[CentOS-virt] KVM integrated network (user mode) dying after inactivity
timo at riscworks.net
Wed Jun 4 18:40:24 UTC 2014
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I searched the web for bug reports regarding this phenomenon I see on
*multiple* machines of a customer, however, I didn't find an exact
fit. So, I'd like to ask here whether anyone else has run into this.
I have multiple CentOS 6 machines running using KVM to virtualize a
bunch of machines on them (LVM-based).
Software releases as following:
[root at fe00 ~]# rpm -qa|egrep '(virt|kvm)'
[root at fe00 ~]# uname -r
The VMs (here: two) have the "default" connection provided by KVM
(heading to the internet) as well as a bridged interface to connect to
a high performance backbone, where sensitive data is kept and
bandwidth is an issue (or better, not :), on a second interface within
[root at fe00 ~]# brctl show
bridge name bridge id STP enabled interfaces
br1 8000.001b21xxxxxx yes eth1
virbr0 8000.525400xxxxxx yes virbr0-nic
br1 is the interface connected to the backbone, virbr0 KVM's user mode
After some time of inactivity on the virbr0 interface, from *within*
the VMs connection is *lost*. The interface(s) lose their IP; running
dhclient(8) is not of any use.
To get the machine back onto track, ``service libvirtd restart'' has
to be issued: Vanished iptables rules show up again. (This, in
contrast to an Ubuntu document , fixes it without shutting the
VM(s) down.) Starting dhclient(8) within the VMs gets connectivity back.
Just out of curiosity I let one of the VMs cause some ICMP traffic now
and then hit the interface -- ``ping -i 10 some.nice.host'' is
sufficient to keep that interface alive.
The virbr0-headed interfaces are almost only being used to get updates
etc -- management and load-balanced services are being served by the
Is this a bug or a feature?
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