Document link:
https://docs.redhat.com/en/documentation/red_hat_enterprise_linux/9/html/configuring_and_using_network_file_services/deploying-an-nfs-server_configuring-and-using-network-file-services#key-features-of-minor-nfsv4-versions_deploying-an-nfs-server

Section number and name:
2.7. Configuring an NFSv4-only server

Describe the issue:
By default, rpc.mountd listens on 20048/tcp and 20048/udp (determinted by looking up mountd in /etc/services.

But NFSv4 does not use the MOUNT protcol, so these listeners are superfluous.

The docs should describe how to disable the listeners.

Suggestions for improvement:
After step 3, insert:

Configure rpc.mountd to not listen for NFSv3 MOUNT requests. Create /etc/systemd/system/nfs-mountd.service.d/v4only.conf:

[Service]
ExecStart=
ExecStart=/usr/sbin/rpc.mountd --no-tcp --no-udp

... then run systemctl daemon-reload && systemctl restart nfs-mountd.