Symptom
IGMP query with source IP address 0.0.0.0 triggers a querier
election process. As a consequence, port on which this packet is received is
marked as mrouter port for that VLAN.
3850#sh ip igmp snooping mrouter
Vlan ports
---- -----
100 Gi1/0/5(dynamic)
Conditions
This symptom is seen when IGMP query with source IP address
0.0.0.0 is received.
Workaround
Configure an ACL to block packets with source IP address 0.0.0.0
and apply it to relevant interfaces.
access-list 100 deny ip host 0.0.0.0 any
access-list 100 permit ip any any
int vlan 100
ip access-group 100 in
or
access-list 100 deny igmp any any host-query log-input
access-list 100 permit ip any any
int vlan 100
ip access-group 100 in
Further Problem Description
Per RFC 4541, IGMP query with source IP address
0.0.0.0 is used in special cases. When such query is received by a router, it
should not be used in the querier election process.
