3Com Switch 7750 Configuration Guide Guide

410 CHAPTER 43: IGMP CONFIGURATION
To reduce the workload of configuration and management without affecting the
multicast connection of leaf networks, you can configure an IGMP Proxy in a Layer
3 switch in the leaf network (Switch B in the figure). The Layer 3 switch will then
forward IGMP join or IGMP leave messages sent by the connected hosts. After the
configuration of IGMP Proxy, the leaf switch is no longer a PIM neighbor but a
host for the external network. Only when the Layer 3 switch has directly
connected members, can it receive the multicast data of corresponding groups.
Figure 96 Diagram for IGMP Proxy
Figure 96 is an IGMP Proxy diagram for a leaf network.
Configure Switch B as follows:
■ Enable multicast routing on VLAN interface 1 and VLAN interface 2, and then
configure the PIM protocol on it. And configure the IGMP protocol on
VLAN-interface 1 at the same time.
■ On VLAN interface 2, configure VLAN interface 1 as the outbound IGMP Proxy
interface to external networks. You must enable the IGMP protocol on the
interface first, and then configure the igmp proxy command.
Configure Switch A as follows:
■ Enable multicast routing and configure the IGMP protocol on VLAN interface 1.
■ Configure the pim neighbor-policy command to filter PIM neighbors in the
network segment 33.33.33.0/24. That is, Switch A does not consider Switch B
as its PIM neighbor.
In this case, when Switch B of leaf network receives from VLAN interface 2 an
IGMP join or IGMP leave message sent by the host, it will change the source
address of the IGMP information to the address of VLAN interface 1: 33.33.33.2
and send the information to VLAN interface 1 of Switch A. For Switch A, this
works as if there is a host directly connected to VLAN interface 1.
Exterior network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave information
Exterior network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave information
Host
Exterior network
Leaf network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave message
VLAN-interface 1
VLAN-interface 2
General group/
Group-Specific Query message
IGMP
join / leave
message
VLAN-interface 1
33.33.33.1
33.33.33.2
22.22.22.1
Switch A
Switch B
Host
Exterior network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave information
Exterior network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave information
Exterior network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave information
Exterior network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave information
Host
Exterior network
Leaf network
General group/ Group -Specific Query information
Host
Exterior network
Leaf network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave message
General group/
Group-Specific Query message
IGMP
join / leave
message
33.33.33.1
33.33.33.2
22.22.22.1
Switch A
Switch B
Host
Exterior network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave information
Exterior network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave information
Exterior network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave information
Exterior network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave information
Host
Exterior network
Leaf network
General group/ Group -Specific Query information
Host
Exterior network
Leaf network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave message
VLAN-interface 1
VLAN-interface 2
General group/
Group-Specific Query message
IGMP
join / leave
message
VLAN-interface 1
33.33.33.1
33.33.33.2
22.22.22.1
Switch A
Switch B
Host
Exterior network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave information
Exterior network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave information
Exterior network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave information
Exterior network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave information
Host
Exterior network
Leaf network
General group/ Group -Specific Query information
Host
Exterior network
Leaf network
General group/ Group -Specific Query information
IGMP join/ IGMP
leave message
General group/
Group-Specific Query message
IGMP
join / leave
message
33.33.33.1
33.33.33.2
22.22.22.1
Switch A
Switch B
Host