Hi all, Playing around with Red Hat Clustering, it turns out I have a hughe multicast packet loss: (Centos 6.4 - x86_64 with all updates) omping 192.168.1.211 192.168.1.212 -c500 (node1) omping 192.168.1.212 192.168.1.211 -c500(node2) will give almost 50% loss! 192.168.1.211 : unicast, xmt/rcv/%loss = 500/500/0%, min/avg/max/std-dev = 0.330/0.610/0.789/0.064 192.168.1.211 : multicast, xmt/rcv/%loss = 500/268/46%, min/avg/max/std-dev = 0.416/0.635/0.921/0.066 192.168.1.212 : unicast, xmt/rcv/%loss = 500/500/0%, min/avg/max/std-dev = 0.388/0.653/0.863/0.069 192.168.1.212 : multicast, xmt/rcv/%loss = 500/263/47%, min/avg/max/std-dev = 0.396/0.670/1.080/0.074 OK, I am using simple hardware, but this hardware is virtually doing nothing... As mentioned on https://access.redhat.com/knowledge/sites/default/files/attachments/rhel_clu..., I set the txqueelen to 500, same result? I 'm still guessing whether this is an oVirt, virtio or Red Hat/Centos issue? Problems only happend after some time; that is 200 mo-pings shows everything is fine. Anyone? Winfried