We want to allow specific IPs to access a link on my web application and block other

Hi, 

You should be able to do it via the IP address exceptions if you really want to, but you'll probably find that this will be much easier (and better) using an iRule (such as this one from Kevin; https://community.f5.com/t5/technical-forum/irule-for-ip-whitelist-on-specific-url/td-p/213513) or using a Local Traffic Policy. 

Although ASM can track and block IP's, in general it is not geared towards filtering based on IP's. Any particular reason why you want to do it via there?