Enhancements in Release F.02.02

Operation and Enhancements for Multimedia Traffic Control (IGMP)

multicast packets to ports from which a join request for that group has not been received. (If the switch or router has not received any join requests for a given multicast group, it drops the traffic it receives for that group.)

Video

Server

Outbound Multicast Traffic from Video Server for Group "A" on VLAN 3

 

 

 

 

 

 

Join Request

 

Series 2500 Switch

 

 

for group "A"

 

 

 

Forward

 

 

 

 

 

from Host A1

 

 

 

 

 

Drop

 

on VLAN 3

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

No Join Request from Host A2 on VLAN 3

Host "A1"

Group "A" Multicast

Traffic for Host "A1"

Host "A2"

 

 

 

No Group "A" Multicast

 

 

Traffic for Host "A2"

Figure 104. Example of Data-Driven IGMP Operation

Thus, after you enable IGMP on a VLAN configured in the switch, it continually listens for IGMP messages and IP multicast traffic on all ports in the VLAN, and forwards IGMP traffic for a given multicast address only through the port(s) on that VLAN where an IGMP report (join request) for that address was received from an IGMP client device.

Note

IP multicast traffic groups are identified by IP addresses in the range of 224.0.0.0 to 239.255.255.255.

Incoming IGMP packets intended for reserved, or "well-known" multicast addresses automatically flood through all ports (except the port on which the packets entered the switch). For more on this topic, see “The Switch Excludes Well-Known or Reserved Multicast Addresses from IP Multicast Filtering” on page 216.

IGMP Operates With or Without IP Addressing

Formerly, IGMP operation on the Series 2500 switches required an IP address and subnet mask for each VLAN running IGMP. Beginning with release F.02.02, you can configure IGMP on VLANs that do not have IP addressing. The benefit of IGMP without IP addressing is a reduction in the number of IP addresses you have to use and configure. This can be significant in a network with a large number of VLANs. The limitation on IGMP without IP addressing is that the switch cannot become Querier on any VLANs for which it has no IP address—so the network administrator must ensure that another IGMP device will act as Querier and that an additional IGMP device is available as a backup Querier.

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