[Bridge] weird question ? kvm virtual network and bunch of bridges

[Radim Roska]

Hello,

I have this very uncommon situation :). My diploma thesis will probably be
playing with linux kernel in various networks. Currently I have little free
time and limited computer resources -> only one laptop :). But I would like
to do some profiling of kernel particularly of bridging part. For that i
need network.

So i have 2 virtual machines VPC1 and VPC2 (running debian)

HOST - VPC1 - VPC2

VPC1 should act as bridge.
HOST: tap0 interface
VPC1:
eth0 ~ tap1 on host
eth1 ~ tap2 on host
VPC2:
eth0 ~ tap3 on host

how to connect it? :) Well tap0 - tap1 is in br0 on host and tap2 + tap3 is
on br1.

VPC1 than has eth0 and eth1 in bridge also :).

I know..it looks strange..but i thought its simplest :).

But:

1) although VPC2 is connected through br1 that has connection only with
tap2=eth1 on VPC1..I can ping anything even when VPC1 has all interfaces
down

2) i dont see any loop in my "network" but anyway once i turn on br0
without stp on VPC1, i got quite a serious perf problem - little storm i
guess:).
starting stp solves storm but disables eth0
[ 3839.200640] br0: starting userspace STP failed, starting kernel STP
[ 3839.201388] br0: topology change detected, sending tcn bpdu
[ 3839.202117] br0: port 2(eth0) entering blocking state

i does not matter if i have stp on HOST's br0/br1

If someone would have time to help me with that I'll be very happy :). Its
possible Im trying approach that is doomed to fail because i dont
know/understsand something.

Cheers,
Radim
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