Steps to Troubleshoot Active Directory Forest Trust Issues:
- Check network connectivity
- Ensure that computers participating in a trust relationship are part of the same network segment.
- Check the quality of the connection.
- Confirm that all domain controllers are reachable over the network.
- Check connctivity between forests
- Verify that required DNS records exist in the DNS Zone of both forests.
- Reconfigure the trust settings between the two forests, if required.
- Confirm that the trust relationship configured on both sides are consistent.
- Verify Kerberos authentication
- Verify that the Kerberos protocol version 5 is enabled on all domain controllers.
- Check security settings on all domain controllers.
- Ensure that SPN is configured properly on the clients.
