Use IP Failover IPs for a domain (including sub-domains)

Ok, so I have 3 IP failover IP’s, along with my main server’s IP

I’m hosting three websites, and I want to use 1 fail-over IP for each domain (including any subdomains), how would I do that?

I have the three fail-over IP’s configured as eth0:1, eth0:2 and eth0:3