[SOLVED] kvm: lan freezes when starting vmachine with 2 net cards
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kvm: lan freezes when starting vmachine with 2 net cards
I'm testing kvm: a guest server with 2 network cards. When the guest starts the whole LAN freezes. If I start it with 1 net card it works with no problem.
Test: star vm - tcpdump - stop vm
tcpdump shows the same pocket received many many times
(example:
16:53:58.014920 STP 802.1d, Config, Flags [none], bridge-id 8001.00:1c:f9:fd:42:40.8001, length 42
16:53:58.014927 STP 802.1d, Config, Flags [none], bridge-id 8001.00:1c:f9:fd:42:40.8001, length 42
16:53:58.015261 STP 802.1d, Config, Flags [none], bridge-id 8001.00:1c:f9:fd:42:40.8001, length 42
...)
The message is not meaningfull. Every time a start the test I got a completely different message.
Some details:
-------------
brctl show:
Code:
bridge name bridge id STP enabled interfaces
bridge0 8000.00226489f2cb no eth3
qemutap0
bridge1 8000.00226489ec24 no eth4
qemutap1
Not sure from the info above, but you're either creating a loop or having duplicate IPs. I wouldn't expect a 'freeze' from the latter, but the former definitely will; the network isn't 'frozen', but flooded by packets from your loop (compare an open microphone before a speaker; the squeal from the loop blocks out all music). That would be consistent with your tcp dump.
Any chance of duplicate MAC-addresses? I've seen this sort of thing happen before, don't remember what it was, but it was definitely an invalid interface configuration.
eth0 - host interface
eth1 and eth2 - used in bond (bond0) for a direct connection with a twin server for DRBD redundancy
eth3 belong to bridge0
eth4 belong to bridge1
eth5 belong to bridge2
eth6 belong to bridge3
virtual net for virtual machine are qemutap0 and qemutap1, bound to bridge0 and bridge1
Those interfaces are setup by the script which starts the vm
I suppose there i something similar to a loop but note that if I startup the two qemutap interface without star the virtual machine no freeze happen.
I also think that during the freeze tcpdump record one broadcast message bouncing around ...
I note that:
- bond0 and its eth1 eth2 has the same mac address which is the real address of eth1. But I think it's ok.
- each bridge gets the mac address of the phisical interface eth* bound to it. I suppose is normat too.
- the two qemutap interfaces has their own mac address
- I've tried to start the virtual machine without setting a mac address from the command line, but the freeze is the same
As I'm not really that deep into this sort of thing, I cannot comment on these duplicate MAC addresses, but I would expect MAC addresses to be unique.
Just thinking out loud:
- Your packets indicate they are STP (Spanning Tree Protocol) packets. Config?
- Your btctl output shows STP is disabled on your bridges
- STP is supposed to prevent bridge loops
- Yet the behavior of your setup is that it does suffer bridge loops
Where do these STP packets come from, when STP is disabled?
Is there a way to enable STP on your bridges?
If yes, what's the effect?
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