Routing Protocols Configuration Guide

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How traffic flows in multicast overlay routing

Updated: February 6, 2026

Overview

This section illustrates the interaction between edge devices and replicators to provide a clear picture of data plane operations and the sequence of events during distribution.

Summary

The following illustration represents the example topology for multicast overlay routing on Cisco IOS XE Catalyst SD-WAN devices:

Workflow

Figure 1. Multicast Overlay Routing Topology

How multicast overlay protocols work in a hub-and-spoke topology

Use cases for multicast routing on hub-and-spoke

From Cisco IOS XE Catalyst SD-WAN Release 17.15.1a and Cisco Catalyst SD-WAN Manager Release 20.15.1, a source can send a single packet of data to a single multicast address using multicast overlay protocols in a hub-and-spoke topology. This single packet is then distributed to an entire group of recipients.

  • A sender in a hub site sending multicast traffic to receivers in same or other hub sites.

  • A sender in a hub site sending multicast traffic to receivers in spoke sites.

  • A sender in a spoke site sending multicast traffic to receivers in hub sites.

  • A sender in a spoke site sending multicast traffic to receivers in same/other spoke sites.

Summary

The illustration has the following configurations:

Workflow

Figure 1. Multicast Configuration

  • Any Source Multicast (ASM) with static or AutoRP

  • No BFD session between hub sites across different regions

  • No BFD sessions between spoke sites

  • BFD session must be present between hub sites and all the spoke sites across all regions

  • For every site (both hub and spoke) define a control policy. The site-list of the policy specifies all hub and spoke sites excluding the site on which the policy is applied.

  • There should be at least one unicast subnet with NextHop as Cisco IOS XE Catalyst SD-WAN device in the route table to forward multicast traffic. This is applicable to Hub-Spoke, Full Mesh and Dual Border scenarios too.

  • Configuration Example of Hub-and-spoke Multicast Using the CLI

Configuration example of hub-and-spoke multicast using the CLI

The following example shows the configuration of centralized control policy for hub-and-spoke deployment:

policy
 lists
  tloc-list Hub-TLOCs
   tloc 10.10.10.2 color biz-internet encap ipsec
   tloc 192.0.2.1 color biz-internet encap ipsec
  !
  site-list Branches
   site-id 140
   site-id 68
  !
  site-list DCs
   site-id 50
   site-id 67
  !
 !
 control-policy Hub-Control-Policy
  sequence 11
   match tloc
    site-list DCs
   !
   action accept
   !
  !
  sequence 31
   match route
    site-list DCs
   !
   action accept
   !
  !
  default-action reject
 !
 control-policy Spoke-Control-Policy
  sequence 1
   match tloc
    site-list Branches
   !
   action reject
   !
  !
  sequence 11
   match tloc
    site-list DCs
   !
   action accept
   !
  !
  default-action reject
 !
!
apply-policy
 site-list Branches
  control-policy Spoke-Control-Policy out
 !
 site-list DCs
  control-policy Hub-Control-Policy out
 !
!

The following example shows the spoke configuration for hub-and-spoke multicast deployment:

sdwan
 multicast        
  address-family ipv4 vrf 1
   spoke
  !
 !
!