Source IP Hash load balancing question

Question

Hello,

I'm using a Virtual Server using TCP protocol and I'm using Source IP Hash for the load balancing method. I'm using this maintain some persistence because I was having issue with the SSL Offloading and could not find a way to disable it. I'm running a Citrix protocol encapsulated inside of SSL and haven't fully debugged.

In any event, I have 4 real servers in place right now and the distribution is a little uneven. This is expected and not a big issue.

What I'd like to know is how does the formula work? It obviously uses the SourceIP and possibly the number of available Real Servers. I'm wondering what the impact would be if I added another Real Server.

Does anyone know what the formula is? I don't want to add another server without having a little more info so that I don't keep interrupting the poor mans persistence that I am using.

Cheers.

Chuck.

gschmitt · Answer

The traffic load is statically spread evenly across all real servers. However, sessions are not assigned according to how busy individual real servers are. This load balancing method provides some persistence because all sessions from the same source address always go to the same real server. However, the distribution is stateless, so if a real server is added or removed (or goes up or down) the distribution is changed and persistence could be lost.

http://docs.fortinet.com/...e-load-balance-521.pdf

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