Virtual machines cannot communicate over network bridges

Issue

• KVM or RHEV virtual machines cannot communicate over network bridges
• We have two RHEL6.5 hosts with a KVM guest on each. The second NIC with addresses in the 192.168.1.x IP range. The host machines have a bridge interface also in this range. The guests use a NIC configured to use the bridge as source and model is virtio. The KVM guests cannot ping each other, but can ping the host on which they reside only. The hosts can ping all four addresses: the two hosts and the two KVM guests.
• When we startup service avahi-daemon on the RHEL guest, after a while when we ping the ip address of the guest, we will meet the data lost issue.
• When our Windows VMs start IP Multicast, they become unreachable on the network.