) TX

bytes:14376 (14.0 KiB)

ifconfig 配置網絡端口的方法

ifconfig 工具配置網絡接口的方法是通過指令的參數來達到目的的

ifconfig 網絡端口 IP位址 hw MAC位址 netmask 掩碼位址

broadcast 廣播位址 [up/down]

3.用ifconfig 來調試 eth1網卡的位址

eth1 down

eth1 192.168.1.30 broadcast 192.168.1.255 netmask 255.255.255.0

eth1 up

eth1

inet addr:192.168.1.30 Bcast:192.168.1.255 Mask:255.255.255.0

TX packets:91 errors:0 dropped:0 overruns:0 carrier:0

bytes:21736 (21.2 KiB)

第一行：ifconfig eth0 down 表示如果eth0是激活的，就把它DOWN掉。此指令等同于 ifdown eth0；

第二行：用ifconfig 來配置 eth0的IP位址、廣播位址和網絡掩碼；

第三行：用ifconfig eth0 up 來激活eth0 ；此指令等同于 ifup eth0

第四行：用 ifconfig eth0 來檢視 eth0的狀态；

也可以用直接在指令IP位址、網絡掩碼、廣播位址的同時，激活網卡；要加up參數

[root@lvskeep ~]# ifconfig eth1 192.168.1.30

broadcast 192.168.1.255 netmask 255.255.255.0 up

4.設定網卡eth1的IP位址、網絡掩碼、廣播位址，實體位址并且激活它

[root@lvskeep ~]# ifconfig

eth1 192.168.0.30 hw ether 00:0C:29:BC:7A:11 broadcast 192.168.0.255 netmask 255.255.255.0 up

SIOCSIFHWADDR: Device or

resource busy

先停掉然後再改，MAC位址最好别改，很容易出錯，個人了解。

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