Cisco Catalyst SD-WAN Routing Configuration Guide, Cisco IOS XE Catalyst SD-WAN Release 17.x

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Cisco Catalyst SD-WAN Routing Configuration Guide, Cisco IOS XE Catalyst SD-WAN Release 17.x

Multicast overlay routing for Cisco IOS XE Catalyst SD-WAN

Updated: March 9, 2026

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This overview explains how the system optimizes distribution trees and uses OMP to manage receiver interest and dynamic join/prune actions.

A Cisco IOS XE Catalyst SD-WAN multicast overlay is a routing protocol that:

  • extends Protocol Independent Multicast Source-Specific Multicast (PIM-SSM) over the Cisco Catalyst SD-WAN overlay using Overlay Management Protocol (OMP),

  • integrates PIM-SM in customer VPNs with OMP in the overlay, leverages Cisco IOS XE MVPN, and uses OMP replicators to optimize the multicast distribution tree across the overlay topology, and

  • supports IGMPv2 and IGMPv3 reports, advertising receiver multicast interest to remote Cisco Catalyst SD-WAN routers using OMP and enabling dynamic join or prune actions for optimized and secure multicast delivery over the overlay network.

The Cisco IOS XE Catalyst SD-WAN multicast overlay implementation extends native multicast by creating a secure optimized multicast tree that runs on top of the overlay network.

Protocol Independent Multicast Sparse-Mode (PIM-SM) is deployed in the customer VPNs, and the OMP replicator is used in overlay multicast to optimize the multicast distribution tree.

The Cisco IOS XE Catalyst SD-WAN router advertises receiver's multicast interest using OMP and participates in join or prune actions with replicators, which use OMP to relay these actions to routers providing overlay connectivity to the PIM-RP or source.

Multicast overlay supported features

Note

From Cisco IOS XE Catalyst SD-WAN Release 17.3.2, TLOC extension with multicast and multicast application-aware route policy features are supported.

  • IPv4 Overlay Multicast (PIM SSM), IPv4 Overlay Multicast (PIM ASM)

  • PIM-RP on IOS XE VPN

  • Replicator with geo-location (GPS)

  • Static RP and Auto-RP

  • PIM Bootstrap Router (BSR)

  • IGMP v2, IGMP v3, and PIM on service side

  • IPSec and GRE Encapsulation

  • vEdge and IOS XE Catalyst SD-WAN Interop

  • Overlay Multicast Signaling using OMP

Multicast overlay supported protocols

Protocol Independent Multicast

Cisco IOS XE Catalyst SD-WAN overlay multicast supports PIM version 2 with some restrictions.

On the service side, the Cisco IOS XE Catalyst SD-WAN software supports native multicast. A router appears as a native PIM router and establishes PIM neighborship with other PIM routers at a local site. A Cisco IOS XE SD-WAN router supports a directly connected local source, referred as a first hop router (FHR).

Receivers residing downstream of a router can join multicast streams by exchanging IGMP membership reports directly with the device, and no other routers are required. Additionally, the Cisco Catalyst SD-WAN router can act as the PIM-RP for the local site.

On the transport side, PIM-enabled Cisco IOS XE Catalyst SD-WAN routers originate multicast service routes (called multicast autodiscover routes), sending them using OMP to the Cisco Catalyst SD-WAN Controllers. The multicast autodiscover routes indicate whether the router is a replicator and the local threshold. Each PIM router also conveys information learned from the PIM join messages sent by local-site multicast-enabled routers, including multicast group state, source information, and RPs. These routes assist Cisco IOS XE Catalyst SD-WAN routers in performing optimized joins across the overlay when joining existing multicast sources.

Cisco IOS XE Catalyst SD-WAN routers support both PIM source-specific mode (SSM) and ASM (Any Source Multicast) mode.

Rendezvous Points

The root of a PIM multicast shared tree resides on a router configured to be a rendezvous point (RP). In the Cisco Catalyst SD-WAN solution, RPs can be Cisco Catalyst SD-WAN routers or non-Cisco Catalyst SD-WAN routers that reside in the local site.

Cisco IOS XE Catalyst SD-WAN supports the following modes of RP discovery:

  • Static RP

  • Auto-RP

  • Auto-RP Proxy

Dynamic RP-group mappings are propagated in the Cisco IOS XE Catalyst SD-WAN solution using Auto-RP. ACLs can be used to control or map certain group ranges to a specific RP. With this information, each PIM router has the ability to forward joins to the correct RP for the group that a downstream IGMP client is attempting to join. Auto-RP updates are propagated to downstream PIM routers if such routers are present in the local site and across the overlay to the remote sites that belong to the same VPN. While using Auto-RP, Replicator Node should be configured as the Auto-RP mapping agent.

Another RP selection model called bootstrap router (BSR) was introduced after Auto-RP in PIM-SM version 2. Auto-RP is a Cisco proprietary protocol, whereas PIM BSR is part of the PIM version 2 specification. BSR performs similarly to Auto-RP in that it uses candidate routers for the RP function and for relaying the RP information for a group.

For sources and receivers in a single site, RP device also must be in the same site.

Replicators

For efficient use of WAN bandwidth, strategic Cisco IOS XE Catalyst SD-WAN routers can be deployed and configured as replicators throughout the overlay network. Replicators mitigate the requirement for a Cisco Catalyst SD-WAN router with local sources or the PIM-RP to replicate a multicast stream once for each receiver. As discussed above, replicators advertise themselves, using OMP multicast-autodiscover routes, to the Cisco Catalyst SD-WAN Controllers in the overlay network. The controllers then forward the replicator location information to the PIM-enabled Cisco IOS XE Catalyst SD-WAN routers that are in the same VPN as the replicator.

A replicator Cisco IOS XE Catalyst SD-WAN router receives streams from multicast sources, replicates them, and forwards them to other Cisco Catalyst SD-WAN routers with multicast receivers in the same VPN. The details of the replication process are discussed below, in the section Multicast Traffic Flow through the Overlay Network. A replicator is typically a Cisco IOS XE Catalyst SD-WAN router located at a colo-site or another site with a higher-speed connection to the WAN transport network.

Multicast Service Routes

Cisco IOS XE Catalyst SD-WAN routers send multicast service routes to the Cisco Catalyst SD-WAN Controller using OMP. From these routes, the controller processes and forwards joins for requested multicast groups towards the source address or PIM-RP as specified in the original PIM join message that resulted in a Cisco Catalyst SD-WAN router advertising the OMP multicast service route. The source address can be either the IP address of an RP if the originating router is attempting to join the PIM shared tree or the IP address of the actual source of the multicast stream if the originating router is attempting to join the source tree.

Internet Group Management Protocol

Cisco IOS XE Catalyst SD-WAN routers support the Internet Group Management Protocol (IGMP) V2 and V3 protocol.

IGMP is used by IPv4 hosts and routers to indicate their interest and in receiving multicast traffic for particular multicast groups. IGMP v3 report is used to indicate interest for a particular multicast group traffic from a specific source.

From these membership reports, Cisco IOS XE Catalyst SD-WAN routers originate the corresponding PIM join or OMP service route advertisements.

MSDP

Summary

Multicast Source Discovery Protocol (MSDP) is a method of connecting multiple PIM-SM domains, and it is used to discover multicast sources in other PIM domains. When MSDP is configured in a network, rendezvous points (RP) exchange source information with RPs in other domains by maintaining MSDP peer relationships with MSDP-enabled routers in other domains. This peering relationship occurs over a TCP connection. A Cisco IOS XE Catalyst SD-WAN device can be configured as a RP so that it discover active sources outside of its domain.

Workflow

Figure 1. MSDP

Here is an illustration of the sequence of events that occur when MSDP is implemented:

  1. When a PIM designated router (DR) in domain A registers a source with its RP in domain A, the RP sends a Source Active (SA) message to all of its RP MSDP peers. The SA message identifies the source address, the group that the source is sending to, and the address or the originator ID of the RP, if configured.

  2. The RP MSDP peer in domain B when it receives the SA message sends the SA message to all of its peers downstream.

  3. The RP MSDP peer in domain B checks if there are any receivers of the advertised groups in its domain. If there are receivers in the group, the RP MSDP peer in domain B sends an (S, G) join toward the source. As a result, a connection is established between domain A and domain B. As multicast packets arrive at the RP, they are then forwarded down to the receivers in the RP’s domain. When the receivers receiving the multicast traffic learns of the source outside the PIM-SM domain (through the arrival of a multicast packet from the source), it can then send a PIM join toward the source and join source’s domain to receive the multicast traffic.

Restrictions for multicast overlay routing

Multicast overlay routing does not support these features:

  • MSDP/Anycast-RP on Cisco Catalyst SD-WAN routers.

  • IPv6 overlay and IPv6 underlay.

  • Dynamic BFD tunnel for multicast.

  • Multicast with asymmetric unicast routing.

  • Multicast overlay working does not support Data Policy. If a data policy is configured, only the required traffic is matched and multicast traffic is not matched.

  • The Cisco vEdge device is used only as the Last Hop Router (LHR), whereas Cisco IOS XE Catalyst SD-WAN devices can be used in all multicast roles (FHR, LHR, RP and Replicator roles).

  • Bidirectional PIM is not supported with hub-and-spoke or full-mesh deployments.

  • On Cisco 1000 Series Integrated Services Routers, when IGMP snooping is enabled and there are no local receivers for multicast traffic in the VLAN, the multicast traffic floods to all ports in the VLAN.

Restrictions for multicast routing with hub-and-spoke topology

Minimum supported releases: Cisco IOS XE Catalyst SD-WAN Release 17.15.1a and Cisco Catalyst SD-WAN Manager Release 20.15.1.

  • You can configure multicast rendezvous point and replicator node on hub-site devices only. Replicator cannot be configured on spoke-site devices.

  • MSDP interconnect feature is not supported with hub-and-spoke multicast deployment.

  • You can configure multicast routing on hub-and-spoke using CLI add-on template only.

  • On-demand tunnel between spoke sites is not supported with multicast.

  • Multicast is supported only with centralized control policy–based hub-and-spoke deployment. Intent-based configuration, as described in the Hub-and-Spoke chapter, is not supported.