Simple Glassfish Cluster setup with session replication

I am trying to set up a two instance Glassfish cluster with session replication enabled between the two instances.

The eventual plan is to run Liferay portal on the cluster, but for now even the clusterjsp application does not persist session across the instances.

I have made sure that the application is deployed with availability enabled and confirmed that the option is still set for the application. I have also confirmed that the tag is present in the web.xml file.

I have tested to ensure multicast is working by running asadmin validate-multicast on both instances and they are able to communicate with each other. Both hosts are on the same subnet.

Are there any other steps that I am missing? What else could be preventing the sample application from seeing session data on another instance?

I appreciate any advice. Thanks!