How to fix "421 Service Not Available, Closing Control Connection" on Network Management Card When Trying To Enter any SFTP Client Connections
Issue:
How to fix "421 Service Not Available, Closing Control Connection" on Network Management Card When Trying To Enter any SFTP Client Connections
Product Line:
Network Management Card 2 (NMC2) - AP9630/AP9631 version 6.x.x above
- Devices with an embedded Network Management Card 2 include (but are not limited to): Early model 2G Metered/Switched Rack PDUs (AP78, AP79, AP84, AP86, AP88, AP89), Rack Automatic Transfer Switches (AP44XX), Certain Audio/Video Network Management Enabled products, Early model Smart-UPS Online (SRT).
Network Management Card 3 (NMC3) - AP9640/AP9641 version 1.x.x.x above
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Devices with an embedded Network Management Card 3 include (but are not limited to): Metered/Switched Rack PDUs (AP78, AP79, AP84, AP86, AP88, AP89, APDU9), Rack Automatic Transfer Switches (AP44A), Smart-UPS Online (SRT), SRTL2K-3K, Smart-UPS Modular Ultra 5kva to 20kva.
Network Management Card 3 (NMC3) - AP9544, AP9547
Environment:
All serial numbers
Cause:
The "421 Service Not Available, Closing Control Connection" error occurs when the Network Management Card has an active FTP connection and cannot accept any new connections.
Resolution:
The network card only accepts one (1) active FTP session. You can clear active or stuck user sessions directly from the NMC Web GUI or NMC Command Line Interface (CLI). The following steps highlight how to delete active or stuck user session in FTP to accept new connections.
Disclaimer: Before terminating an active connection, first confirm its purpose. The connection may be supporting an important task, such as a firmware upgrade, diagnostics, or system maintenance. Disconnecting it without verification may disrupt operations or cause unexpected issues. When unsure, seek clarification before proceeding.
For NMC Web GUI
1. Open an NMC Web GUI session.
2. Log in using the NMC username and password.
3. Navigate to Control -->Security -->Session Management to terminate/view sessions.
4. Click on a username --> terminate session. Note: Only a Super User or Administrator has this capability
For NMC Web CLI
1. Open an NMC Web GUI session.
2. Log in using the NMC username and password.
3. Navigate to Control -->Network-->Web CLI to access NMC Web CLI.
4. Type "session" to view active connections.
5. Type "session -d [ID]" to delete a specific session (e.g., session -d 6).
Note: Repeat steps until all unnecessary web sessions have been removed.
6. Once there are no active sessions, exit the Web GUI, SSH, Telnet, or Direct Connection.
7. Try to access the FTP session and confirm that access is good.
For NMC Command Line Interface (CLI)
Open an SSH or Telnet client (for example, PuTTY). Log in using your username and password, then follow steps 4 through 7 in the "For NMC Web GUI CLI".
Note: If the NMC Web UI, SSH, or Telnet is inaccessible, you may use a direct connection by following the instructions in FA156366
In most cases, this issue can be resolved by reseating the network card or restarting it through SSH, Telnet, or the card's pinhole reset button.
Should there be any other questions and/or concerns, feel free to reach out to us at 1-800-800-4272 or via chat with our technical support group at APC by Schneider Electric Customer Technical Support
Released for: Schneider Electric United Arab Emirates
