Overcoming SQL Server Error 1418 in Always On Availability Groups with SQLOPS 

Nigel Menezes
Overcoming SQL Server Error 1418 in Always On Availability Groups with SQLOPS

SQL Server Always On Availability Groups and Database Mirroring are critical components of SQL Server’s high availability and disaster recovery solutions. However, setting up these features can sometimes hit a snag, particularly with Error 1418, which prevents successful communication between replicas. This guide by SQLOPS delves into the troubleshooting steps to resolve Error 1418, ensuring your SQL Server deployment achieves the desired level of availability and resilience. 

Understanding Error 1418 in SQL Server 

Error 1418 is typically triggered during the initial setup or addition of replicas to an Always On Availability Group, indicating a failure in the session establishment necessary for replication and mirroring. 

Common Causes: 

  • Network connectivity issues between the primary and secondary servers. 
  • Incorrect configuration of database mirroring endpoints. 
  • Authentication failures, often related to the SQL Server service account. 

Steps to Resolve Error 1418 

Ensure Network Connectivity 

Objective: Confirm that the primary and secondary servers can communicate over the network without hindrances. 

Network Tests: 

Utilize tools such as ping and telnet to verify basic connectivity and port accessibility. Ensuring that firewalls and network security groups (if applicable) allow traffic on the relevant ports (default is 5022 for SQL Server endpoints) is crucial. 

Configure Endpoints Correctly 

Properly setting up and securing database mirroring endpoints is essential for communication between replicas. 

Create/Alter Endpoints: 

Ensure that the endpoints on all replicas are configured to listen on the correct port and are accessible. Use the following T-SQL to create or modify an endpoint, substituting your specific settings: 

    AS TCP (LISTENER_PORT = 5022) 
        ROLE = ALL); 


Verify Authentication 

SQL Server uses the service account for endpoint authentication by default. Ensuring this account has the necessary permissions on both the primary and secondary servers is vital. 

SQL Service Account Permissions: 

  • Confirm that the SQL Server service account is correctly configured and has sufficient permissions on both the primary and secondary servers. 
  • In cross-domain setups, consider using certificate-based authentication for endpoints to avoid common authentication issues. 

Attempt Mirroring or AG Setup Again 

With connectivity confirmed, endpoints correctly configured, and authentication issues addressed, retry setting up the database mirroring or adding the replica to the Always On Availability Group. 

Use SQL Server Management Studio (SSMS): 

  • Navigate through the Always On High Availability wizard in SSMS to add the secondary replica, carefully following each step to ensure all configurations are correct. 


Error 1418 can be a daunting obstacle when configuring SQL Server’s high availability features, but it is often surmountable with careful attention to network settings, endpoint configurations, and authentication details. By following the steps outlined by SQLOPS, database administrators can effectively overcome this challenge, securing their SQL Server environments against unexpected downtimes and ensuring continuous availability. 

If you’re facing persistent issues with SQL Server Always On Availability Groups or need expert advice on optimizing your SQL Server environment for high availability, SQLOPS is here to help. Our team of seasoned professionals offers a wide range of services designed to bolster your database infrastructure. Discover more about how we can support your SQL Server deployments at SQLOPS

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