The Knowledge Consistency Checker (KCC) is a component of Active Directory Domain Services (AD DS) that is responsible for generating the replication topology between domain controllers. Generating an efficient and fault-tolerant replication topology is an integral part of achieving data consistency between domain controllers.

Event Details

Resolve

Allow the KCC to compute the replication path

To make it possible for the Knowledge Consistency Checker (KCC) to compute the replication path:

• Ensure that the domain controllers that host the identified directory partition are accessible.
• Ensure that adequate site connectivity exists.

Ensure that the domain controllers that host the identified directory partition are accessible

Perform the following procedure on each domain controller that hosts the partition for which the KCC is reporting that a replication path cannot be computed. Start with the domain controller that is reporting this issue.

To perform this procedure, you must have membership in Domain Admins, or you must have been delegated the appropriate authority.

To ensure that the domain controllers that host the identified directory partition are accessible:

1. Open a command prompt as an administrator. To open a command prompt as an administrator, click Start. In Start Search, type Command Prompt. At the top of the Start menu, right-click Command Prompt, and then click Run as administrator. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Continue.
2. Run the command dcdiag /test:connectivity. If you are running the command remotely, you can add the command line switch /s:computername to the command to target a specific computer (substitute the name of the computer you want to query for computername). This command tests whether the domain controllers are available and properly registered with the domain name system (DNS) servers. Resolve any issues that you find when you run this test. Look in the System Log in Event Viewer on the affected domain controller if you have reason to believe that there is a network connectivity issue with the domain controller.

Note: This situation also can occur if there are domain controllers in the directory that no longer exist. If a domain controller was removed and the metadata for the server was not properly cleaned up, see Clean up server metadata (http://go.microsoft.com/fwlink/?LinkID=104231).

Ensure that adequate site connectivity exists

One of the issues that may cause this error is that not all the sites have adequate connectivity. You can use the Active Directory Sites and Services snap-in to ensure that sites, site links, and bridges are configured correctly. This section walks you through a quick check of your sites and site link bridges in Active Directory Sites and Services. For more information, see the Step-by-Step Guide to Active Directory Sites and Services (http://go.microsoft.com/fwlink/?LinkId=104532).

To perform these procedures, you must have membership in Enterprise Admins, or you must have been delegated the appropriate authority.

To ensure that adequate site connectivity exists:

1. If you are not currently logged on with an account that has membership in the Enterprise Admins group, you can use the runas command to open a command prompt with elevated credentials. To do this, click Start in Start Search, type runas /user:domain\account cmd, and then press ENTER. Substitute the actual domain name and user account name of an account that is a member of the Enterprise Admins group for domain and user. Type the password for the account when you are prompted. A command prompt opens under the security context of the account that you provided.
2. To open Active Directory Sites and Services, at the command prompt type dssite.msc, and then press ENTER.
3. In the console tree, ensure that Sites is expanded.
4. For each site that has servers hosting the partition that is referred to in the event message text, expand the site object and the server objects that it contains.
5. Expand Inter-Site Transports. Two subordinate objects are revealed: IP and SMTP.
6. Click the intersite transport that your network uses to replicate. If you are not sure which intersite transport your network uses, click both intersite transports until you see site link objects. If only one intersite transport, IP or SMTP, has site link objects, that is the transport that is in use. Select that object. If both intersite transports have site link objects, both of them are probably in use. In that case, check both intersite transport objects as you complete the following steps.
7. In the details pane, right-click each site link, and then click Properties.
8. Note the sites that are listed under Sites in this site link. Ensure that all sites are appropriately connected. Repeat this and the previous two steps until you have confirmed that all sites are connected to one another through site links. If necessary, create additional site links to ensure that all sites are connected appropriately.
9. Right-click the appropriate intersite transport object (IP or SMTP), and then click Properties. Note whether the Bridge all site links check box is selected. If the check box is selected, you do not have to configure site link bridges for the transport. If the check box is not selected, configure appropriate site link bridges or select the Bridge all site links check box.
10. Click OK. If necessary, create additional site link bridges to ensure that all site links are connected appropriately.

For additional information about resolving Event ID 1865, see article 944351 in the Microsoft Knowledge Base (http://go.microsoft.com/fwlink/?LinkId=109266). For additional information about resolving Event ID 1311, see article 307593 in the Microsoft Knowledge Base (http://go.microsoft.com/fwlink/?LinkId=109273).

Verify

Perform the following procedure on the domain controller on which you want to verify that the Knowledge Consistency Checker (KCC) is functioning.

To perform this procedure, you must have membership in Domain Admins, or you must have been delegated the appropriate authority.

To verify that the KCC is computing replication paths:

1. Open a command prompt as an administrator. To open a command prompt as an administrator, click Start. In Start Search, type Command Prompt. At the top of the Start menu, right-click Command Prompt, and then click Run as administrator. If the User Account Control dialog box appears, confirm that the action it displays is what you want, and then click Continue.
2. Run the command repadmin /kcc. This command starts KCC translation of domain controllers, to which the local domain controller replicates.

Check Event Viewer to see if there are any failure messages that are related to the KCC. If there are no error events that are related to the KCC, it is functioning properly. If there are error events, use the additional information in them to resolve the issue.

Related Management Information

KCC Replication Path Computation (TechNet Library)

Active Directory (TechNet Library)