Thank you for your answer. I'll explain more in detail the environment. We have two virtual machines. Each of them we have two instances of JBoss running (with different configurations of course). And one of the instances of one machine forms part of a cluster with other instance in the other machine. So, in the end, we have two clusters, lets call them Spain and Colombia (the real ones). Here is an example of the JSESSIONID of the Colombian cluster, the ones without eh two asterisks (so, this is an indicative of clustered JSESSIONID? ). Also is an example of a JSESSIONIDSSO: JSESSIONIDSSO=16D95E07D7FD37CC0D09BF5B726F3B20 JSESSIONID=2D52EA0E56A4330C145C44075E4316F9.Node2 We use the same pattern for defining the jvmRoute for both clusters: both have one called Node1 and other called Node2. In the Spain cluster, when the JSESSIONID works correctly, it is like this: JSESSIONIDSSO=EEEED918158A844B050B822E8835940F JSESSIONID=qjL2rvE2+Ly5+oWp7q0bTA**.Node1; And when it fails, it's like this JSESSIONID=.Node2 -> the first time you access JBoss JSESSIONID=.Node2.Node1 -> the second and subsequent times. 2 and 1 value varies depending of the server accessed. We use Apache mod_proxy_ajp, sorry, I told you wrong. The problem is we use sticky sessions, and the balancer uses the jvmRoute string to distinguish between one instance and the other (we have two virtual host and two balancers, for redirecting to Spain and Colombia respectively ). I read the TwoClustersInTheSameNetwork document in JBoss online docs, and yesterday we have applied a workaround explained there in another environment (that is a exact replica of this one). This was about setting emptySessionPath=false in the connector in jboss-web.deployer/server.xml file. The problem has not occurred since then... but I'm not very confident myself with this fix. About the tag, yes I've confirmed that in this cluster is not set, AND this problem does not occur. About JBoss, We use JBoss 4.3 EAP. Thank you! View the original post : http://www.jboss.org/index.html?module=bb&op=viewtopic&p=4240255#... Reply to the post : http://www.jboss.org/index.html?module=bb&op=posting&mode=reply&a...