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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.)
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.
Video
Server
Series 2500 Switch
Host "A1"
Outbound Multicast
Traffic from Video Server
for Group "A" on VLAN 3
Drop
Join Request
for group "A"
from Host A1
on VLAN 3
Host "A2"
Group "A" Multicast
Traffic for Host "A1"
No Join Request from
Host A2 on VLAN 3
No Group "A" Multicast
Traffic for Host "A2"
Forward