[Pacemaker] Failed to connection to cluster

[龙龙]

Hii,
   Now,I have two nodes(7 and 3) installed with pacemaker,and the two nodes
are online.But when I try to add a node(4) into the cluster,it can't join
in the current cluster.
The problem description as following:
1.If I start 3 and 7 first,they can works.But when I start 4,it
shows"Failed to connection to cluster".
2.If I start 4 first,it works.Then I start 3 and 7,the two failed to
connection to cluster.And I use crm_mon to see the status,it
shows"Attempting to connnection the Cluster........"
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