按照官方文档的描述在server.xml的Engine元素中增加cluster子元素，配置如下：
但是，在我的linux虚拟机上面启动tomcat时总是如下错误：
信息: Starting Servlet Engine: Apache Tomcat/7.0.62
七月 07, 2015 10:15:38 上午 org.apache.catalina.ha.tcp.SimpleTcpCluster startInternal
信息: Cluster is about to start
七月 07, 2015 10:15:38 上午 org.apache.catalina.tribes.transport.ReceiverBase bind
信息: Receiver Server Socket bound to:/127.0.0.1:4000
七月 07, 2015 10:15:38 上午 org.apache.catalina.tribes.membership.McastServiceImpl setupSocket
信息: Setting cluster mcast soTimeout to 500
七月 07, 2015 10:15:38 上午 org.apache.catalina.tribes.membership.McastServiceImpl start
严重: Unable to join multicast group, make sure your system has multicasting enabled.
七月 07, 2015 10:15:38 上午 org.apache.catalina.ha.tcp.SimpleTcpCluster startInternal
严重: Unable to start cluster.
org.apache.catalina.tribes.ChannelException: java.net.SocketException: 没有那个设备; No faulty members identified.
at org.apache.catalina.tribes.group.ChannelCoordinator.internalStart
(ChannelCoordinator.java:177)
at org.apache.catalina.tribes.group.ChannelCoordinator.start
(ChannelCoordinator.java:98)
at org.apache.catalina.tribes.group.ChannelInterceptorBase.start
(ChannelInterceptorBase.java:160)
at org.apache.catalina.tribes.group.interceptors.MessageDispatchInterceptor.start
(MessageDispatchInterceptor.java:157)
at org.apache.catalina.tribes.group.ChannelInterceptorBase.start
(ChannelInterceptorBase.java:160)
at org.apache.catalina.tribes.group.ChannelInterceptorBase.start
(ChannelInterceptorBase.java:160)
at org.apache.catalina.tribes.group.GroupChannel.start
(GroupChannel.java:419)
at org.apache.catalina.ha.tcp.SimpleTcpCluster.startInternal
(SimpleTcpCluster.java:690)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1106)
at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:300)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.StandardService.startInternal(StandardService.java:443)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:739)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
at org.apache.catalina.startup.Catalina.start(Catalina.java:689)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:321)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:455)
Caused by: java.net.SocketException: 没有那个设备
at java.net.PlainDatagramSocketImpl.join(Native Method)
at java.net.AbstractPlainDatagramSocketImpl.join(AbstractPlainDatagramSocketImpl.java:179)
at java.net.MulticastSocket.joinGroup(MulticastSocket.java:319)
at org.apache.catalina.tribes.membership.McastServiceImpl.start(McastServiceImpl.java:253)
at org.apache.catalina.tribes.membership.McastService.start(McastService.java:444)
at org.apache.catalina.tribes.group.ChannelCoordinator.internalStart(ChannelCoordinator.java:162)
... 22 more
七月 07, 2015 10:15:38 上午 org.apache.catalina.startup.Catalina start
严重: The required Server component failed to start so Tomcat is unable to start.
org.apache.catalina.LifecycleException: Failed to start component [StandardServer[8005]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
at org.apache.catalina.startup.Catalina.start(Catalina.java:689)
at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:57)
at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
at java.lang.reflect.Method.invoke(Method.java:606)
at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:321)
at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:455)
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardService[Catalina]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
at org.apache.catalina.core.StandardServer.startInternal(StandardServer.java:739)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 7 more
Caused by: org.apache.catalina.LifecycleException: Failed to start component [StandardEngine[Catalina]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
at org.apache.catalina.core.StandardService.startInternal(StandardService.java:443)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 9 more
Caused by: org.apache.catalina.LifecycleException: Failed to start component [org.apache.catalina.ha.tcp.SimpleTcpCluster[Catalina]]
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:154)
at org.apache.catalina.core.ContainerBase.startInternal(ContainerBase.java:1106)
at org.apache.catalina.core.StandardEngine.startInternal(StandardEngine.java:300)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 11 more
Caused by: org.apache.catalina.LifecycleException: org.apache.catalina.tribes.ChannelException: java.net.SocketException: 没有那个设备; No faulty members identified.
at org.apache.catalina.ha.tcp.SimpleTcpCluster.startInternal(SimpleTcpCluster.java:695)
at org.apache.catalina.util.LifecycleBase.start(LifecycleBase.java:150)
... 14 more
Caused by: org.apache.catalina.tribes.ChannelException: java.net.SocketException: 没有那个设备; No faulty members identified.
at org.apache.catalina.tribes.group.ChannelCoordinator.internalStart(ChannelCoordinator.java:177)
at org.apache.catalina.tribes.group.ChannelCoordinator.start(ChannelCoordinator.java:98)
at org.apache.catalina.tribes.group.ChannelInterceptorBase.start(ChannelInterceptorBase.java:160)
at org.apache.catalina.tribes.group.interceptors.MessageDispatchInterceptor.start(MessageDispatchInterceptor.java:157)
at org.apache.catalina.tribes.group.ChannelInterceptorBase.start(ChannelInterceptorBase.java:160)
at org.apache.catalina.tribes.group.ChannelInterceptorBase.start(ChannelInterceptorBase.java:160)
at org.apache.catalina.tribes.group.GroupChannel.start(GroupChannel.java:419)
at org.apache.catalina.ha.tcp.SimpleTcpCluster.startInternal(SimpleTcpCluster.java:690)
... 15 more
Caused by: java.net.SocketException: 没有那个设备
at java.net.PlainDatagramSocketImpl.join(Native Method)
at java.net.AbstractPlainDatagramSocketImpl.join(AbstractPlainDatagramSocketImpl.java:179)
at java.net.MulticastSocket.joinGroup(MulticastSocket.java:319)
at org.apache.catalina.tribes.membership.McastServiceImpl.start(McastServiceImpl.java:253)
at org.apache.catalina.tribes.membership.McastService.start(McastService.java:444)
at org.apache.catalina.tribes.group.ChannelCoordinator.internalStart(ChannelCoordinator.java:162)
... 22 more
七月 07, 2015 10:15:38 上午 org.apache.coyote.AbstractProtocol pause
信息: Pausing ProtocolHandler ["http-bio-8080"]
七月 07, 2015 10:15:38 上午 org.apache.coyote.AbstractProtocol pause
信息: Pausing ProtocolHandler ["ajp-bio-8009"]
七月 07, 2015 10:15:38 上午 org.apache.catalina.core.StandardService stopInternal
信息: Stopping service Catalina
七月 07, 2015 10:15:38 上午 org.apache.coyote.AbstractProtocol destroy
信息: Destroying ProtocolHandler ["http-bio-8080"]
七月 07, 2015 10:15:38 上午 org.apache.coyote.AbstractProtocol destroy
信息: Destroying ProtocolHandler ["ajp-bio-8009"]
我猜测应该是组播的问题，本质上讲是我虚拟机的网络那块有问题，导致无法加入组播组。
后来，在网上搜集了一些资料，都没有什么好的方案
有人说将Receiver的address改成自己的ip地址，不要用auto
也有人说是hostname和/etc/hosts中配置不一致
更有人说是因为没有插网线
……
我都试过，无奈还是报这个错，即使我把SELinux和防火墙都关了亦是如此。
后来，我将tomcat放到我的win7上面可以启动成功（即使拔掉网线）
我想，放到win7下可以，放到linux上呢？，我将虚拟机中那个无法启动的tomcat又放到公司的
linux服务器上，竟然也能启动成功。我很困惑……
后来，我将虚拟机上的网卡eth0的广播地址改成228.0.0.4
ipconfig eth0 broadcast 228.0.0.4
再次启动tomcat，天呐，经常启动成功了，不知道为什么……
最后，我做了一个大胆的尝试
我将虚拟机的网络连接方式由“仅主机模式”改成“桥接模式”，让虚拟机能够联网
又一次在虚拟机中启动tomcat，结果启动成功了，很意外
在网络连接方式为“仅主机模式”的虚拟机环境中启动tomcat，报错
将虚拟机的广播地址改成228.0.0.4，启动tomcat，成功
将虚拟机中的那个tomcat放到win7环境和真实的linux服务器上启动成功
不改变虚拟机的广播地址，将网络连接方式改为“桥接模式”，启动tomcat，也成功
就这么稀里糊涂的，tomcat的就启动成功了，我也不知道这是为什么，看来虚拟机环境还是有问题啊！
这里也懒得往下深究了，总之，做实验就用桥接模式吧！
日后遇到高人再请教吧………………
