Enhancements in Release F.02.02

Operation and Enhancements for Multimedia Traffic Control (IGMP)

unnecessary multicast traffic from that group to the former IGMP client. This improves performance by reducing the amount of multicast traffic going through the port to the IGMP client after the client leaves a multicast group. IGMP in the Series 2500 switches automatically uses this Fast-Leave feature.

Automatic Fast-Leave Operation. If a Series 2500 switch port is :a.Connected to only one end nodeb.The end node currently belongs to a multicast group; i.e. is an IGMP clientc.The end node subsequently leaves the multicast group

Then the switch does not need to wait for the Querier status update interval, but instead immediately removes the IGMP client from its IGMP table and ceases transmitting IGMP traffic to the client. (If the switch detects multiple end nodes on the port, automatic Fast-Leave does not activate— regardless of whether one or more of these end nodes are IGMP clients.)

In the next figure, automatic Fast-Leave operates on the switch ports for IGMP clients "3A" and "5B", but not on the switch port for IGMP clients "7A" and 7B, Server "7C", and printer "7D".

Fast-Leave IGMP automatically operates on the ports connected to IGMP clients 3A and 5A, but does not operate on the port connected to Switch 7X because the Series 2500 switch detects multiple end nodes on that port.

Fast-Leave IGMP activates on these two ports.

Routing

Switch

Acting as

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3A

 

 

 

 

 

5A

 

 

 

 

 

 

 

7A

 

 

 

 

 

 

 

 

7B

 

 

7C

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Switch 7X

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Printer

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

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7D

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Series 2500 Switch

Fast-Leave IGMP does not activate on this port.

Figure 105. Example of Automatic Fast-Leave IGMP Criteria

When client "3A" running IGMP is ready to leave the multicast group, it transmits a Leave Group message. Because the Series 2500 switch knows that there is only one end node on port 3, it removes the client from its IGMP table and halts multicast traffic (for that group) to port 3. If the switch is not the Querier, it does not wait for the actual Querier to verify that there are no other group members on port 3. If the switch itself is the Querier, it does not query port 3 for the presence of other group members.

Note that Fast-Leave operation does not distinguish between end nodes on the same port that belong to different VLANs. Thus, for example, even if all of the devices on port 7 in figure 105 belong to different VLANs, Fast-Leave does not operate on port 7.

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