The BIND 9.x server implementation must have fetches-per-server enabled.

The fetches-per-server option in BIND 9.x configures a limit on the number of outstanding requests (fetches) allowed for a single DNS server. This rate-limiting mechanism helps protect the BIND 9.x server from being overwhelmed by excessive requests to a specific server, particularly when that server is slow or unresponsive.

Verify fetches-per-server is enabled with an organization-defined number.

Inspect the named.conf file for the following:

options { fetches-per-server <integer> drop ;

If fetches-per-server is not enabled and set to drop, this is a finding.

Modify the BIND configuration file (/etc/named.conf ).

Add the fetches-per-server option to the "options" section of the configuration file.

fetches-per-server <integer> drop;

After making changes, reload or restart BIND to apply the new settings.