Re: [Qemu-discuss] Guest fails to reconnect after host network goes down

[Tony Su]

Consider whether you're talking about layer 2  or layer 3 network
connectivity (test).
If this is a Workgroup, consider whether you have a Browse Master issue.
Consider whether your issue is a name resolution issue.
I assume the connection is bridged? Try NAT if it doesn't make a diff to you.

Tony

On Mon, Aug 24, 2015 at 7:29 AM, Vlad Yasevich <address@hidden> wrote:
> On 08/23/2015 07:31 AM, Davide Baldini wrote:
>> Thanks Vlad,
>>
> .. snip..
>>
>> As far as I notice, there are no differences shown by `ifconfig`.
>> The fact is, that all guests drop the network after a cable is unplugged and 
>> then
>> replugged, while the host's network keeps functioning.
>
> What do you mean by "drop network"?   Is the link going down in the guest?  Is
> the guest losing IP address?  Is the guest simply stops being reachable?
>
> Are there any firewall rules on the host?
>
> Thanks
> -vlad
>
>>
>> Where else can I look?
>>
>> -- Davide
>>
>> On 08/19/2015 08:02 PM, Vlad Yasevich wrote:
>>> On 08/16/2015 12:55 PM, Davide Baldini wrote:
>>>> When I unplug the ethernet cable from the physical host, guest fails to 
>>>> reconnect; host
>>>> does reconnect.
>>>
>>> What do you mean by 'reconnect'?  Unplugging the cable for the nic on the 
>>> physical host
>>> does not really disconnect the guest from the network.  According to the 
>>> configuration
>>> your provided, the guest is still connected to the bridge on the host and 
>>> can still
>>> communicate with other guests on the same host.
>>>
>>> Once the host network is plugged back in, the bridge should start 
>>> forwarding packets
>>> back to the guest.
>>>
>>>>
>>>> A very simple configuration here, with an almost default Debian 7 on both 
>>>> host and guest:
>>>>
>>>> -- ON HOST:
>>>>
>>>> /etc/network/interfaces
>>>>
>>>>    auto lo
>>>>    iface lo inet loopback
>>>>
>>>>    auto br0
>>>>    iface br0 inet dhcp
>>>>        bridge_ports    eth1
>>>>        bridge_stp      off
>>>>        bridge_maxwait  0
>>>>        bridge_fd       0
>>>>
>>>>
>>>> -- ON GUEST:
>>>>
>>>> /etc/network/interfaces
>>>>
>>>>    auto eth0
>>>>    allow-hotplug eth0
>>>>    iface eth0 inet static
>>>>        address 192.168.1.109
>>>>        netmask 255.255.255.0
>>>>        network 192.168.1.0
>>>>        broadcast 192.168.1.255
>>>>        gateway 192.168.1.1
>>>>        dns-nameservers 192.168.1.1
>>>>
>>>>
>>>> QEMU is started as:
>>>>
>>>> /usr/local/bin/qemu-system-x86_64 -hda /media/raid1/qemu-109 -m 8G -smp 4 
>>>> -enable-kvm
>>>> -netdev bridge,id=br109 -device 
>>>> virtio-net-pci,netdev=br109,id=nic0,mac=00:00:00:00:01:09
>>>> -k it -daemonize
>>>>
>>>> QEMU emulator version 2.3.0
>>>>
>>>> Nothing appears on dmesg. Any hints?
>>>
>>> Make sure that the bridge on the host is formed correctly after the cable 
>>> has been plugged
>>> back in.
>>>
>>> -vlad
>>>
>>>>
>>>> -- Davide
>>>>
>>>
>>
>
>