安装ucarp（支持IP的动态替换）
libpcap (http://www.tcpdump.org/) must be installed on your system, with development files (headers).
http://download.pureftpd.org/pub/ucarp/README
ucarp的下载页说得很明白，要先安装libpcap包，好吧，先安装它吧。
下载libpcap的最新版，也可以在我的资源中找到。
假设你的版本是：libpcap-1.2.1.tar.gz
tar -zxf libpcap-1.2.1.tar.gz
cd libpcap-1.2.1
./configure
如安装过程中有如下提示：
configure: error: Your operating system's lex is insufficient to compile libpcap. flex is a lex replacement that has many advantages, including being able to compile libpcap. For more information, see http://www.gnu.org/software/flex/flex.html .就是说flex不完全，好吧，我们再根据提示去下载flex
http://sourceforge.net/projects/flex/?source=dlp
我下载的版本是：flex-2.5.37.tar.bz2
如果你linux没安装bz2的解圧程序，那先安装
http://bzip.org/downloads.html
我下载的版本是：
tar -zxf bzip2-1.0.6.tar.gz
cd bzip2-1.0.6
sudo make install安装完成之后，解压 flex-2.5.37.tar.bz2
tar -jxvf flex-2.5.37.tar.bz2
cd flex-2.5.37
./configure
出现如下错误
checking for m4 that supports -P... configure: error: could not find m4 that supports -P
去 http://ftp.gnu.org/gnu/m4/下载m4的安装包
注意要下载最新版。
安装好m4之后，安装flex成功
再安装libpcap
还缺少bison包，再下载bison
http://ftp.gnu.org/gnu/bison/所有的这些都安装好，libpcap总算安装好。
下载ucarp包
http://download.pureftpd.org/pub/ucarp/
我的版本是1.5.2
安装，应该没什么问题了。
执行
/usr/local/sbin/ucarp提示错误：
/usr/local/sbin/ucarp: error while loading shared libraries: libpcap.so.1: cannot open shared object file: No such file or directory
经过验证，发现libpcap.so.1在/usr/local/lib下
执行以下命令
sudo cp /usr/local/lib/libpcap.so.1 /usr/lib
再执行ucarp
搞定
ucarp 1.5.2 - Mar 20 2013
--interface=<if> (-i <if>): bind interface <if>
--srcip=<ip> (-s <ip>): source (real) IP address of that host
--vhid=<id> (-v <id>): virtual IP identifier (1-255)
--pass=<pass> (-p <pass>): password
--passfile=<file> (-o <file>): read password from file
--preempt (-P): becomes a master as soon as possible
--neutral (-n): don't run downscript at start if backup
--addr=<ip> (-a <ip>): virtual shared IP address
--help (-h): summary of command-line options
--advbase=<seconds> (-b <seconds>): advertisement frequency
--advskew=<skew> (-k <skew>): advertisement skew (0-255)
--upscript=<file> (-u <file>): run <file> to become a master
--downscript=<file> (-d <file>): run <file> to become a backup
--deadratio=<ratio> (-r <ratio>): ratio to consider a host as dead
--shutdown (-z): call shutdown script at exit
--daemonize (-B): run in background
--ignoreifstate (-S): ignore interface state (down, no carrier)
--nomcast (-M): use broadcast (instead of multicast) advertisements
--facility=<facility> (-f): set syslog facility (default=daemon)
--xparam=<value> (-x): extra parameter to send to up/down scripts
Sample usage:
Manage the 10.1.1.252 shared virtual address on interface eth0, with
1 as a virtual address idenfitier, mypassword as a password, and
10.1.1.1 as a real permanent address for this host.
Call /etc/vip-up.sh when the host becomes a master, and
/etc/vip-down.sh when the virtual IP address has to be disabled.
ucarp --interface=eth0 --srcip=10.1.1.1 --vhid=1 --pass=mypassword \
--addr=10.1.1.252 \
--upscript=/etc/vip-up.sh --downscript=/etc/vip-down.sh
Please report bugs to bugs at ucarp dot org.