network problems

[Matthias Leopold <matthias.leopold@meduniwien.ac.at>]

hi,

today i set up my first kvm guest, a centos 7 machine on a centos 6 kvm 
host. there are already 3 guests (centos 6) running (not set up by me). 
as far as i can see the setup is "the same", problem is as soon as i 
start the network in the guest the host physical interface goes down: 
"e1000e: eth0 NIC Link is Down". i'm using bridged networking, network 
driver in the guest is virtio. when i use "e1000" driver in the guest 
already starting the guest brings the host interface down. what could be 
wrong?

network on the kvm host is maybe a bit special as there are 3 physical 
interfaces altogether, one of them consists of two bonded SFP 
interfaces. the 3 "old" kvm guests use these interfaces in bridge mode 
with no problems. but they are centos 6, the new one is centos 7... is 
there a difference?

dmesg says:

device vnet9 entered promiscuous mode
br0: port 5(vnet9) entering forwarding state
vnet9: no IPv6 routers present
kvm: 11206: cpu0 disabled perfctr wrmsr: 0xc2 data 0xffff
e1000e: eth0 NIC Link is Down
br0: port 1(eth0) entering disabled state
br0: port 5(vnet9) entering disabled state
device vnet9 left promiscuous mode
...

guest network configuration

     <interface type='bridge'>
       <mac address='52:54:00:67:36:89'/>
       <source bridge='br0'/>
       <model type='virtio'/>
       <address type='pci' domain='0x0000' bus='0x00' slot='0x03' 
function='0x0'/>
     </interface>

thx
matthias

-- 
Matthias Leopold
IT Systems & Communications
Medizinische Universität Wien
Spitalgasse 23 / BT 88 /Ebene 00
A-1090 Wien
Tel: +43 1 40160-21241
Fax: +43 1 40160-921200