Sudden connectivity loss to a resource

Use this information to troubleshoot issues when a device or infrastructure resource goes offline.

Check the event log for any network events for the resource, and resolve those first. For more information about the event log, see Monitoring events.
Attempt to log in directly to the resource, and ensure that the credentials have not changed.
Ensure that the IP address of the resource is valid for the network. Ping the resource to test if it is visible on the network.
Ensure that the network hardware is functioning correctly for the connection path to the resource.
Ensure that the correct switch and firewall ports are enabled for the resource. For information about required ports, see Port availability.
If the encapsulation mode is encapsulationLite on managed devices, the following situations might cause communication and authentication issues between the resource manager and managed devices, rendering the managed devices unreachable. Because the devices are configured to ignore TCP requests from other sources, it is not possible to access those devices through a network interface. In most cases, these devices do not respond to ping, SSH or TELNET requests.
- Network changes on the hypervisor in which the resource manager runs
- Virtual Local Area Networks (VLANs) or VLAN tags changes
- Permanent changes to device IP addresses while encapsulation is enabled
- Force-unmanagement of a device while encapsulation is enabled
- Loss of the resource manager virtual machine
- Loss of TCP communication between the virtual machine and the managed devices
- Other network issues that prevent the resource manager from communicating directly with managed devices while encapsulation mode is enabled
If a permanent problem occurs, complete one of the following actions to recover access to the previously managed devices. For more information, see Encapsulation management, Recovering management with a CMM after a management server failure, and Recovering management with a CMM after a management server failure in the XClarity Administrator online documentation.
- To recover the access to a managed IMM where encapsulation mode is active, the default settings must be loaded from local console through UEFI graphical user interface.
- Use the USB-to-Ethernet bridge to gain in-band access to the management controller, and run the following command:
```
encaps lite -off
```
- To recover access to a managed CMM where encapsulation mode is active, the default settings must be loaded using the rear reset button or by running the following command if the console can still be reached:
```
accesscontrol -off -T mm[p]
```

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