Snippet Name: CNAME_SMB_Share_Access

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Created Date: 2025-06-16 13:12:42
Last Modified Date: 2025-05-31 10:31:49

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Title: CNAME SMB Share Access
Author: user
i have a server with a fileshare :\\vmprodwdbrs01.cigfinancial.com\Reports. i've created a cname AZU-V1-RS01 which points to the aname record for vmprodwdbrs01. i can access the share but not the smae share with the cname \\AZU-V1-RS01\Reports

Author: ChatGPT
It sounds like you're encountering an issue where the share path `\\vmprodwdbrs01.cigfinancial.com\Reports` works, but the same share cannot be accessed using the CNAME `\\AZU-V1-RS01\Reports`.

This is a common issue with Windows and how it handles CNAMEs. By default, Windows does not allow access to SMB shares using a CNAME due to a security feature called **strict name checking**. Here???s how you can resolve it:

### Steps to allow access via CNAME:
1. **Disable Strict Name Checking** on the server where the file share is hosted (`vmprodwdbrs01`):
   - Open the **Registry Editor** (`regedit`).
   - Navigate to the following key:
     ```
     HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\LanmanServer\Parameters
     ```
   - Add a new **DWORD (32-bit) Value**:
     - Name: `DisableStrictNameChecking`
     - Value: `1`
   - Restart the server for the changes to take effect.

2. **Optional: Add a BackConnectionHostNames entry** (if needed):
   - If you continue to experience issues, you can add the CNAME to the `BackConnectionHostNames` list.
   - In the **Registry Editor**, navigate to:
     ```
     HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0
     ```
   - Add a new **Multi-String Value**:
     - Name: `BackConnectionHostNames`
     - Value: Add `AZU-V1-RS01` (your CNAME) in the list.
   - Restart the server if needed.

These steps should allow access to the SMB share using both the original name and the CNAME. Let me know if you run into any issues or need further clarification!

Author: user
i created a second cname AZU-V2-RS01 which also points to the vmprodwdbrs01; do i need multiple entries?

Author: ChatGPT
Yes, if you have multiple CNAMEs pointing to the same server (like `AZU-V1-RS01` and `AZU-V2-RS01`), you will need to add all of those CNAMEs to the `BackConnectionHostNames` entry on the server. Here???s how you can update the registry to support multiple CNAMEs:

### Update `BackConnectionHostNames` with Multiple CNAMEs:
1. Open **Registry Editor** (`regedit`).
2. Navigate to:
   ```
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Lsa\MSV1_0
   ```
3. Locate the **Multi-String Value** named `BackConnectionHostNames`. If it does not exist, create it:
   - Right-click, choose **New** > **Multi-String Value**.
   - Name it `BackConnectionHostNames`.
4. Edit the `BackConnectionHostNames` entry:
   - Double-click the `BackConnectionHostNames` entry.
   - In the **Value data** field, add each CNAME on a new line. For example:
     ```
     AZU-V1-RS01
     AZU-V2-RS01
     ```
5. Click **OK** and restart the server.

This will ensure that both `AZU-V1-RS01` and `AZU-V2-RS01` CNAMEs are recognized by the server, allowing SMB share access via either alias.

Author: user
i get a similar error when trying to use Remote Desktop so far: [Window Title]
Remote Desktop Connection

[Content]
The connection cannot be completed because the remote computer that was reached is not the one you specified. This could be caused by an outdated entry in the DNS cache. Try using the IP address of the computer instead of the name.

[OK]

Author: ChatGPT
The error you're encountering with Remote Desktop is related to **Remote Desktop Protocol (RDP)** and its security mechanism that checks for mismatches between the hostname you used and the certificate presented by the remote machine. This issue often arises when using CNAMEs or DNS aliases, as RDP expects the certificate's subject name to match the actual computer name.

Here's how you can resolve this issue:

### Option 1: Use the Target Server's Actual Name
If possible, use the server's real name (`vmprodwdbrs01.cigfinancial.com`) when connecting via Remote Desktop, as the certificate will match this name.

### Option 2: Disable NLA Name Check for CNAME (Allow DNS Aliases for RDP)
You can modify the **Remote Desktop Security** settings to allow connections using DNS aliases (CNAMEs). Follow these steps:

1. **Edit Registry on the Remote Machine (`vmprodwdbrs01`)**:
   - Open **Registry Editor** (`regedit`).
   - Navigate to:
     ```
     HKEY_LOCAL_MACHINE\System\CurrentControlSet\Control\Terminal Server\WinStations\RDP-Tcp
     ```
   - Create a new **DWORD (32-bit) Value**:
     - Name: `DisableStrictNameChecking`
     - Value: `1`

2. **Flush DNS Cache**:
   After making changes, you may want to flush the DNS cache on the client machine (the one you're using to initiate the RDP session):
   - Open **Command Prompt** as Administrator and run the following command:
     ```
     ipconfig /flushdns
     ```

3. **Restart the Remote Machine**:
   Restart the target server (`vmprodwdbrs01`) for the changes to take effect.

### Option 3: Use Remote Desktop with the IP Address
As suggested in the error message, you can also connect using the **IP address** of the server instead of the DNS alias, which should avoid the certificate mismatch.

Let me know if you need any further assistance!

Author: user
i beleive i am getting errors related to NTLM, and old service principal names. what is the command to create a service principal name for the cname

Author: ChatGPT
To resolve issues related to NTLM and old Service Principal Names (SPNs), you can manually create an SPN for the CNAME that points to your server. SPNs are required by services like Kerberos to associate a service instance with a domain account, and they must match the name clients use to connect (in your case, the CNAME).

Here???s how to create an SPN for your CNAME:

### Step-by-Step to Create an SPN for a CNAME:

1. **Open a Command Prompt** as an Administrator on the Domain Controller or a machine with the necessary Active Directory tools.

2. **Run the `setspn` Command**:
   The format for the `setspn` command is:
   ```
   setspn -A <SPN> <Domain\Account>
   ```

   - Replace `<SPN>` with the service name and the CNAME.
   - Replace `<Domain\Account>` with the name of the server's domain account (usually the computer account).

#### Example for an SMB Share:
For SMB file shares, the SPN would look like this:

   If your CNAME is `AZU-V1-RS01`, and the server's account is `vmprodwdbrs01$` (the default computer account in Active Directory):
   ```
   setspn -A HOST/AZU-V1-RS01 vmprodwdbrs01$
   ```

   Similarly, for the second CNAME:
   ```
   setspn -A HOST/AZU-V2-RS01 vmprodwdbrs01$
   ```

   If you're using RDP, add the SPN for the Remote Desktop service:
   ```
   setspn -A TERMSRV/AZU-V1-RS01 vmprodwdbrs01$
   setspn -A TERMSRV/AZU-V2-RS01 vmprodwdbrs01$
   ```

3. **Verify the SPNs**:
   After registering the SPNs, you can verify them by running the following command:
   ```
   setspn -L vmprodwdbrs01$
   ```
   This will list all the SPNs registered for the server account, ensuring the new entries are correct.

4. **Restart Services or the Server**:
   After registering the SPNs, restart the services related to file sharing (SMB) or Remote Desktop for the changes to take effect.

### Important Notes:
- SPNs are case-sensitive, so ensure that the CNAME and service names match exactly.
- Be careful when modifying SPNs, as duplicates or incorrect entries can cause authentication failures.
  
Let me know if you run into any other issues!

Author: user
i get an error Duplicate SPN Found, how do i correct

Author: ChatGPT
The "Duplicate SPN Found" error occurs when an SPN is already registered to another account or incorrectly registered multiple times. This can cause authentication issues, especially with Kerberos. Here's how to resolve the issue:

### Steps to Correct Duplicate SPNs:

1. **Identify the Duplicate SPN**:
   Use the following command to search for the duplicate SPN and identify which accounts have it registered:
   ```
   setspn -X
   ```
   This will check for duplicate SPNs across all accounts in Active Directory and list them.

   Alternatively, you can search for the specific SPN manually:
   ```
   setspn -Q <SPN>
   ```
   For example, to search for `HOST/AZU-V1-RS01`, use:
   ```
   setspn -Q HOST/AZU-V1-RS01
   ```

   This will tell you which accounts have the conflicting SPN registered.

2. **Remove the Duplicate SPN**:
   Once you've identified the accounts with the duplicate SPN, you can remove the incorrect or duplicate entry using the `setspn` command:
   ```
   setspn -D <SPN> <Domain\Account>
   ```
   For example, to remove the SPN `HOST/AZU-V1-RS01` from an account, the command would look like this:
   ```
   setspn -D HOST/AZU-V1-RS01 other-account$
   ```

   Replace `other-account$` with the actual account name that incorrectly holds the SPN.

3. **Re-Add the Correct SPN** (Optional):
   After removing the duplicate, if necessary, re-register the SPN to the correct account (e.g., `vmprodwdbrs01$`):
   ```
   setspn -A HOST/AZU-V1-RS01 vmprodwdbrs01$
   ```

4. **Verify the Changes**:
   After making the corrections, verify that the SPNs are correctly set by listing the SPNs for the server:
   ```
   setspn -L vmprodwdbrs01$
   ```
   This will ensure that the SPN is registered properly to the correct account without any duplicates.

### Important Notes:
- SPN conflicts are usually caused by multiple computer or service accounts registering the same SPN. Make sure you only register the SPN to the correct account (e.g., the account running the service or computer hosting the share).
- Be cautious when removing SPNs from an account, especially if the account is tied to important services.

Let me know how it goes or if you need further clarification!