Login to WHM as user root. Then go to WHM > Plugins > ConfigServer Security & Firewall.
On the text box right side of the “Quick Allow” button, enter the IP address you need to whitelist. Then click on the “Quick Allow” button.
The Quick Deny option below can be used to block an IP address from accessing the server.
Quick Ignore allows you to ignore any IP address. This is the same as Quick ALLOW. The difference is if you whitelist an IP address using the Quick Allow option and if the IP fails some ModSecurity rules or makes several failed logins, it gets blocked. If you ignored an IP address, it will never get blocked by ModSecurity or lfd.