IP multicast routing enables a host (source) to send a single copy of data to a single multicast address. Data is then distributed to a group of recipients by using a special form of IP address called the IP multicast group address. In a multicast environment, any host, regardless of whether it is a member of a group, can send to a group. However, only the members of a group can receive packets sent to that group.

NSX uses two multicast routing protocols: Internet Group Management Protocol (IGMPv2) and Protocol Independent Multicast (PIM). PIM sparse mode is supported (PIM-SM). PIM is used on ESGs, but not on the DLR.

For more information about multicast support in NSX, see Multicast Routing Support, Limitations, and Topology.
Attention: During vMotion of virtual machines that are receivers of multicast, a 1–2 second multicast traffic loss can occur.

Prerequisites

Transport Zones must have a multicast address range configured. See Assign a Segment ID Pool and Multicast Address Range in the NSX Installation Guide.

IGMP configuration must be the same across the Edge Services Gateway and the Logical (Distributed) Router.

Enable IGMP snooping on the L2 switches to which VXLAN participating hosts are attached. If IGMP snooping is enabled on L2, IGMP querier must be enabled on the router or L3 switch with connectivity to multicast enabled networks. See Add a Logical Switch.

Procedure

  1. In the vSphere Client, navigate to Networking & Security > NSX Edges.
  2. Click a logical (distributed) router.
  3. Click Routing > Multicast.
  4. Enable multicast.
    Version Procedure
    NSX 6.4.2 to 6.4.4

    In Configuration, click the toggle switch to enable multicast.

    NSX 6.4.5 and later
    1. Next to Configuration, click Edit.
    2. In Status, click the toggle switch to enable multicast.
  5. Enter the replication multicast range.
    Version Procedure
    NSX 6.4.2 to 6.4.4

    In Replication Multicast Range, enter a range of multicast group addresses in the CIDR format.

    NSX 6.4.5 and later
    1. Next to Configuration, click Edit.
    2. In Replication Multicast Range, enter a range of multicast group addresses in the CIDR format.
    Replication Multicast Range is a range of multicast group addresses (VXLAN outer destination IP) that is used to replicate workload/tenant multicast group addresses (VXLAN inner destination IP). Replication Multicast Range IP addresses should not overlap with the multicast address range, configured in Networking & Security > Installation and Upgrade > Logical Network Settings. For more information, see Assign a Segment ID Pool and Multicast Address Range in the NSX Installation Guide.
  6. Configure IGMP parameters. IGMP messages are used primarily by multicast hosts to signal their interest in joining a specific multicast group, and to begin receiving group traffic. IGMP Parameters configured on the DLR must match those configured on the ESG, and have to be configured globally for the ESG and the DLR.
    IGMP Parameter Description
    Query Optional. Configures the frequency at which the designated router sends IGMP host-query messages. The default is 30 seconds. Maximum value is 3,744 seconds.
    Query Max Response Time (sec) Optional. Sets the maximum amount of time that can elapse between when the querier router sends a host-query message and when it receives a response from a host. The default is 10 seconds. Maximum value is 25 seconds.
    Last Member Query Interval (sec)

    Optional. Configures the interval at which the router sends IGMP group-specific query messages. The default is 1 second. Maximum value is 25 seconds.

    Robustness Variable Optional. The default value is 2. Maximum value is 255.
  7. Under Enabled Interfaces, click Configure Interfaces and enable multicast on the uplink and internal interfaces.
    Note:
    • Multicast must be enabled on all the DLRs that should receive IPv4 multicast packets.
    • On a DLR, multicast is supported on a single uplink interface and on multiple internal interfaces.
  8. Click Publish for the changes to take effect.

Results

To verify the multicast routing configurations on a given host and DLR, run the CLI command: show logical-router host <host ID> dlr <DLR instance> mrouting-domain

In the example output below, the host is host-19 and the DLR instance is edge-1: 

cli>show logical-router host host-19 dlr edge-1 mrouting-domain
VDR Mcast Routing Domain configurations:
Vdr Name: edge-1
Vdr ID: 0x00002328
Multicast Routing Doman: Enabled
Replication Mcst Grp Start IP: 237.0.0.0
Replciation Mcast Grp Mask: 255.255.255.0
Control VNI: 9008
Uplink VNI: 9007
IGMP Query Interval: 30 sec
IGMP Query Response Interval: 10 sec
IGMP Robustness Variable: 2
Group membership Interval: 70 se