1) What are keepalived's (physical/network) requirements? Does the two (or more) keepalived' nodes need to be connected to the same switch? (something related to broadcasting maybe).
2) Can keepalived nodes run on different networks, "internet" networks?
3) Is keepalived depend on the router? (as far as I understand, the virtual IP should point to the real router/switch that connects both nodes).
4) Is keepalived "service-independent"?
-> What is keepalived's involvement domain? IPs only? Or is it service/protocol oriented?
-> Does it deal ONLY with IP, or is it designed for HTTP for example?
-> In other words, can I use it for custom (network-based) app?
5) Have more than one failover server?
If the answer for question #4 is "yes", i.e it depends on the service type, then is there any general alternative? Preferably easy to install/configure :)
As alternative there is Heartbeat, the main difference is:
keepalived = make sure at least 1 server runs the VIP
heartbeat = make sure at maximum 1 server runs the VIP
Don't use keepalived and heartbeat. This is deprecated software.
Try pacemaker and corosync. It can broadcasts, multicast.