在之前一篇使用nginx搭建高可用的解决方案的时候，很多同学会问，如果nginx挂掉怎么办，比如下面这张图：
你可以清楚的看到，如果192.168.2.100这台机器挂掉了，那么整个集群就下线了，这个问题该怎么解决呢？？？ 简单的想想确实不大好处理，因为你
的webBrowser总得要访问一个ip地址，对吧。。这个问题怎么破呢？
一：问题分析
如果你有一些网络底子的话，就会明白，你给一个不在本网段的机器发送请求的话，这个请求会先经过你的网关IP，然后通过网关IP传给对方的网关IP，然
后网关IP会将请求转给它所在局域网的主机，当然我的网关IP和对方的网关IP之间可能有很多跳的路由地址，大概的流程就是下面这样：
如果你不信的话，可以用tracert 看看你到www.ctrip.com的路由总过程。
从上图中可以看到，从我当前主机到ctrip.com一共有20跳，第一条是192.168.2.1，这个就是我的路由器IP，也就是我的网关IP。
二：虚拟路由冗余协议
好了，说了这么多有什么用呢？其实大家仔细观察这张图，你会想我能不能在网关IP上做一些手脚呢？ 可喜的是如今的路由器基本上都支持一个叫做
VRRP（虚拟路由冗余协议），这一协议的作用你可以理解成把网关IP虚拟化成一个网关IP集群，就好像兽族剑圣的镜像技能，这里面有master，也有slave，
然后局域网内的主机设置的都是虚拟的masterIP（VIP），刚好keepealived就是一个实现VRRP的一款应用程序，你需要，我专业，大家就这样走到一块了。
三：keepalived搭建一览
1. 下载：从官网上找到当前最新的版本1.4.2。http://www.keepalived.org/software/keepalived-1.4.2.tar.gz。
配置机器： 192.168.23.156 【centos】
192.168.23.157 【centos】
1 [root@localhost app]# wget http://www.keepalived.org/software/keepalived-1.4.2.tar.gz 2 --2018-03-10 04:04:06-- http://www.keepalived.org/software/keepalived-1.4.2.tar.gz 3 Resolving www.keepalived.org (www.keepalived.org)... 37.59.63.157, 2001:41d0:8:7a9d::1 4 Connecting to www.keepalived.org (www.keepalived.org)|37.59.63.157|:80... connected. 5 HTTP request sent, awaiting response... 200 OK 6 Length: 738096 (721K) [application/x-gzip] 7 Saving to: ‘keepalived-1.4.2.tar.gz’ 8 9 100%[==================================================================>] 738,096 5.24KB/s in 4m 44s
2. 然后把相关依赖装起来：yum install -y openssl openssl-devel。
1 [root@localhost app]# yum install -y openssl openssl-devel 2 Loaded plugins: fastestmirror, langpacks 3 Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=os&infra=stock error was 4 14: curl#52 - "Empty reply from server" 5 base | 3.6 kB 00:00:00 6 epel/x86_64/metalink | 7.8 kB 00:00:00 7 Could not retrieve mirrorlist http://mirrorlist.centos.org/?release=7&arch=x86_64&repo=extras&infra=stock error was 8 14: curl#52 - "Empty reply from server" 9 extras | 3.4 kB 00:00:00 10 updates | 3.4 kB 00:00:00 11 updates/7/x86_64/primary_db | 6.9 MB 00:01:10
3. 接下来继续解压，最后安装三板斧： ./configure --prefix=/usr/app/keepalived && make && make install。
[root@localhost app]# tar -zxvf keepalived-1.4.2.tar.gz [root@localhost app]# ls keepalived-1.4.2 keepalived-1.4.2.tar.gz [root@localhost app]# cd keepalived-1.4.2 [root@localhost keepalived-1.4.2]# ls aclocal.m4 bin_install configure COPYING genhash keepalived Makefile.am README.md ar-lib ChangeLog configure.ac depcomp INSTALL keepalived.spec.in Makefile.in snap AUTHOR compile CONTRIBUTORS doc install-sh lib missing TODO [root@localhost keepalived-1.4.2]#
[root@localhost keepalived-1.4.2]# ./configure --prefix=/usr/app/keepalived && make && make install
安装好了之后，你就会看到如下的内容，那就恭喜你，安装成功了。
Keepalived configuration ------------------------ Keepalived version : 1.4.2 Compiler : gcc Preprocessor flags : Compiler flags : -Wall -Wunused -Wstrict-prototypes -Wextra -g -O2 -fPIE -D_GNU_SOURCE Linker flags : -pie Extra Lib : -lcrypto -lssl Use IPVS Framework : Yes IPVS use libnl : No IPVS syncd attributes : No IPVS 64 bit stats : No fwmark socket support : Yes Use VRRP Framework : Yes Use VRRP VMAC : Yes Use VRRP authentication : Yes With ip rules/routes : Yes SNMP vrrp support : No SNMP checker support : No SNMP RFCv2 support : No SNMP RFCv3 support : No DBUS support : No SHA1 support : No Use Debug flags : No smtp-alert debugging : No Use Json output : No Stacktrace support : No Memory alloc check : No libnl version : None Use IPv4 devconf : No Use libiptc : No Use libipset : No init type : systemd Build genhash : Yes Build documentation : No
4. 安装好了之后，在/usr/app/keepalived/etc/keepalived目录下有一个keepalived.conf文件，现在你要做的事情就是
将它copy到/etc/keepalived文件夹下就可以了。
1 [root@localhost keepalived]# ls 2 keepalived.conf samples 3 [root@localhost keepalived]# pwd 4 /usr/app/keepalived/etc/keepalived 5 [root@localhost keepalived]# mkdir -p /etc/keepalived 6 [root@localhost keepalived]# cp ./keepalived.conf /etc/keepalived/keepalived.conf
5. 接下来我们改一下配置文件。
在192.168.23.156机器中的配置文件，修改如下：
【原来】
global_defs { notification_email { acassen@firewall.loc failover@firewall.loc sysadmin@firewall.loc } notification_email_from Alexandre.Cassen@firewall.loc smtp_server 192.168.200.1 smtp_connect_timeout 30 router_id LVS_DEVEL vrrp_skip_check_adv_addr vrrp_strict vrrp_garp_interval 0 vrrp_gna_interval 0 } vrrp_instance VI_1 { state MASTER interface eth0 virtual_router_id 51 priority 100 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.200.16 192.168.200.17 192.168.200.18 } }
【修改】
global_defs { notification_email { acassen@firewall.loc failover@firewall.loc sysadmin@firewall.loc } notification_email_from Alexandre.Cassen@firewall.loc smtp_server 192.168.200.1 smtp_connect_timeout 30 router_id NodeA vrrp_skip_check_adv_addr vrrp_strict vrrp_garp_interval 0 vrrp_gna_interval 0 } vrrp_instance VI_1 { state MASTER interface ens33 virtual_router_id 51 priority 150 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.2.200 } }
其中要注意的就是：
《1》priority 150
节点的优先级，master要比slave高。
《2》interface ens33
ens33大家可以通过ipconfig查看一下自己的网卡。
[root@localhost ~]# ifconfig br-11757db6abf5: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet 172.22.0.1 netmask 255.255.0.0 broadcast 0.0.0.0 ether 02:42:c2:e0:52:10 txqueuelen 0 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 br-875e3c64ec79: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet 172.23.0.1 netmask 255.255.0.0 broadcast 0.0.0.0 ether 02:42:4e:43:5b:a0 txqueuelen 0 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 br-904f2c62861e: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet 172.19.0.1 netmask 255.255.0.0 broadcast 0.0.0.0 ether 02:42:6d:80:36:58 txqueuelen 0 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 br-b0028a425959: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet 172.21.0.1 netmask 255.255.0.0 broadcast 0.0.0.0 ether 02:42:68:51:95:99 txqueuelen 0 (Ethernet) RX packets 18 bytes 1458 (1.4 KiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 41 bytes 3920 (3.8 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 br-c4a09a75fc67: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet 172.18.0.1 netmask 255.255.0.0 broadcast 0.0.0.0 ether 02:42:92:f9:2d:65 txqueuelen 0 (Ethernet) RX packets 4 bytes 340 (340.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 4 bytes 340 (340.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 br-f0fb207788a0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 172.20.0.1 netmask 255.255.0.0 broadcast 0.0.0.0 inet6 fe80::42:86ff:fe1e:c970 prefixlen 64 scopeid 0x20<link> ether 02:42:86:1e:c9:70 txqueuelen 0 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 docker0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet 172.17.0.1 netmask 255.255.0.0 broadcast 0.0.0.0 ether 02:42:8f:8c:a9:a7 txqueuelen 0 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 ens33: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet 192.168.23.157 netmask 255.255.255.0 broadcast 192.168.23.255 inet6 fe80::20c:29ff:fe54:4f5a prefixlen 64 scopeid 0x20<link> ether 00:0c:29:54:4f:5a txqueuelen 1000 (Ethernet) RX packets 10899 bytes 11349012 (10.8 MiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 5575 bytes 599717 (585.6 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 lo: flags=73<UP,LOOPBACK,RUNNING> mtu 65536 inet 127.0.0.1 netmask 255.0.0.0 inet6 ::1 prefixlen 128 scopeid 0x10<host> loop txqueuelen 0 (Local Loopback) RX packets 4 bytes 340 (340.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 4 bytes 340 (340.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 veth4d72ad4: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet6 fe80::d4fb:fcff:feeb:cd7c prefixlen 64 scopeid 0x20<link> ether d6:fb:fc:eb:cd:7c txqueuelen 0 (Ethernet) RX packets 16 bytes 1248 (1.2 KiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 43 bytes 4130 (4.0 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 vethe634b1c: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500 inet6 fe80::e0c6:88ff:fe1c:f4a1 prefixlen 64 scopeid 0x20<link> ether e2:c6:88:1c:f4:a1 txqueuelen 0 (Ethernet) RX packets 18 bytes 1458 (1.4 KiB) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 41 bytes 3920 (3.8 KiB) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 virbr0: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500 inet 192.168.122.1 netmask 255.255.255.0 broadcast 192.168.122.255 ether 00:00:00:00:00:00 txqueuelen 0 (Ethernet) RX packets 0 bytes 0 (0.0 B) RX errors 0 dropped 0 overruns 0 frame 0 TX packets 0 bytes 0 (0.0 B) TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0 [root@localhost ~]#
《3》virtual_ipaddress 192.168.23.200
设置好虚拟IP（VIP）为：192.168.23.200
同样的道理，在192.168.23.157设置如下：
global_defs { notification_email { acassen@firewall.loc failover@firewall.loc sysadmin@firewall.loc } notification_email_from Alexandre.Cassen@firewall.loc smtp_server 192.168.200.1 smtp_connect_timeout 30 router_id NodeB vrrp_skip_check_adv_addr vrrp_strict vrrp_garp_interval 0 vrrp_gna_interval 0 } vrrp_instance VI_1 { state BACKUP interface ens33 virtual_router_id 51 priority 100 advert_int 1 authentication { auth_type PASS auth_pass 1111 } virtual_ipaddress { 192.168.23.200 } }
7. 接下来就可以启动keepalived了。
[root@localhost sbin]# ./keepalived -D [root@localhost sbin]# ps -ef | grep keepalived root 4661 1 0 05:41 ? 00:00:00 ./keepalived -D root 4662 4661 0 05:41 ? 00:00:00 ./keepalived -D root 4663 4661 0 05:41 ? 00:00:00 ./keepalived -D root 4673 4300 0 05:41 pts/0 00:00:00 grep --color=auto keepalived
五：检测
1. 通过ip a 看看当前ens33网卡上是否绑定了192.168.23.200虚拟IP。
2. 然后通过arp -a 查看当前的vip映射到的物理(mac)地址，可以看到当前的vip映射到的是192.168.23.156上面。
C:Usershxc>arp -a 接口: 192.168.23.1 --- 0x6 Internet 地址 物理地址 类型 192.168.23.156 00-0c-29-75-7e-20 动态 192.168.23.157 00-0c-29-54-4f-5a 动态 192.168.23.200 00-0c-29-75-7e-20 动态 192.168.23.255 ff-ff-ff-ff-ff-ff 静态 224.0.0.22 01-00-5e-00-00-16 静态 224.0.0.251 01-00-5e-00-00-fb 静态 224.0.0.252 01-00-5e-00-00-fc 静态 239.11.20.1 01-00-5e-0b-14-01 静态 239.255.255.250 01-00-5e-7f-ff-fa 静态 255.255.255.255 ff-ff-ff-ff-ff-ff 静态
3. 然后我们把156这台机器关闭了，可以看到当前的vip已经漂移到了157这台机器上了。
C:Usershxc>arp -a 接口: 192.168.23.1 --- 0x6 Internet 地址 物理地址 类型 192.168.23.156 00-0c-29-75-7e-20 动态 192.168.23.157 00-0c-29-54-4f-5a 动态 192.168.23.200 00-0c-29-54-4f-5a 动态 192.168.23.255 ff-ff-ff-ff-ff-ff 静态 224.0.0.22 01-00-5e-00-00-16 静态 224.0.0.251 01-00-5e-00-00-fb 静态 224.0.0.252 01-00-5e-00-00-fc 静态 239.11.20.1 01-00-5e-0b-14-01 静态 239.255.255.250 01-00-5e-7f-ff-fa 静态 255.255.255.255 ff-ff-ff-ff-ff-ff 静态
好了，这个就是本篇所说的所有内容，希望对您有帮助。