组建tomcat集群时明明配置都没问题，tomcat就是起不来，查看日志得到
SEVERE: Unable to join multicast group, make sure your system has multicasting enabled.
的信息，最后才知道，没有设置网关。。。。。。。真坑！！！记录下来第一个坑！！！
本文出自 “机制小风风” 博客，请务必保留此出处http://xiaofengfeng.blog.51cto.com/8193303/1896514
SEVERE: Unable to join multicast group, make sure your system has multicasting enabled.
原文：http://xiaofengfeng.blog.51cto.com/8193303/1896514