Hi,

i’m rather new to kvm. now i set up a CentOS 7 guest on a CentOS 6 kvm host.

when i try to use bridged networking in the CentOS7 guest this works for the interface that uses eth1/br1 on the host. when i try to use a second interface in the guest with eth0/br0 on the host this brings the host interface down as soon as i do ip configuration in the guest (so it seems). eth0 shall have the default route in host and guest. three other CentOS 6 guests (not set up by me) use both interfaces in bridged mode with no problems.

both interfaces on the host are intel cards (e1000e). driver in the kvm guest configuration is “virtio”.

dmesg on the kvm host (CentOS 6) says:

device vnet9 entered promiscuous mode br0: port 5(vnet9) entering forwarding state device vnet10 entered promiscuous mode br1: port 5(vnet10) entering forwarding state vnet10: no IPv6 routers present vnet9: no IPv6 routers present kvm: 17778: cpu0 disabled perfctr wrmsr: 0xc2 data 0xffff e1000e: eth0 NIC Link is Down
…

ethtool -k output differs in “rx-vlan-filter” (off for eth0)
CentOS 6 kernel is 2.6.32-573.22.1.el6.x86_64

what could be wrong?

thx matthias