You can configure multicast on a tier-0 gateway and optionally on a tier-1 gateway for an IPv4 network to send the same multicast data to a group of recipients. 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 will receive packets sent to that group.

The multicast feature has the following capabilities and limitations:
  • PIM Sparse Mode with IGMPv2.
  • No Rendezvous Point (RP) or Bootstrap Router (BSR) functionality on NSX-T Data Center. However, RP information can be learned via PIM Bootstrap Messages (BSMs). In addition, multiple Static RPs can be configured.

    When a Static RP is configured, it serves as the RP for all multicast groups (224/4). If candidate RPs learned from BSMs advertise candidacy for the same group range, the Static RP is preferred. However, if candidate RPs advertise candidacy for a specific group or range of groups, they are preferred as the RP for those groups.

  • The Reverse Path Forwarding (RPF) check for all multicast-specific IPs (senders of data traffic, BSRs, RPs) requires that a route to each of them exists.
  • The RPF check requires a route to each multicast-specific IP with an IP address as the next hop. Reachability via device routes, where the next hop is an interface index, is not supported.
  • Both tier-0 and tier-1 gateways are supported. To enable multicast on a tier-1 gateway, an Edge cluster must be selected and the tier-1 gateway must be linked to a tier-0 gateway that also has multicast enabled.
  • All uplinks on a tier-0 gateway are supported.
  • Multiple Static RPs with discontinuous group ranges are supported.
  • IGMP local groups on uplink interfaces are supported.
  • PIM Hello Interval and Hold Time are supported.
  • (NSX-T Data Center 3.2.0) Active-Cold Standby only is supported. The NSX Edge cluster can be in active-active or active-standby mode. When the cluster is in active-active mode, two of the cluster members will run multicast in active-cold standby mode. You can run the CLI command get mcast high-availability role on each Edge to identify the two nodes participating in multicast. Also note that since unicast reachability to NSX-T Data Center in an active-active cluster is via ECMP, it is imperative that the northbound PIM router selects the ECMP path that matches a PIM neighbor to send PIM Join/Prune messages to NSX-T Data Center. In this way it will select the active Edge node which is running PIM.
  • (NSX-T Data Center 3.2.1 and later) The NSX Edge cluster can be in active-active or active-standby mode. Note that since unicast reachability to NSX-T Data Center in an active-active cluster is via ECMP, it is imperative that the northbound PIM router selects the ECMP path that matches a PIM neighbor to send PIM Join/Prune messages to NSX-T Data Center. In this way it will select the active Edge node which is running PIM.
  • For both active-active and active-standby modes, PIM must be enabled on at least one of the tier-0 uplinks for multicast to work.
  • East-west multicast replication: up to 4 VTEP segments for maximum replication efficiency.
  • ESXi host and NSX Edge only (KVM not supported).
  • Layer 2 bridge attached to a downlink segment not supported.
  • Gateway Firewall services are not supported for multicast. Distributed Firewall and Bridge Firewall are supported.
  • Multi-site (NSX Federation) not supported.
  • Multi-VRF not supported.

Multicast Configuration Prerequisites

Underlay network configurations:
  • Acquire a multicast address range from your network administrator. This will be used to configure the Multicast Replication Range when you configure multicast on a tier-0 gateway (see Configure Multicast).
  • Enable IGMP snooping on the layer 2 switches to which GENEVE participating transport nodes are attached. If IGMP snooping is enabled on layer 2, IGMP querier must be enabled on the router or layer 3 switch with connectivity to multicast enabled networks.

Multicast Configuration Steps

  1. Create an IGMP profile. See Create an IGMP Profile.
  2. Optionally create a PIM profile to configure a Static Rendezvous Point (RP). See Create a PIM Profile.
  3. Configure a tier-0 gateway to support multicast. See Add a Tier-0 Gateway and Configure Multicast.
  4. Optionally configure tier-1 gateways to support multicast. See Add a Tier-1 Gateway.