11.1 Can you have Multiple IP addresses on one interface?

HP ServiceGuard allows you to configure multiple IP addresses on one
interface.

First, all primary network interfaces must have "stationary" IP addresses
"ifconfig"ed on them.  Say for example, you have a system with 2 ethernet
interfaces (one primary and one for backup) and 2 FDDI interfaces (one
primary and one backup) and they are interfaces lan0, lan1, lan2 and lan3
respectively.   Your /etc/rc.config.d/netconf file would have lan0 having
an IP address/subnet, etc (say 15.13.169.15) and lan2 would have  an IP
address/subnet, etc (192.6.144.15)

lan1 and lan3 would not be specified in the netconf file as they will not
initially have any IP addresses on them.

ServiceGuard has a "cmmodnet" command which will ADD IP addresses to existing
interfaces.  For example, to add a "Package IP" address to the ethernet
lan you would:

cmmodnet -a -i 15.13.169.16 15.13.143

Where -a is add -i 15.13.169.16 is the IP address to add and 15.13.143 is the
subnet where to add it.  The cmmodnet command (via the ioctl()s) then figures
out that the SUBNET is currently on lan0 and magically you have 2 ip addresses
on the same SUBNET.  Both going through lan0.

This feature is only currently available through the ServiceGuard product.