关于网上lvs+keepalived的文章很多，但是多数都是DR模式的方案，对于 nat模式的并不多见，因此，在此写一份nat模式的文章，仅供分享也当笔记保存。
网络拓扑结构：
现在的Linux系统内核都是支持lvs的，所以我们直接可以用yum安装ipvsadm
yum 源的替换，将系统的yum源替换成163的yum源
[root@localhost ~]# cd /etc/yum.repos.d/
[root@localhost yum.repos.d]# ls
centos-163.repo rhel-source.repo.bak
[root@localhost yum.repos.d]# vim centos-163.repo
#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=updatesgpgcheck=1gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6 #additional packages that may be useful[extras]name=CentOS-6 - Extras - 163.combaseurl=http://mirrors.163.com/centos/6/extras/$basearch/#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=extrasgpgcheck=1gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6 #additional packages that extend functionality of existing packages[centosplus]name=CentOS-6 - Plus - 163.combaseurl=http://mirrors.163.com/centos/6/centosplus/$basearch/#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=centosplusgpgcheck=1enabled=0gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6 #contrib - packages by Centos Users[contrib]name=CentOS-6 - Contrib - 163.combaseurl=http://mirrors.163.com/centos/6/contrib/$basearch/#mirrorlist=http://mirrorlist.centos.org/?release=6&arch=$basearch&repo=contribgpgcheck=1enabled=0gpgkey=http://mirror.centos.org/centos/RPM-GPG-KEY-CentOS-6
LVS软件的安装
[root@localhost yum.repos.d]# yum install ipvsadm -y
开启路由转发功能
[root@localhost yum.repos.d]# vim /etc/sysctl.conf
将net.ipv4.ip_forward = 0改成net.ipv4.ip_forward = 1
使配置生效
[root@localhost yum.repos.d]# sysctl -p
net.ipv4.ip_forward = 1
net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.default.accept_source_route = 0
kernel.sysrq = 0
kernel.core_uses_pid = 1
net.ipv4.tcp_syncookies = 1
kernel.msgmnb = 65536
kernel.msgmax = 65536
kernel.shmmax = 68719476736
kernel.shmall = 4294967296
net.ipv4.ip_local_port_range = 1024 65000
关闭系统自带防火墙和selinux策略
[root@localhost yum.repos.d]# iptables -F
Chain INPUT (policy ACCEPT)
target prot opt source destination
Chain FORWARD (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
[root@localhost yum.repos.d]# iptables -t nat -F
Chain PREROUTING (policy ACCEPT)
target prot opt source destination
Chain POSTROUTING (policy ACCEPT)
target prot opt source destination
Chain OUTPUT (policy ACCEPT)
target prot opt source destination
[root@localhost yum.repos.d]# setenforce 0
keepalived安装和配置
由于nat模式的realserver的网关为负载服务器的IP。所以做主备的时候，网关也要能跟随外网VIP的切换一同切换，在这里，我们将定义一个vrrp组，一个inside_network,一个outside_network. inside_network的VIP作为RealServer网关地址，outside_network的VIP作为外网访问地址
xf keepalived-1.2.4.tar.gz
[root@localhostyum.repos.d]# yum install gcc* openssl* popt-devel libnl*
[root@localhostyum.repos.d]# cd keepalived-1.2.4
[root@localhost keepalived-1.2.4]# ./configure prefix=/usr/local/keepalived
[root@localhost keepalived-1.2.4]# make;make install
[root@localhost keepalived-1.2.4]# cd /usr/local/keepalived/etc/keepalived
[root@localhost keepalived-1.2.4]# cp keepalived.conf keepalived.conf_bak
[root@localhost keepalived-1.2.4]#cp /usr/local/keepalived/etc/sysconfig/keepalived /etc/sysconfig
[root@localhost keepalived]# vim /etc/keepalived/keepalived.conf
! Configuration File for keepalivedglobal_defs {notification_email {hehui0816@163.com #主备切换时候收邮件的地址,一行一个847616606@163.com }notification_email_from #指定邮件的来源smtp_server 127.0.0.1 #使用本地邮件服务器smtp_connect_timeout 30 #指定邮件连接超时时间router_id LVS_MASTER #指定router_id标识符 ，主备的可以相同，也可以不相同}vrrp_syncv_group SWJ { #定义一个虚拟路由组 group {inside_networkoutside_network}}vrrp_instance outside_network {state MASTER #设置主lvs负载为master ，备用的为BACKUPinterface eth0 #设置VIP的绑定网卡 track_interface { #定义额外的监听网卡，只要其中一个网卡出现故障就会发生主备切换# eth0eth1}lvs_sync_daemon_inteface eth0 #设置lvs监听网卡virtual_router_id 100 #设置虚拟路由ID号，同一组主备的ID号要一样priority 100 #设置优先级，MASTER的优先级要比BACKUP的高advert_int 1 #设置vrrp检测时间，默认为1Sauthentication { #设置认证信息，主备要一样auth_type PASSauth_pass 1111}virtual_ipaddress {10.204.172.2/26 #设置外网VIP}}vrrp_instance inside_network {state MASTERinterface eth1track_interface {eth0# eth1}lvs_sync_daemon_inteface eth0virtual_router_id 50priority 100advert_int 1authentication {auth_type PASSauth_pass 1111}virtual_ipaddress {192.168.1.21/24 #设置网关地址为内网VIP}}virtual_server 10.204.172.2 9912 { #设置策略 vip+端口 delay_loop 6lb_algo rr # 设置策略，在这里为轮询模式，也可以设置为wrr或其他lb_kind NAT #设置为NAT模式，DR模式换为DR即可nat_mask 255.255.255.192#persistence_timeout 50 # 此处注释，不然在50s里面访问的都是同一台后端服务器protocol TCPreal_server 192.168.1.32 9912 { #设置真实服务器IP+端口weight 1TCP_CHECK {connect_timeout 3nb_get_retry 3delay_before_retry 3connect_port 9912 #设置连接端口}}real_server 192.168.1.31 9912 {weight 1TCP_CHECK {connect_timeout 3nb_get_retry 3delay_before_retry 3connect_port 9912}}}
配置好了之后启动keepalived服务
[root@localhost ~]# /etc/init.d/keepalived restart
Stopping keepalived: [ OK ]Starting keepalived: [ OK ]查看主lvs的IP
查看备用lvs的IP
查看lvs负载：
查看日志
模拟主设备出现故障，ifdown eth0 或者将keepalived服务关闭
会发现VIP都会切换到备用负载上面去。
通过访问都能正常转发：