There is another way of generating aliases that may be helpful in certain circumstances. Sometimes we want to create an alias for a website; however, that website may use multiple IP addresses (for example, Amazon uses six different IP addresses as of this writing). Rather than find out what these IP addresses are an input them manually, we can do this much more easily in pfSense.

To create an alias for a website, navigate to Diagnostics | DNS Lookup. On the DNS Lookup page, enter the hostname in the Hostname field and click on the Lookup button. When the results of the lookup are returned, there should be a button next to the Lookup button (before the Results section) labeled Add Alias. Click on the button, and an alias should be created, with any dots in the hostname converted to underscores (for example, if you did a DNS lookup on www.amazon.com, the corresponding alias would be amazon_com). Navigate back to Firewall | Aliases, and the newly created alias should be there.

The advantage of this method of creating an alias is that a DNS lookup should be effective in returning a list of valid IP addresses for a site, at least in the moment. A rule created based on such an alias should be effective, at least immediately after the DNS lookup was performed. But for popular websites, it may not be effective a day later, or even a few hours later, as such websites frequently add new IP addresses to the pool of addresses they use.