Centos5 下构建NAT模式ipvs轮叫服务

在linux中可以做基于NAT的负载均衡，这个也可以再路由器上实现，之前有在cisco路由器上成功实践过，不过这种负载均衡的方式似乎不太健壮，不太适合大型的服务器群集，下面来简单介绍下如何在centos5上配置linux群集的轮叫，所谓轮叫也就是说服务器1响应第一个请求，服务器2响应第二个，如果只有两台服务器，那第三个请求又是服务器1来响应！从而实现比较简单的负载均衡。

在本例中需要有一台双网卡的计算机来担任ipvs服务器，另外两台web服务器的IP同ipvs服务器的中的一个IP在同一个网络，并将网关指向ipvs服务器。下面就来设置下ipvs服务器：
[root@centos5 ~]# ifconfig eth0           (本张网卡模拟外网卡，用来连接公网)
eth0      Link encap:Ethernet HWaddr 00:0C:29:FD:CA:A0
          inet addr:192.168.0.200 Bcast:192.168.0.255 Mask:255.255.255.0
          inet6 addr: fe80::20c:29ff:fefd:caa0/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:832 errors:0 dropped:0 overruns:0 frame:0
          TX packets:543 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:72365 (70.6 KiB) TX bytes:55642 (54.3 KiB)
          Interrupt:185 Base address:0x1400

[root@centos5 ~]# ifconfig eth1          (本张网卡模拟内网，用来连接内部web服务器)
eth1      Link encap:Ethernet HWaddr 00:0C:29:FD:CA:AA
          inet addr:192.168.1.254 Bcast:192.168.1.255 Mask:255.255.255.0
          inet6 addr: fe80::20c:29ff:fefd:caaa/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:68 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:0 (0.0 b) TX bytes:15523 (15.1 KiB)
          Interrupt:169 Base address:0x1480

[root@centos5 ~]# yum search ipvsadm (通过yum服务搜索和安装ipvs软件包)
ipvsadm.i386 : Utility to administer the Linux Virtual Server

[root@centos5 ~]# yum -y install ipvsadm
Setting up Install Process
Parsing package install arguments
Resolving Dependencies
--> Running transaction check
---> Package ipvsadm.i386 0:1.24-8.1 set to be updated
--> Finished Dependency Resolution

Dependencies Resolved

=============================================================================
Package                 Arch       Version          Repository        Size
=============================================================================
Installing:
ipvsadm                 i386       1.24-8.1         base               31 k

Transaction Summary
=============================================================================
Install      1 Package(s)
Update       0 Package(s)
Remove       0 Package(s)

Total download size: 31 k
Downloading Packages:
(1/1): ipvsadm-1.24-8.1.i 100% |=========================| 31 kB    00:03
Running rpm_check_debug
Running Transaction Test
Finished Transaction Test
Transaction Test Succeeded
Running Transaction
Installing: ipvsadm                      ######################### [1/1]

Installed: ipvsadm.i386 0:1.24-8.1
Complete!

[root@centos5 ~]# ipvsadm --version (查看下ipvs的版本信息)
ipvsadm v1.24 2003/06/07 (compiled with popt and IPVS v1.2.0)

[root@centos5 ~]# vi /etc/rc.d/ipvs.sh (通过编辑一个脚本来配置ipvs服务)
#!/bin/sh
echo "1" > /proc/sys/net/ipv4/ip_forward                   启动本机路由功能
ipvsadm -C                                                 清除所有ipvs规则
ipvsadm -A -t 192.168.0.200:80 -s rr                       指定ipvs工作方式为轮叫，其中rr代表为轮叫
ipvsadm -a -t 192.168.0.200:80 -r 192.168.1.55:80 -m -w 1 指定web1的ip和端口
ipvsadm -a -t 192.168.0.200:80 -r 192.168.1.66:80 -m -w 1 指定web2的ip和端口

[root@centos5 ~]# chmod 755 /etc/rc.d/ipvs.sh 执行此脚本
[root@centos5 ~]# /etc/rc.d/ipvs.sh

[root@centos5 ~]# ssh root@192.168.1.66            (配置其他的web服务器，下面以web2为例)
The authenticity of host '192.168.1.66 (192.168.1.66)' can't be established.
RSA key fingerprint is 27:1a:b2:d8:52:30:1e:63:7a:df:9b:de:d6:92:f3:33.
Are you sure you want to continue connecting (yes/no)? yes
Warning: Permanently added '192.168.1.66' (RSA) to the list of known hosts.
root@192.168.1.66's password:
Last login: Sat Apr 25 04:07:57 2009
[root@bogon ~]# cat /etc/sysconfig/network-scripts/ifcfg-eth0 (具体的IP配置信息)
# Advanced Micro Devices [AMD] 79c970 [PCnet32 LANCE]
DEVICE=eth0
BOOTPROTO=static
ONBOOT=yes
HWADDR=00:0c:29:7a:e1:59
IPADDR=192.168.1.66
NETMASK=255.255.255.0
GATEWAY=192.168.1.254
[root@bogon ~]# netstat -ntpl (启动apache服务)
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address               Foreign Address             State       PID/Program name
tcp        0      0 0.0.0.0:111                 0.0.0.0:*                   LISTEN      2510/portmap
tcp        0      0 127.0.0.1:631               0.0.0.0:*                   LISTEN      2803/cupsd
tcp        0      0 127.0.0.1:25                0.0.0.0:*                   LISTEN      2827/sendmail: acce
tcp        0      0 0.0.0.0:601                 0.0.0.0:*                   LISTEN      2539/rpc.statd
tcp        0      0 :::80                       :::*                        LISTEN      3261/httpd
tcp        0      0 :::22                       :::*                        LISTEN      2788/sshd

回到IPVS服务器，确定本机并没有开启80端口

[root@centos5 ~]# netstat -ntpl
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address               Foreign Address             State       PID/Program name
tcp        0      0 0.0.0.0:745                 0.0.0.0:*                   LISTEN      1835/rpc.statd
tcp        0      0 0.0.0.0:111                 0.0.0.0:*                   LISTEN      1810/portmap
tcp        0      0 127.0.0.1:631               0.0.0.0:*                   LISTEN      2124/cupsd
tcp        0      0 127.0.0.1:25                0.0.0.0:*                   LISTEN      2148/sendmail: acce
tcp        0      0 :::22                       :::*                        LISTEN      2101/sshd

下面我们来测试下！

刷新下，可以看到跳转到web2了

本实验以http://www.boobooke.com/v/bbk1614/为指导