Explanation of igmp fast leave – Allied Telesis AR400 User Manual
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IGMP fast leave > Explanation of IGMP fast leave
Imagine that client 2 on switch 3 sends a Membership Report to join the group 224.12.13.14.
The Snooper, switch 3, adds this to its the IGMP snooping table. When the same client then
sends a Leave message, the IGMP Querier responds with a Membership Query and waits for
a configured time for a response.
The next sections describe in detail the differences between having Fast Leave disabled and
enabled, but in summary:
z
Without Fast Leave, the IGMP Snooper waits the same length of time as the Querier, then
expires the entry if there was no response.
z
With Fast Leave, the IGMP Snooper expires the entry as soon as it sees the Leave message
from the client. By the time the Querier sends the Membership Query, the Snooper will
have already expired the entry and therefore stopped sending the stream to the client.