A new connection has been created to address site connectivity issues. One or more sites are unreachable in the topology. ...

A new connection has been created to address site connectivity issues.
  
  One or more sites are unreachable in the topology. The sites may be unreachable due to site link  configuration errors, or by bridgeheads in those sites having errors. The KCC is attempting to  reform the topology by excluding those sites.  This new connection bypasses sites that are down.
  
  A new failover connection is being created in an attempt to reestablish connectivity in the  topology. These temporary connections will be removed once the sites are functioning again.  This is a normal response to correct the topology.
  
  A replication connection was created from the following source domain controller to the local domain controller.  
  
Source domain controller:
%1  
Local domain controller:
%2  
  
Additional data:  
Reason Code:
0x%3  
Creation Point Internal ID:
%4  
  
User action:  
Check for previous site or bridgehead errors. Verify that site links are configured correctly.  Verify that bridgeheads are responding. Check for and correct replication errors on bridgeheads  using monitoring tools such as repadmin.exe or dcdiag.exe. If this failover is not desired, please  adjust the registry keys controlling failover policy.  Frequent failover may be a sign of intermittent  bridgehead connectivity or bridgehead instability.