IP alias - multiple IP subnets on one physical interface

http://www.openbsd.org/faq/faq6.html#Setup.aliases

and a firewall to control them with

http://www.openbsd.org/faq/faq6.html#PF

Not OpenBSD only, Linux with IP aliasing and IPtables will do the same.

btw. you have PHP misconfigured, it is spewing its error log

Warning: Missing argument 2 for polldaddy_show_rating_comments(), called in /var/sites/s/shkspr.mobi/public_html/blog/wp-includes/plugin.php on line 235 and defined in /var/sites/s/shkspr.mobi/public_html/blog/wp-content/plugins/polldaddy/rating.php on line 6