Thanks for the head up ! I suspected to be a problem on the client
side, specifically with the LinBox firewall rules... who knows maybe
there should be a direct forwarding for the ICMP and GRE packets
leaving his box and crossing the rules of his firewall instead of them
I'll talk this aspects of the matter and I'll come back with more info
regarding the case solving or ditching in despair.
kosson at gmail dot com