To prevent this you alias the 10.1.1.1 address (cluster address as it is called) on the loopback adapter of the www1 and www2 servers and trick them into to thinking that 10.1.1.1 is a valid address ...

Unix sysadmins routinely use the “ifconfig -a” command to list network parameters associated with their systems. In particular, they use this command to determine the IP address, netmask and broadcast ...