命令格式：
ifconfig [-v] [-a] [-s] [interface]
ifconfig [-v] interface [aftype] options | address ...
配置网络接口
选项：
-a 显示当前所有可获取的网络接口信息，包括状态为down的接口
-s 已短列表方式显示（类似 netstat -i)
-v be more verbose for some error conditions
interface
网络接口名称
up This flag causes the interface to be activated. It is implicitly specified if an address is
assigned to the interface.
down This flag causes the driver for this interface to be shut down.
[-]arp 打开或关闭指定接口上的ARP协议。前面加上减号用于关闭该选项。
[-]promisc
关闭或启动指定网络设备的混杂模式（promiscuous mode）。如果启动混杂模式，该网络接口将接收网络上的所有数据包。
前面加上减号用于关闭该选项。
[-]allmulti
Enable or disable all-multicast mode. If selected, all multicast packets on the network will
be received by the interface.
mtu N This parameter sets the Maximum Transfer Unit (MTU) of an interface.
dstaddr addr
Set the remote IP address for a point-to-point link (such as PPP). This keyword is now obso‐
lete; use the pointopoint keyword instead.
netmask addr
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.
add addr/prefixlen
Add an IPv6 address to an interface.
del addr/prefixlen
Remove an IPv6 address from an interface.
tunnel ::aa.bb.cc.dd
Create a new SIT (IPv6-in-IPv4) device, tunnelling to the given destination.
irq addr
Set the interrupt line used by this device. Not all devices can dynamically change their IRQ
setting.
io_addr addr
Set the start address in I/O space for this device.
mem_start addr
Set the start address for shared memory used by this device. Only a few devices need this.
media type
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]
If the address argument is given, set the protocol broadcast address for this interface. Oth‐
erwise, set (or clear) the IFF_BROADCAST flag for the interface.
[-]pointopoint [addr]
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
keyword must be followed by the name of the hardware class and the printable ASCII equivalent
of the hardware address. Hardware classes currently supported include ether (Ethernet), ax25
(AMPR AX.25), ARCnet and netrom (AMPR NET/ROM).
multicast
Set the multicast flag on the interface. This should not normally be needed as the drivers set
the flag correctly themselves.
address
给接口指定的IP地址.
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
disturbing interactive traffic like telnet too much.
应用举例：
# ifconfig