[CentOS-virt] kvm: centos 7 guest on centos 6 host network problems

Mon May 23 14:08:57 UTC 2016
Matthias Leopold <matthias at leopold.priv.at>

Am 2016-05-23 um 12:50 schrieb Matthias Leopold:
> 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?

all this was caused by switch configuration in our network, no relation 
to kvm...