Thank you ruc. As you say, with tcpdump on the firewall we clearly see that the fierwall is waiting for the end of the submission from the sender IVE that stops after 20 packets, certainly waiting for an answer from the distant IVE ? So we are in a deadlock situation : - The firewall waits for the end of the message to process and transmit; - The IVE waits for something before sending the rest of the message It seems that neither on the FW nor the IVE we can change this behaviour. Ma questions are now : - Is this will definitly make it impossible to build the cluster ? - If the cluster can be setup, will it still as this behaviour is only link to the test tool ? - You can setup the cluster and as long as synchronization will not need to send big packets it will work fine ? Regards, ... View more