Comment 21 for bug 584048

I'm also having this problem. Running 10.04 with KVM and Libvirt, starting VMs with "virsh start <domain>"

I've tested with OpenBSD 4.7 and Debian Lenny 5.0.5, both of them are having this issue.

I notice that networking with the bridge works fine at first for my guests, but after a while, the bridge stops functioning, and I can't reach it via SSH, nor can I ping/ssh out.

Also, when this happens, the ARP entry on the firewall I'm using to SSH to the guest changes from the Guest's MAC to the Host's MAC address.

On OpenBSD, if I run the /etc/netstart script to re-initialize the interface, the bridge starts functioning again, as if I restarted the VM, but quickly fails again (10-20 minutes). I have to reboot the Debian machine to get networking functioning again.

Here is my /etc/network/interfaces on the host:
# The loopback network interface
auto lo
iface lo inet loopback

# The primary network interface
auto eth0
iface eth0 inet dhcp

auto br0
iface br0 inet static
 address 192.168.8.166
 netmask 255.255.252.0
 network 192.168.8.0
 broadcast 192.168.11.255
 gateway 192.168.8.1
 bridge_ports eth1
 bridge_fd 9
 bridge_hello 2
 bridge_maxage 12
 bridge_stp off

And my /etc/libvirt/qemu/networks/autostart/default.xml:
<network>
  <name>default</name>
  <bridge name="virbr%d" />
  <forward/>
  <ip address="192.168.122.1" netmask="255.255.255.0">
    <dhcp>
      <range start="192.168.122.2" end="192.168.122.254" />
    </dhcp>
  </ip>
</network>