
Chapter 20 IGMP
IES-1248-51V User’s Guide
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2 The multicast server sends traffic to the IES-1248-51V.
3 The IES-1248-51V manages all Join and Leave requests from Hosts 1, 2, and 3
downstream.
4 When the last leave request is received, the IES-1248-51V sends a Leave request
upstream to the multicast server to discontinue the traffic.
By managing multicast queries in this manner, the IES-1248-51V can present
itself as a single recipient to the multicast server. All downstream host traffic is
contained at the IES-1248-51V layer, thus freeing the multicast server for other
tasks.
20.2.2.1 VLAN Queries and IGMP Proxy
If you are using IGMP Proxy, you can use VLAN ID queries to direct multicast
traffic to specific downstream hosts. This allows you to limit which hosts receive a
multicast stream by directing a multicast stream to a specific VLAN group
For example, in the figure below the multicast server (MS) tags stream A with
VID= 1; that stream then only goes to the hosts in VLAN 1. Stream B is tagged
with VID 2 and so that stream only goes to the hosts in VLAN 2. This keeps the
multicast traffic segrated from the hosts that do not want it, thus reducing their
bandwidth overhead.
Figure 79 Example of Using Multicast with VLAN ID Queries
Note: See Section 20.6 on page 179 for details on configuring VLAN queries with
IGMP.
MS
VLAN 1 VLAN 2
VID=1 VID=2
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