Some OS's has support for "virtual net interfaces", meaning that one computer gets many ip-addresses on the same physical ethernet interface. With Spinner this means that you easily can have many virtual server, with different IP numbers on the same computer.

On a Linux machine

For multiple IP numbers the Linux aproach which works best is with the dummy interface. First you recompile a recent kernel, including the possibiliy of modules. In the kernel, do not include the dummy interface. Next you do a "make modules", and a "make install-modules". After you have rebooted you can add extra ip numbers by doing (you can also add this to your /etc/rc.d/rc.local):
# Add dummy modules
######################################
/sbin/insmod -o dummy0 ./dummy.o
/sbin/insmod -o dummy1 ./dummy.o

# Add interface params, route arp addr
######################################
/sbin/ifconfig dummy0 www.click.es up
/sbin/route add www.click.es dummy0
/sbin/arp -s www.click.es 00:20:A9:0B:49:D5 pub

/sbin/ifconfig dummy1 www.ibercaja.es up
/sbin/route add www.ibercaja.es dummy1
/sbin/arp -s www.ibercaja.es 00:20:A9:0B:49:D5 pub
Note that the hardware address is YOUR ethernet hardware address. You can get it from the ifconfig eth0 output.

On a Solaris machine

ifconfig leY:X IP-ADDRESS broadcast BCAST netmask NETMASK up
Y is the number of the ethernet interface, X is a number between 1 and 255 (the virtual interface number).

On a FreeBSD machine

ifconfig le0 IP-ADDRESS alias netmask 0xffffffff

With an ifconfig that supports the alias option

 ifconfig le0 IP-ADDRESS alias 
Don't forget to add the names in you DNS configuration! See also Two Servers, One Interface.

If you know how to do this on other OS's, please send us a mail, telling us about it.