Ganglia's gmond multicast traffic across kvm/qemu vnet0 bridge
From Use-Author-Supplied-Address-Header@@110:110/2002 to All on Fri Dec 27 04:45:01 2013
Has anyone come across this before?
I am running Ganglia's gmond daemon on a KVM guest and using multicast
as with the default configuration for gmond on all hosts to
communicate with each other and with the central gmetad. This all
works nicely on bare metal hosts, just the kvm guest was not
communicating via multicast. I found the following,
(1) 'tcpdump -i eth0 dst 184.108.40.206' on the guest only sees multicast traffic created by gmond running on that guest.
(2) 'tcpdump -i vnet0 dst 220.127.116.11' on the guest's bare metal host
also only sees multicast traffic created by the gmond running on its
(3) 'tcpdump -i br123 dst 18.104.22.168' on the guest's bare metal host
sees all the multicast traffic from all the other gmonds on our LAN
but none from its guest. br123 is the bridge device setup for 123
tagged packets on our 802.1Q VLAN. At the br123 interface stage the
packets are untagged so I presume this is not a VLAN problem.
Using virt-manager GUI for the guest's setup I have for the virtual NIC,
before the multicast traffic would be routed beyond the br123 device
on the host system and onto the LAN. I also found that trying to repeat
the process with a second VLAN also resulted in a system hang. A routing
: I also discovered that re-writing 2 to these pseudo files results in a
: total system freeze!
I noticed that the 'total system freeze' was not quite that. A 'top'
session running the console continued to run.
(PP IT Support)
Ps. The email address in the header is just a spam-trap.
Tom Crane, Dept. Physics, Royal Holloway, University of London, Egham Hill, Egham, Surrey, TW20 0EX, England.
Email: T dot Crane at rhul dot ac dot uk