Networking Requirements

Figure 1. Example for Configuring IGMP Snooping with IGMP

As shown in Figure 1, there are three hosts, Host A, Host B and Host C, in the same network segment, which are multicast receivers. They are connected to the multicast source through the L3 switch and PIM network. The multicast source sends data to the multicast group 224.1.1.1.

In this scenario, the necessary requirement needed to be satisfied is that multicast traffic from the source is forwarded only to the member ports that have sent the IGMP Report messages.

For example, in above figure, assuming that only Host A has sent IGMP Report messages to join the multicast group or replied to a query message, the multicast traffic sent from the source device is expected to be forwarded only to port te-1/1/23, instead of being flooded to all ports of the same VLAN.

To achieve above network requirement, complete the following configurations on the Layer 3 Switch:

Enable PIM on all the VLAN interfaces (vlan2222 and vlan3333), configure IGMP on host-side VLAN interface (vlan2222).
Enable IGMP snooping on host VLAN (VLAN ID: 2222).

IGMP snooping establishes and maintains a Layer 2 multicast forwarding table to guide multicast data to be forwarded on demand at the data link layer. By configuring IGMP snooping on the switch, multicast data will not be broadcast at Layer 2, but will be sent to the concerned receiver by the switch.

Procedure

Step1 Configure VLAN and VLAN interface.

admin@XorPlus# set vlans vlan-id 2222
admin@XorPlus# set vlans vlan-id 3333
admin@XorPlus# set interface gigabit-ethernet te-1/1/23 family ethernet-switching native-vlan-id 2222
admin@XorPlus# set interface gigabit-ethernet te-1/1/24 family ethernet-switching native-vlan-id 2222
admin@XorPlus# set interface gigabit-ethernet te-1/1/25 family ethernet-switching native-vlan-id 3333
admin@XorPlus# set interface gigabit-ethernet te-1/1/26 family ethernet-switching native-vlan-id 2222
admin@XorPlus# set vlans vlan-id 2222 l3-interface vlan2222
admin@XorPlus# set vlans vlan-id 3333 l3-interface vlan3333
admin@XorPlus# set l3-interface vlan-interface vlan3333 address 172.168.33.1 prefix-length 24
admin@XorPlus# set l3-interface vlan-interface vlan2222 address 192.168.22.1 prefix-length 24

Step2 Enable IP routing.

admin@XorPlus# set ip routing enable true

Step3 Enable PIM on all the VLAN interfaces, configure IGMP on host-side VLAN interface.

admin@XorPlus# set protocols pim interface vlan3333
admin@XorPlus# set protocols pim interface vlan2222
admin@XorPlus# set protocols igmp interface vlan2222 version 3

Step4 Enable IGMP snooping on host VLAN.

admin@XorPlus# set protocols igmp-snooping enable true
admin@XorPlus# set protocols igmp-snooping vlan-id 2222 enable true

Step5 Commit the configurations.

admin@XorPlus# commit

Verify Configuration

Run the command run show igmp groups to show information about multicast groups and member ports.

admin@XorPlus# run show igmp groups
Total IGMP groups: 1
Watermark warn limit(Not Set): 0
Interface        Address         Group           Mode Timer    Srcs V Uptime 
vlan2222         192.168.22.1    224.1.1.1       INCL --:--:--    1 3 00:03:01

Run the command run show mroute to show the PIM routing table information.

admin@XorPlus# run show mroute
IP Multicast Routing Table
Flags: S - Sparse, C - Connected, P - Pruned
       R - SGRpt Pruned, F - Register flag, T - SPT-bit set 

Source             Group          Flags     Proto    Input            Output           TTL  Uptime
172.168.33.100     224.1.1.1      SCFT      PIM      vlan3333         pimreg           1    00:09:45
                                            IGMP     vlan2222                          1

You can use the run show igmp-snooping groups command to show information about the Layer 2 multicast forwarding table.

admin@XorPlus# run show igmp-snooping groups
Total group count: 1
Vlan      Group               Port List          Type
--------  ------------------  -----------------  --------------
2222      224.1.1.1           te-1/1/23          Dynamic

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