AMQP server on c ontroller:5672 is unreachable: [Errno 113] EHOSTUNREACH. Trying again in 2 seconds.，ehostunreach

问题描述：

centos7安装多节点opentack时，nova-compute总是起不来，计算节点的nova-compute日志如下：

2015-06-15 07:20:48.565 16036 INFO nova.virt.driver [-] Loading compute driver 'libvirt.LibvirtDriver'
2015-06-15 07:20:48.571 16036 INFO nova.openstack.common.periodic_task [-] Skipping periodic task _periodic_update_dns because its interval i
s negative
2015-06-15 07:20:48.625 16036 INFO oslo_messaging._drivers.impl_rabbit [req-95a14e35-5e44-49d1-af35-baf3e317be72 - - - - -] Connecting to AMQ
P server on controller:5672
2015-06-15 07:20:48.632 16036 ERROR oslo_messaging._drivers.impl_rabbit [req-95a14e35-5e44-49d1-af35-baf3e317be72 - - - - -] AMQP server on c
ontroller:5672 is unreachable: [Errno 113] EHOSTUNREACH. Trying again in 1 seconds.
2015-06-15 07:20:49.646 16036 ERROR oslo_messaging._drivers.impl_rabbit [req-95a14e35-5e44-49d1-af35-baf3e317be72 - - - - -] AMQP server on c
ontroller:5672 is unreachable: [Errno 113] EHOSTUNREACH. Trying again in 2 seconds.
2015-06-15 07:20:50.660 16036 ERROR oslo_messaging._drivers.impl_rabbit [req-95a14e35-5e44-49d1-af35-baf3e317be72 - - - - -] AMQP server on c
ontroller:5672 is unreachable: [Errno 113] EHOSTUNREACH. Trying again in 2 seconds.
2015-06-15 07:20:51.674 16036 ERROR oslo_messaging._drivers.impl_rabbit [req-95a14e35-5e44-49d1-af35-baf3e317be72 - - - - -] AMQP server on c
ontroller:5672 is unreachable: [Errno 113] EHOSTUNREACH. Trying again in 2 seconds.
2015-06-15 07:20:52.688 16036 ERROR oslo_messaging._drivers.impl_rabbit [req-95a14e35-5e44-49d1-af35-baf3e317be72 - - - - -] AMQP server on c
ontroller:5672 is unreachable: [Errno 113] EHOSTUNREACH. Trying again in 2 seconds.

其他地方无异常，配置文档无异常，防火墙都是关着的

问题解决

启用iptables，在rabbitmq server端加入如下规则，开放rabbitmq端口（5672），允许其他主机访问rabbitmq server：

 # iptables -I INPUT -p tcp --dport 5672 -j ACCEPT
 #添加规则
 # service iptables save
 #保存设置
 # service iptables restart
 # 重启iptables，生效规则

现在再次重启nova-compute服务，发现他可以起来了，问题解决