I had a major HD failure and need to rebuild my host server and the virtual servers that resided on it. I am moving from CentOS 5.6 to CentOS 6.3. I am using the same configuration, as best as I can tell, that was working only hours ago on 5.6 but does not work on 6.3. My guest server can see network traffic on the bridged network device but I cannot seem to interact with it. Iptables turned off on both the host and guest makes no difference. *Host server settings that apply:* NetworkManager is off Network is on /etc/sysconfig/network NETWORKING=yes NETWORKING_IPV6=no HOSTNAME=host GATEWAY=192.168.4.1 /etc/resolv.conf search domain.com nameserver 68.87.xx.xx nameserver 68.87.xx.xx /etc/sysctl.conf net.ipv4.ip_forward = 1 net.bridge.bridge-nf-call-ip6tables = 0 net.bridge.bridge-nf-call-iptables = 0 net.bridge.bridge-nf-call-arptables = 0 /etc/sysconfig/network-scripts/ifcfg-em2 DEVICE=em2 NM_CONTROLLED=no BOOTPROTO=none HWADDR=... ONBOOT=yes HOTPLUG=no BRIDGE=br2 /etc/sysconfig/network-scripts/ifcfg-br2 DEVICE=br2 TYPE=Bridge BOOTPROTO=none ONBOOT=yes DELAY=0 /etc/sysconfig/network-scripts/ifcfg-em3 DEVICE=em3 NM_CONTROLLED=no BOOTPROTO=none HWADDR=... ONBOOT=yes HOTPLUG=no BRIDGE=br3 /etc/sysconfig/network-scripts/ifcfg-br3 DEVICE=br3 TYPE=Bridge BOOTPROTO=none ONBOOT=yes DELAY=0 On the host I connect to the network using a different nic ifcfg-em5. Which connects to the gateway server and the internet just fine. *The guest settings:* Virtual Network Interface Source Device: Host device vnet0 (Bridge 'br2') Device Model: virtio MAC Address: ... Virtual Network Interface Source Device: Host device vnet1 (Bridge 'br3') Device Model: virtio MAC Address: ... NetworkManager is off Network is on /etc/sysconfig/network NETWORKING=yes NETWORKING_IPV6=no HOSTNAME=host GATEWAY=192.168.4.1 /etc/resolv.conf search domain.com nameserver 68.87.xx.xx nameserver 68.87.xx.xx /etc/sysctl.conf net.ipv4.ip_forward = 1 net.bridge.bridge-nf-call-ip6tables = 0 net.bridge.bridge-nf-call-iptables = 0 net.bridge.bridge-nf-call-arptables = 0 /etc/sysconfig/network-scripts/ifcfg-eth0 DEVICE="eth0" BOOTPROTO="static" HWADDR=... NM_CONTROLLED="no" ONBOOT="yes" IPADDR=192.168.4.3 NETMASK=255.255.255.0 NETWORK=192.168.4.0 DNS1=68.87.XX.XX DNS2=68.87.XX.XX /etc/sysconfig/network-scripts/ifcfg-eth1 DEVICE="eth1" BOOTPROTO="static" HWADDR=... NM_CONTROLLED="no" ONBOOT="yes" IPADDR=192.168.6.1 NETMASK=255.255.255.0 NETWORK=192.168.6.0 #route Kernel IP routing table Destination Gateway Genmask Flags Metric Ref Use Iface 192.168.6.0 * 255.255.255.0 U 0 0 0 eth1 192.168.5.0 otherserver 255.255.255.0 UG 0 0 0 eth0 192.168.4.0 * 255.255.255.0 U 0 0 0 eth0 192.168.1.0 anotherserver 255.255.255.0 UG 0 0 0 eth0 link-local * 255.255.0.0 U 1002 0 0 eth0 link-local * 255.255.0.0 U 1003 0 0 eth1 default gatewayserver 0.0.0.0 UG 0 0 0 eth0 This is the most bizarre thing. I can see the nic traffic on the guest with a tcpdump but I cannot interact with the traffic. # traceroute 192.168.4.1 traceroute to 192.168.4.1 (192.168.4.1), 30 hops max, 60 byte packets 1 guestserver (192.168.4.3) 3000.636ms !H 3000.633ms !H 3000.628 ms !H Any fresh ideas and insights are greatly appreciated! Thanks!