PENDING SMS_WSUS_SYNC_Manager: WSUS synchronization failed

[dm91]

Wsus synchronization failed from CAS to one of the Primary Sites.
Error reported in component status:

WSUS Synchronization failed.
Message: UssCommunicationError: WebException: The underlying connection was closed: An unexpected error occurred on a receive. ---> System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote .
Source: Microsoft.SystemsManagementServer.SoftwareUpdatesManagement.WsusSyncAction.WSyncAction.SyncWSUS.

Under WSUS, even when I try to do a manual sync from the primary site, it fails with the same error. Checked the .Net update, TLS1.2 setup on the primary site server.
Just for a brief overview, there are in all 3 primary sites and 1 CAS. other 2 sites sync properly without any issues. There is no firewall that is blocking the sync process between the CAS and primary site.

Please assist, how to troubleshoot this issue in case anybody else faced it before.
SCCM version : 2103

 

[Prajwal Desai]

System.IO.IOException: Unable to read data from the transport connection: An existing connection was forcibly closed by the remote - I know you are confident that firewall isn't the cause here but can you check with your network team and confirm that any other security device isn't blocking this.

 

[dm91]

Okay, i will reach out to them and update the thread. Thank you for the suggestion.

 

[Prajwal Desai]

Let us know if there is any update on this issue.

 

[dm91]

It was indeed a firewall issue. Even though we were able to connect on the port between the two sites for a brief time, firewall was terminating the connection prematurely. Thanks for assisting. Appreciate it.