AMQP Server on C ontroller:5672 is unreachable: [Errno 113] Ehostunreach. Trying again in 2 seconds.

Problem Description:

CENTOS7 When installing multi-node Opentack, Nova-compute always fails, and the Nova-compute log of the compute nodes is as follows:

 
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.

No exception anywhere else, no exception in configuration document, firewall is closed

Problem solving

Enable Iptables, add the following rule on the RABBITMQ server side, open the RABBITMQ port (5672), and allow other hosts to access RABBITMQ server:

# iptables -I INPUT -p tcp --dport 5672 -j ACCEPT
  #Add rules
  # service iptables save
  #Save Settings
  # service iptables restart 

Now restart the Nova-compute service again and find that he can get up and solve the problem

AMQP Server on C ontroller:5672 is unreachable: [Errno 113] Ehostunreach. Trying again in 2 seconds.