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kuldeep7985
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Jul 26, 2024

LDAPS: intermittent login issues

We've integrated Active Directory with F5 ASM. However, we're experiencing intermittent login issues: sometimes we can log in using AD credentials, but other times we get a "remote server authentication failure" error.

  • Hi Kuldeep,

    Intermittent login issues with LDAPS (LDAP over SSL) can be frustrating, especially when integrating Active Directory with F5 ASM.

    Here are some common causes and troubleshooting steps to help resolve these issues:

    Common Causes

    1. Network Issues:
      • Intermittent network connectivity problems can cause authentication failures. Ensure that the network between the F5 device and the Active Directory server is stable and reliable[1].
    2. Certificate Issues:
      • LDAPS requires valid SSL certificates. Ensure that the certificates on both the F5 device and the Active Directory server are correctly configured and not expired[2].
    3. DNS Resolution:
      • Proper DNS resolution is crucial for LDAPS. Ensure that the F5 device can resolve the Active Directory server's hostname correctly[3].
    4. Timeouts and Latency:
      • High latency or timeouts in the network can cause intermittent failures. Check the timeout settings on both the F5 device and the Active Directory server[4].
    5. Load and Performance:
      • High load on the Active Directory server can lead to intermittent authentication failures. Monitor the performance of your AD server to ensure it can handle the authentication requests[1].

    Troubleshooting Steps

    1. Verify Network Connectivity:
      • Use tools like ping and traceroute to check the network connectivity between the F5 device and the Active Directory server.
    2. Check Certificates:
      • Ensure that the SSL certificates are valid and correctly configured. You can use the openssl command to verify the certificates:
      openssl s_client -connect ad_server:636 -showcerts
    3. DNS Configuration:
      • Verify that the F5 device can resolve the Active Directory server's hostname. Use the nslookup command to check DNS resolution:
      nslookup ad_server
    4. Review Logs:
      • Check the logs on both the F5 device and the Active Directory server for any errors or warnings related to authentication. Look for specific error messages that can provide clues to the root cause[5].
    5. Adjust Timeout Settings:
      • Increase the timeout settings on the F5 device to account for network latency. This can help reduce the occurrence of intermittent failures.
    6. Monitor AD Server Performance:
      • Use performance monitoring tools to check the load and performance of your Active Directory server. Ensure it has sufficient resources to handle authentication requests.
    7. Enable Debugging:
      • Enable detailed logging and debugging on the F5 device to capture more information about the authentication process. This can help identify the exact point of failure.

    By following these steps, you should be able to identify and resolve the intermittent login issues with LDAPS. If the problem persists, consider reaching out to F5 support for further assistance[7][6]


    References

    [1] Intermittent issue with LDAP authentication - Windows - Spiceworks ...

    [2] Troubleshoot LDAP over SSL connection problems

    [3] Kerberos authentication troubleshooting guidance - Windows Server ...

    [4] ECS: Intermittent login failures of domain users due to AD or LDAP ...

    [5] Intermittent auth failures with remote LDAP auth for BIG-IP ... - F5, Inc.

    [6] K000138596: Troubleshooting LDAP/LDAPS authentication for ... - F5, Inc.

    [7] LDAPS: intermittent login issues | DevCentral - F5, Inc.

    kindly rate

    HTH

    F5 Design Engineer