set igmp header-validation

This command enables header validation for IGMP messages. When header validation is enabled, IGMP Snooping checks:

The time-to-live (TTL) field in the IGMP header and drops packets where TTL is not equal to 1. The TTL field should always be set to 1 in the headers of IGMP reports and queries.
The presence of the router alert option (9404) in the IP packet header of the IGMPv2 message and drops packets that do not include this option.
The presence of the router alert option (9404) and ToS Byte = 0xC0 (Internet Control) in the IP packet header of IGMPv3 message and drops packets that do not include these options.