About ifconfig
The "ifconfig" command allows the operating system to setup network interfaces and allow the user to view information about the configured network interfaces.
Syntax
ifconfig [-L] [-m] interface [create] [address_family] [address[/prefixlength] [dest_address]] [parameters]
ifconfig interface destroy
ifconfig -a [-L] [-d] [-m] [-u] [address_family]
ifconfig -l [-d] [-u] [address_family]
ifconfig [-L] [-d] [-m] [-u] [-C]
address For the DARPA-Internet family, the address is either a host name present in the host name data base, or a DARPA Internet address expressed in the Internet standard ``dot notation''.
It is also possible to use the CIDR notation (also known as the slash notation) to include the netmask. That is, one can specify an address like 192.168.0.1/16.
addres_family Specify the address family which affects interpretation of the remaining parameters. Since an interface can receive transmissions in differing protocols with different naming schemes, specifying the address family is recommended. The address or protocol families currently supported are ``inet'', ``inet6'',
dest_address Specify the address of the correspondent on the other end of a point to point link.
interface This parameter is a string of the form ``name unit'', for example, ``en0''.
add Another name for the alias parameter. Introduced for compatibility with BSD/OS.
alias Establish an additional network address for this interface. This is sometimes useful when changing network numbers, and one wishes to accept packets addressed to the old interface. If the address is on the same subnet as the first network address for this interface, a netmask of 0xffffffff has to be specified.
-alias Remove the network address specified. This would be used if you incorrectly specified an alias, or it was no longer needed. If you have incorrectly set an NS address having the side effect of specifying the host portion, removing all NS addresses will allow you to respecify the host portion.
anycast (Inet6 only.) Specify that the address configured is an anycast address. Based on the current specification, only routers may configure anycast addresses. Anycast address will not be used as source address of any of outgoing IPv6 packets.
arp Enable the use of the Address Resolution Protocol in mapping between network level addresses and link level addresses (default). This is currently implemented for mapping between DARPA Internet addresses and IEEE 802 48-bit MAC addresses (Ethernet, FDDI, and Token Ring addresses).
-arp Disable the use of the Address Resolution Protocol
broadcast (Inet only.) Specify the address to use to represent broadcasts to the network. The default broadcast address is the address with a host part of all 1's.
debug Enable driver dependent debugging code; usually, this turns on extra console error logging.
-debug Disable driver dependent debugging code.
Linux下网卡命名规律：eth0，eth1.第一块以太网卡，第二块。lo为环回接口，它的IP地址固定为127.0.0.1，掩码8位。它代表你的机器本身。
1、ifconfig是查看网卡的信息。
ifconfig [Interface]
Interface是可选项，如果不加此项，则显示系统中所有网卡的信息。如果添加此选项则显示所指定的网卡信息
例如：ifconfig eth0
eth0 Link encap:Ethernet
|
我们可以看到
第一行：连接类型：Ethernet（以太网）HWaddr（硬件mac地址）
第二行：网卡的IP地址、子网、掩码
第三行：UP（代表网卡开启状态）RUNNING（代表网卡的网线被接上）MULTICAST（支持组播）MTU：1500（最大传输单元）：1500字节
第四、五行：接收、发送数据包情况统计
第七行：接收、发送数据字节数统计信息。
2、ifconfig 配置网卡
配置网卡的IP地址
ifconfig eth0 192.168.0.1 netmask 255.255.255.0
在eth0上配置上192.168.0.1 的IP地址及24位掩码。若想再在eth0上在配置一个192.168.1.1/24 的IP地址怎么办？用下面的命令
ifconfig eth0：0 192.168.1.1 netmask 255.255.255.0
这时再用ifconifg命令查看，就可以看到两个网卡的信息了，分别为：eth0和eth0：0.若还想再增加IP，那网卡的命名就接着是：eth0：1、eth0：2……想要几个就填几个。ok！
delete Another name for the -alias parameter.
down Mark an interface ``down''. When an interface is marked ``down'', the system will not attempt to transmit messages through that interface. If possible, the interface will be reset to disable reception as well. This action does not automatically disable routes using the interface.
ether Another name for the lladdr parameter.
lladdr addr Set the link-level address on an interface. This can be used to e.g. set a new MAC address on an ethernet interface, though the mechanism used is not ethernet-specific. The address addr is specified as a series of colon-separated hex digits. If the interface is already up when this option is used, it will be briefly brought down and then brought backup again in order to ensure that the receive filter in the underlying ethernet hardware is properly reprogrammed.
media type If the driver supports the media selection system, set the media type of the interface to type. Some interfaces support the mutually exclusive use of one of several different physical media connectors. For example, a 10Mb/s Ethernet interface might support the use of either AUI or twisted pair connectors. Setting the media type to ``10base5/AUI'' would change the currently active connector to the AUI port. Setting it to ``10baseT/UTP'' would activate twisted pair. Refer to the interfaces' driver specific documentation or man page for a complete list of the available types.
-mediaopt opts If the driver supports the media selection system, set the specified media options on the interface. The opts argument is a comma delimited list of options to apply to the interface. Refer to the interfaces' driver specific man page for a complete list of available options.
tunnel src_addr dest_addr (IP tunnel devices only.) Configure the physical source and destination address for IP tunnel interfaces. The arguments src_addr and dest_addr are interpreted as the outer source/destination for the encapsulating IPv4/IPv6 header.
deletetunnel Unconfigure the physical source and destination address for IP tunnel interfaces previously configured with tunnel.
create Create the specified network pseudo-device. If the interface is given without a unit number, try to create a new device with an arbitrary unit number. If creation of an arbitrary device is successful, the new device name is printed to standard output.
destroy Destroy the specified network pseudo-device.
配置网卡的硬件地址
ifconfig eth0 hw ether xx：xx：xx：xx：xx：xx
就将网卡的硬件地址更改了，此时你就可以骗过局域网内的IP地址邦定了。
将网卡禁用
ifconfig eth0 down
将网卡启用
ifconfig eth0 up
ifconfig 命令的功能很强大，还可以设置网卡的MTU，混杂模式等。就不一一介绍了，用时间可以自己研究一下。
注意：用ifconfig命令配置的网卡信息，在网卡重启后机器重启后，配置就不存在。要想将上述的配置信息永远的存的电脑里，那就要修改网卡的配置文件了。
plumb Another name for the create parameter. Included for Solaris compatibility.
unplumb Another name for the destroy parameter. Included for Solaris compatibility.
metric n Set the routing metric of the interface to n, default 0. The routing metric is used by the routing protocol. Higher metrics have the effect of making a route less favorable; metrics are counted as addition hops to the destination network or host.
mtu n Set the maximum transmission unit of the interface to n, default is interface specific. The MTU is used to limit the size of packets that are transmitted on an interface. Not all interfaces support setting the MTU, and some interfaces have range restrictions.
netmask mask (Inet only.) Specify how much of the address to reserve for subdividing networks into subnetworks. The mask includes the network part of the local address and the subnet part, which is taken from the host field of the address. The mask can be specified as a single hexadecimal number with a leading `0x', with a dot-notation Internet address, or with a pseudo-network name listed in the network table. The mask contains 1's for the bit positions in the 32-bit address which are to be used for the network and subnet parts, and 0's for the host part. The mask should contain at least the standard network portion, and the subnet field should be contiguous with the network portion. The netmask can also be specified in CIDR notation after the address. See the address option above for more information.
prefixlen len (Inet6 only.) Specify that len bits are reserved for subdividing networks into sub-networks. The len must be integer, and for syntactical reason it must be between 0 to 128. It is almost always 64 under the current IPv6 assignment rule. If the parameter is omitted, 64 is used.
remove Another name for the -alias parameter. Introduced for compatibility with BSD/OS.
link[0-2] Enable special processing of the link level of the interface. These three options are interface specific in actual effect, how- ever, they are in general used to select special modes of operation. An example of this is to enable SLIP compression, or to select the connector type for some Ethernet cards. Refer to the man page for the specific driver for more information.
-link[0-2] Disable special processing at the link level with the specified interface.
up Mark an interface ``up''. This may be used to enable an interface after an ``ifconfig down''. It happens automatically when setting the first address on an interface. If the interface was reset when previously marked down, the hardware will be re-initialized.
Examples
ifconfig eth0
View the network settings on the first Ethernet adapter installed in the computer.
ifconfig -a
Display into on all network interfaces on server, active or inactive.
ifconfig eth0 down
If eth0 exists would take it down causing it cannot send or receive any information.
ifconfig eth0 up
If eth0 exists and in the down state would return it back to the up state allowing to to send and receive information.
ifconfig eth0 192.168.1.102 netmask 255.255.255.0 broadcast 192.168.1.255
Assign eth0 with the above values for IP, netmask and broadcast address.