Public bug reported:
After configuring 2 identical servers with KVM and then trying to
migrate an image using bridged networking from one to the other, the
guest loses network connectivity after the migration completes.
A tcpdump shows the bridged network is passing packets /from/ the guest
(a test ping run in the guest via the VNC console) and reply packets are
received and bridged back onto the guest network interface without the
guest seeing the packet (i.e. packets come from vnet0, sent out on br0,
reply comes back from br0, is forwarded onto vnet0 but the guest never
sees the reply).
tcpdump -n -i vnet0
18:19:47.072378 IP 192.168.35.49 > 192.168.35.4: ICMP echo request, id 512, seq
2816, length 40
This is the echo packet sent by the guest
18:19:47.073119 IP 192.168.35.4 > 192.168.35.49: ICMP echo reply, id 512, seq
2816, length 40
This is the reply coming back except the actual guest does not ever see the
reply.
# lsb_release -rd
Description: Ubuntu 10.04.1 LTS
Release: 10.04
The packet forwarding seems to go amiss on the bridge or in qemu or
libvirt - there are a number of posts online with people finding similar
problems but nothing ever seems to answer why or how to fix it that I've
found.
brctl show
# brctl show
bridge name bridge id STP enabled interfaces
br0 8000.001517c8ef5e no eth1
eth2
vnet0
brctl showstp br0
br0
bridge id 8000.001517c8ef5e
designated root 8000.001517c8ef5e
root port 0 path cost 0
max age 20.00 bridge max age 20.00
hello time 2.00 bridge hello time 2.00
forward delay 0.00 bridge forward delay 0.00
ageing time 300.00
hello timer 1.64 tcn timer 0.00
topology change timer 0.00 gc timer 0.64
flags
eth1 (1)
port id 8001 state disabled
designated root 8000.001517c8ef5e path cost 100
designated bridge 8000.001517c8ef5e message age timer 0.00
designated port 8001 forward delay timer 0.00
designated cost 0 hold timer 0.00
flags
eth2 (2)
port id 8002 state forwarding
designated root 8000.001517c8ef5e path cost 4
designated bridge 8000.001517c8ef5e message age timer 0.00
designated port 8002 forward delay timer 0.00
designated cost 0 hold timer 0.64
flags
vnet0 (3) <-- the guest nic
port id 8003 state forwarding
designated root 8000.001517c8ef5e path cost 100
designated bridge 8000.001517c8ef5e message age timer 0.00
designated port 8003 forward delay timer 0.00
designated cost 0 hold timer 0.64
flags
** Affects: libvirt (Ubuntu)
Importance: Undecided
Status: New
** Tags: bridge libvirt migrate
--
Live Migration Guest Network Stops Responding
https://bugs.launchpad.net/bugs/612671
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