1.临时更改,即时生效.

[root@freebsd7]# ifconfig
le0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> metric 0 mtu 1500
        options=8<VLAN_MTU>
        ether 00:0c:29:21:2d:a6
        inet 192.168.1.106 netmask 0xffffff00 broadcast 192.168.1.255
        media: Ethernet autoselect
        status: active
plip0: flags=108810<POINTOPOINT,SIMPLEX,MULTICAST,NEEDSGIANT> metric 0 mtu 1500
lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> metric 0 mtu 16384
        inet6 fe80::1%lo0 prefixlen 64 scopeid 0x3
        inet6 ::1 prefixlen 128
        inet 127.0.0.1 netmask 0xff000000

Freebsd# ifconfig le0 10.0.0.123 netmask 255.255.255.0

这种方法即时生效，但是重启机器后，信息不保留。

2.永久保留.

打开/etc/rc.conf
加入或修改：ifconfig_网卡名称="inet x.x.x.x  netmask x.x.x.x"
之后 reboot 或 #sh /etc/rc

Freebsd# more /etc/rc.conf

# -- sysinstall generated deltas -- # Thu Oct 12 09:37:56 2006
# Created: Thu Oct 12 09:37:56 2006
# Enable network daemons for user convenience.
# Please make all changes to this file, not to /etc/defaults/rc.conf.
# This file now contains just the overrides from /etc/defaults/rc.conf.
defaultrouter="10.0.0.1"
hostname="Freebsd.rhel5.com"
ifconfig_lnc0="inet 10.0.0.123  netmask 255.255.255.0"
keymap="us.iso"
linux_enable="YES"
sshd_enable="YES"
Freebsd#
这种方法，信息永久保留，但是修改完需要重启机器。

如果要设置多IP地址可用别名方式作修改如下

ifconfig_lnc0="inet 10.0.0.199  netmask 255.255.255.0"
改为

ifconfig_lnc0_alias0="inet 10.0.0.198  netmask 255.255.255.0"
ifconfig_lnc0_alias1="inet 10.0.0.197  netmask 255.255.255.0"