ANSWER:

You need to have a ASN. You can’t really announce less than a /25 network. There is no guarantee that any session will go over the same route, but most will likely use the same paths.

That is however not relevant for the application sessions, as the routers are not session aware – they simply forward packets regardless of states/types/flags.
Anycasting is used for all types of services.

The users will end up on the server (or loadbalancer) that holds the IP, it has nothing to do with which server it ends up at. If client 1.1.1.1 talks to server 2.2.2.2, client will always communicate with 2.2.2.2 regardless of how it was routed on the internet or intranet.

The router is not “server-state aware”, and it announces networks – not individual IP’s. It will not know or care if the server is able to respond, I think you are confusing it with a load balancer (like IPVS, HAproxy).

In case you’re not confusing it, then you need multiple transit providers that announce your network (or part of it, at least /25). If you are colocated, you can simply ask your providers to announce your networks. I think the function for announcing a customers ASN is by the AS-SET information, but I am a little unsure about that.

by 3molo from http://serverfault.com/questions/382533