This guide applies to the following firmware versions:

Omada Software Controller Version 5.9 and above

OC200(UN)_V1_1.24.0 Build 20230328 and above

OC200(UN)_V2_2.9.3 Build 20230328 and above

OC300(UN)_V1_1.17.0 Build 20230328 and above

OC400(UN)

SX6632YF/SG6654X/SG6654XHP/SG6428X/SG6428XHP

This article focuses on configuring the PIM-DM function on the Omada L3 switches. Since the Omada controllers don’t support configuring PIM-related functions on switches through the GUI, you need to use the CLI commands to perform the configurations in the controller mode. In the standalone mode, PIM-related functions can be configured directly through the management page.

PIM-DM Application Scenarios

The Protocol Independent Multicast (PIM) provides routing for IP multicast using unicast static routing or unicast routing tables generated by any unicast routing protocol. Independent of the unicast routing protocol used, multicast routing generates corresponding multicast routing table entries through the unicast routing protocol.

PIM-DM, a dense-mode multicast routing protocol that uses the Push mode to transmit multicast data, is suitable for small networks with dense multicast group members. PIM-DM assumes that all branches in the network have multicast receivers, so it first spreads the multicast data to the entire network and then prunes the branches without receivers, leaving only the ones with receivers. When a receiver is generated on the pruned branch, the grafting mechanism will be used to restore the branch.

A typical scenario for PIM-DM application:

The Source sends 16 channels of multicast data streams (235.0.0.51~235.0.0.66). Now Host A wants to join the group 235.0.0.51, and Host C wants to join the group 235.0.0.52.

Device	Interface	IP Address	VLAN
Switch A	GE 1/0/1	10.110.1.1/24	100
Switch A	GE 1/0/2	192.168.11.1/24	101
Switch B	GE 1/0/1	10.110.2.1/24	200
Switch B	GE 1/0/2	192.168.12.1/24	102
Switch C	GE 1/0/1	10.110.2.2/24	200
Switch C	GE 1/0/2	192.168.13.1/24	103
Switch D	GE 1/0/1	10.110.5.1/24	300
	GE 1/0/2	192.168.11.2/24	101
	GE 1/0/3	192.168.12.2/24	102
	GE 1/0/4	192.168.13.2/24	103

Video-on-demand streams are sent to receiver hosts in multicast. Receiver groups from different organizations form the stub networks, each with at least one receiver. The entire PIM domain uses the DM mode.

Host A and Host C are multicast receivers on two stub networks; Switch D is connected to the network where the multicast source (Source) is located through GE 1/0/1; Switch A is connected to the stub network N1 through GE 1/0/1 and to Switch D through the GE 1/0/2; Switch B and Switch C are connected to the stub network N2 through their respective GE 1/0/1 interfaces and are connected to Switch D through their respective GE 1/0/2 interfaces.

IGMP runs between Switch A and stub network N1; it also runs between Switch B/C and stub network N2.

For such a case, configure PIM-DM in the following three steps:

1. Configure unicast routing protocols (such as RIP/OSPF) on the switches supporting PIM-DM within the domain to ensure that routes to each subnet are reachable.

2. Configure the switch on the stub network in the PIM domain: enable IP multicast routing, PIM-DM, and IGMP on the corresponding interfaces.

3. Enable IP multicast routing and PIM-DM on all interfaces on the switch on the multicast source in the PIM domain.

PIM-DM Configuration Guide

Below is an example to demonstrate the configuration of PIM-DM. Before proceeding with the following configurations, configure each interface's IP address and subnet mask and ensure that the routing is reachable between devices within the PIM-DM domain.

1. Configure the unicast routing protocol within the domain to ensure the reachability of each subnet. For more information, please refer to the RIP/OSPF configuration guide.

2. Configure the switch on the stub network within the PIM domain.

Through this step, the switch on the stub network will be able to obtain the multicast group member information through IGMP and manage multicast routing through PIM.

2.1. In standalone mode (taking Switch A as an example):

Go to L3 features > Multicast Routing > Global Config to enable Multicast Routing, select PIM DM for Protocol Mode, and then click Apply.

Next, go to the PIM DM configuration page and proceed with the PIM DM interface config.

Select the interfaces where you want to enable PIM DM (VLAN101 on switch A, VLAN102 on switch B, and VLAN103 on switch C).

Change the interface status to Enable, configure other parameters according to your requirements (the default Hello Interval is 30 seconds), and then click Apply.

When configuring PIM DM, you must enable the IGMP feature on the interfaces connecting to the host. Taking switch A as an example:

Go to L3 Features > IGMP > Global Config, then enable Admin Mode.

Next, go to Interface Config and enable IGMP on VLAN100, the interface connecting to the host. You can configure the version and other parameters based on your needs. The default parameters are as follows:

2.2 Configuring PIM-DM on the switch on the stub network in controller mode

To proceed with the configurations, follow these steps:

Go to Setting > CLI configuration > Device CLI > Create New Device CLI profile, then send the following commands separately to Switch A, Switch B, and Switch C:

Switch A:

ip multicast-routing

ip igmp

ip pim dense-mode

interface vlan 101

ip pim

interface vlan 100

ip pim

ip igmp

Switch B:

ip multicast-routing

ip igmp

ip pim dense-mode

interface vlan 102

ip pim

interface vlan 200

ip pim

ip igmp

Switch C:

ip multicast-routing

ip igmp

ip pim dense-mode

interface vlan 103

ip pim

interface vlan 200

ip pim

ip igmp

Note: IGMP Querier Election: The switch with the smaller IP address will become the IGMP querier. An Assert Winner election will occur when multiple PIM upstream routers exist within a subnet. If the route priority and cost are the same, the switch with the larger IP address will be elected as the Assert Winner. The Assert Winner will forward the multicast data stream downstream to clients.

In the sample topology, there is an IGMP Querier and PIM Assert Winner election between Switch B and Switch C. According to the configuration in the sample topology, Switch B becomes the IGMP Querier, and Switch C becomes the Assert Winner that forwards the multicast stream to the group members in Network 2.

3. Configuring the switch at the multicast source within the PIM domain

After configuring the switches connected to the stub networks, you must enable PIM on other switches within the PIM domain (only Switch D in the sample topology). Here we take Switch D as an example to demonstrate the configuration:

3.1 In Standalone mode:

Go to L3 features > Multicast Routing > Global Config to enable Multicast Routing, select PIM DM for Protocol Mode, then click Apply.

Next, go to the PIM DM configuration page and proceed with the PIM DM interface configuration.

Select the interfaces where you want to enable PIM DM. For Switch D, enable PIM on all non-default interfaces: Change the interface status to Enable and configure other parameters based on the scenario requirements. You can refer to the default parameters mentioned in the previous section. Then click Apply.