Hi,

I've a KVM system upon which I'm running a network bridge directly between all VM's and a bond0 (eth0, eth1) on the host OS. As such, all machines are presented on the same subnet, available outside of the box. The bond is doing mode 1 active / passive, with an arp_ip_target set to the default gateway, which has caused some issues in itself, but I can't see the bond configs mattering here myself.

I'm seeing odd things most times when I stop and start a guest on the platform, in that on the host I lose network connectivity (icmp, ssh) for about 30 seconds. I don't lose connectivity on the other already running VM's though... they can always ping the default GW, but the host can't. I say "about 30 seconds" but from some tests it actually seems to be 28 seconds usually (or at least, I lose 28 pings...) and I'm wondering if this somehow relates to the bridge config.

I'm not running STP on the bridge at all, and the forwarding delay is set to 1 second, path cost on the bond0 lowered to 10 and port priority of bond0 also lowered to 1. As such I don't think that the bridge should ever be able to think that bond0 is not connected just fine (as continued guest connectivity implies) yet the IP of the host, which is on the bridge device (... could that matter?? ) becomes unreachable.

I'm fairly sure it's about the bridged networking, but at the same time as this happens when a VM is started there are clearly loads of other things also happening so maybe I'm way off the mark.

Lack of connectivity:

# ping 10.20.11.254                                          
PING 10.20.11.254 (10.20.11.254) 56(84) bytes of data.                          
64 bytes from 10.20.11.254: icmp_seq=1 ttl=255 time=0.921 ms                    
64 bytes from 10.20.11.254: icmp_seq=2 ttl=255 time=0.541 ms                    
type=1700 audit(1293462808.589:325): dev=vnet6 prom=256 old_prom=0 auid=42949672
95 ses=4294967295                                                               
type=1700 audit(1293462808.604:326): dev=vnet7 prom=256 old_prom=0 auid=42949672
95 ses=4294967295                                                               
type=1700 audit(1293462808.618:327): dev=vnet8 prom=256 old_prom=0 auid=42949672
95 ses=4294967295                                                               
kvm: 14116: cpu0 unimplemented perfctr wrmsr: 0x186 data 0x130079               
kvm: 14116: cpu0 unimplemented perfctr wrmsr: 0xc1 data 0xffdd694a              
kvm: 14116: cpu0 unimplemented perfctr wrmsr: 0x186 data 0x530079               
64 bytes from 10.20.11.254: icmp_seq=30 ttl=255 time=0.514 ms                   
64 bytes from 10.20.11.254: icmp_seq=31 ttl=255 time=0.551 ms                   
64 bytes from 10.20.11.254: icmp_seq=32 ttl=255 time=0.437 ms                   
64 bytes from 10.20.11.254: icmp_seq=33 ttl=255 time=0.392 ms 

brctl output of relevant bridge:

# brctl showstp brdev
brdev
 bridge id      8000.b2e1378d1396
 designated root    8000.b2e1378d1396
 root port         0            path cost          0
 max age          19.99         bridge max age        19.99
 hello time        1.99         bridge hello time      1.99
 forward delay         0.99         bridge forward delay       0.99
 ageing time         299.95
 hello timer           0.50         tcn timer          0.00
 topology change timer     0.00         gc timer           0.04
 flags          


vnet5 (3)
 port id        8003            state            forwarding
 designated root    8000.b2e1378d1396   path cost        100
 designated bridge  8000.b2e1378d1396   message age timer      0.00
 designated port    8003            forward delay timer    0.00
 designated cost       0            hold timer         0.00
 flags          

vnet0 (2)
 port id        8002            state            forwarding
 designated root    8000.b2e1378d1396   path cost        100
 designated bridge  8000.b2e1378d1396   message age timer      0.00
 designated port    8002            forward delay timer    0.00
 designated cost       0            hold timer         0.00
 flags          

bond0 (1)
 port id        0001            state            forwarding
 designated root    8000.b2e1378d1396   path cost         10
 designated bridge  8000.b2e1378d1396   message age timer      0.00
 designated port    0001            forward delay timer    0.00
 designated cost       0            hold timer         0.00
 flags          

I do see the new port listed as learning, but in line with the forward delay, only for 1 or 2 seconds when polling the brctl output on a loop.

All pointers, tips or stabs in the dark appreciated.