When a backup is performed, Amanda will use a source port on the Amanda server to connect with the client on the client's port, 10080. The backup of each of the different clients that Amanda connects with is performed through the same source port on the Amanda server.
Additional source ports are opened on the Amanda server when Amanda requires additional connections to the same client. It commonly occurs if more than one Backup Set is being run at the same time and contains the same client(s) or if Parallel Backups (Client) on Backup How is set to a number greater than 1 for any Backup Set.
The source port range that Amanda Enterprise uses by default is from port 800 to 840, and Amanda will not use a port number that is already assigned by the IANA. Suppose this does not allow enough available source ports for the Amanda server, given the backups being performed. In that case, the source port range can be increased.
Increase the source port range used by Amanda Enterprise in the Ports for Parallel Backups field on the Backup How page.
