Why is the system sending multicast querie, "IP 0.0.0.0 > all-systems.mcast.net: igmp query v2" on a bridge device?

Issue

• Why is the system sending multicast querie, "IP 0.0.0.0 > all-systems.mcast.net: igmp query v2" on a bridge device?

# uname -r
2.6.32-358.el6.x86_64
# tcpdump -i br0 host 0.0.0.0
tcpdump: verbose output suppressed, use -v or -vv for full protocol decode
listening on br0, link-type EN10MB (Ethernet), capture size 65535 bytes
14:24:53.913488 IP 0.0.0.0 > all-systems.mcast.net: igmp query v2
14:26:58.913502 IP 0.0.0.0 > all-systems.mcast.net: igmp query v2
14:29:03.913497 IP 0.0.0.0 > all-systems.mcast.net: igmp query v2
14:31:08.913517 IP 0.0.0.0 > all-systems.mcast.net: igmp query v2
^C
4 packets captured
4 packets received by filter
0 packets dropped by kernel
# cat /sys/devices/virtual/net/br0/bridge/multicast_snooping 
1
# cat /sys/devices/virtual/net/br0/bridge/multicast_query_interval 
12498