Hi:
First, I'm glad to hear that you've confirmed that replication is working when clustered instances are running on a single machine - I'm basing this on the following statement you make: "...SessionData is replicated when everything is done one one host "
That is good to know - and makes it more likely that the problem is in the interaction between your load balancer and the cluster instances. I don't have experience with the Alteon load balancer, so I hope someone else with that knowledge can step in and help you further.
For memory replication to work correctly, the load balancer should respect sticky round robin semantics - this is standard for web tier load balancers. And it should respect cookies (or url rewriting).
As for your question (below) about shared memory settings. This applies when you are using HADB and is not needed for memory replication which does not using shared memory.
I am doing this on a Debian - EtchBox.
Are these settings still required ? (*I think they where for 8.1 Release*)
echo 536870912 > /proc/sys/kernel/shmmax
echo 536870912 > /proc/sys/kernel/shmall
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