In the Redhat EL6 virtualization guide ( http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualiza... ) I read this:

#

Configure iptables Configure iptables to allow all traffic to be forwarded across the bridge.

# iptables -I FORWARD -m physdev --physdev-is-bridged -j ACCEPT # service iptables save # service iptables restart

Disable iptables on bridges Alternatively, prevent bridged traffic from being processed by iptables rules. In /etc/sysctl.conf append the following lines:

net.bridge.bridge-nf-call-ip6tables = 0 net.bridge.bridge-nf-call-iptables = 0 net.bridge.bridge-nf-call-arptables = 0

Reload the kernel parameters configured with sysctl.

# sysctl -p /etc/sysctl.conf

However, later in the same guide ( http://docs.redhat.com/docs/en-US/Red_Hat_Enterprise_Linux/6/html/Virtualiza... ) I read this:

* Enabling IP forwarding (net.ipv4.ip_forward = 1) is also required for shared bridges and the default bridge. Note that installing libvirt enables this variable so it will be enabled when the virtualization packages are installed unless it was manually disabled.

Note Note that enabling IP forwarding is not required for physical bridge devices. When a guest is connected through a physical bridge, traffic only operates at a level that does not require IP configuration such as IP forwarding.

Which leaves me a little confused. Is this talking about some form of network device other than the installed NIC? How is this information integrated with the requirement given in section 10.3? Can someone explain to me how these two sections relate to one another?

A second difficulty I encounter is that the first vm guest that I created does not seem to have any interface configuration file for etho in /etc/sysconfig/network-scripts. In fact, I see no ifcfg-x files at all. Am I supposed to create these by hand or have I somehow missed a configuration step in virt-manager?