Allow IP address as URLs

Our squid server has a whitelist of approved IP addresses, and blocks
everything not on the list. Unauthorized site access generates an error
page which doubles a a request form, which can be submitted to request
access to that site. Ip addresses added to the list do not seem to work
when added to the whitelist in the same way as domains are (probably
because lookups fail when squid is reloaded). My workaround has been to
add a dns entry, but this is clumsy and tedious. How can I add specific
IP addresses to the whitelist and have them be treated the same as a
domain like "www.yahoo.com"?

example:

#begin whitelist
www.yahoo.com
www.mapquest.com
209.154.26.104 <---this one won't work

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-linux_lad