Multicast Routing Enablement in Cisco SD-WAN Overlay

300-415 By islever Editorial Last updated

Describe multicast support in Cisco SD-WAN

Short answer

D The vSmart controller originates multicast service routes to the WAN Edge routers via OMP, which then forwards joins for requested multicast groups based on IGMP v2 or v3 toward the source or PIM-RP as specified in the original PIM join message.

Question

How is multicast routing enabled on devices in the Cisco SD-WAN overlay network?
  1. The WAN Edge routers originate multicast service routes to the vSmart controller via OMP, which then forwards joins for requested multicast groups based on IGMP v2 or v3 toward the source or PIM-RP as specified in the original PIM join message.
  2. The WAN Edge routers originate multicast service routes to the vSmart controller via OMP, which then forwards joins for requested multicast groups based on IGMP v1 or v2 toward the source or PIM-RP as specified in the original PIM join message.
  3. The vSmart controller originates multicast service routes to the WAN Edge routers via OMP, which then forwards joins for requested multicast groups based on IGMP v1 or v2 toward the source or PIM-RP as specified in the original PIM join message.
  4. The vSmart controller originates multicast service routes to the WAN Edge routers via OMP, which then forwards joins for requested multicast groups based on IGMP v2 or v3 toward the source or PIM-RP as specified in the original PIM join message. Correct Answer

Key Takeaways

The key trap is confusing the direction of OMP advertisement (vSmart to Edge, not Edge to vSmart) and outdated IGMP version support (legacy Viptela vs. modern IOS XE).

Learn how multicast is enabled in Cisco SD-WAN: the vSmart controller distributes multicast service routes via OMP to WAN Edge routers, which utilize IGMPv2/v3 for group management.

Common mistake: Candidates often choose A because they mistakenly believe WAN Edges advertise multicast routes to the controller, or B because they recall older Viptela-only IGMPv1/v2 support from early documentation.

Expert Analysis

To determine the correct answer, we must analyze the direction of control plane signaling in Cisco SD-WAN (formerly Viptela) and the supported IGMP versions for modern IOS XE-based WAN Edge routers.

First, consider the direction of multicast route advertisement. In the Cisco SD-WAN architecture, the vSmart controller is responsible for distributing routing information to the WAN Edge routers via the Overlay Management Protocol (OMP). Specifically for multicast, the vSmart controller originates multicast service routes and sends them to the WAN Edge routers. The WAN Edge routers do not originate these service routes to the vSmart; rather, they receive them and use local IGMP/PIM mechanisms to manage group membership on the underlay or customer side. This eliminates options A and B, which incorrectly state that WAN Edge routers originate routes to the vSmart.

Second, examine the supported IGMP versions. While legacy Viptela OS platforms primarily supported IGMPv1 and IGMPv2, modern Cisco IOS XE SD-WAN platforms support both IGMPv2 and IGMPv3. The question asks about "devices in the Cisco SD-WAN overlay network" in a general sense, but current exam standards and documentation for IOS XE emphasize the support for IGMPv2 and IGMPv3 to handle Source-Specific Multicast (SSM) and other advanced features. Option D correctly identifies that the vSmart originates the routes via OMP and that the devices support IGMPv2 or IGMPv3.

Therefore, the vSmart controller originates multicast service routes to the WAN Edge routers via OMP, and the routers process joins based on IGMPv2 or IGMPv3.

Official Reference

https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/routing/ios-xe-17/routing-book-xe/m-multicast-routing.html

This link opens the official vendor documentation in a new tab.

Exam Strategy

When answering SD-WAN control plane questions, always identify the 'originator' of the service route. For most data plane and service routes in SD-WAN, the vSmart acts as the central distributor to the Edges via OMP. Additionally, distinguish between legacy Viptela capabilities and current IOS XE capabilities, as exams increasingly focus on the latter's broader feature set like IGMPv3/SSM.

Frequently Asked Questions

Does the WAN Edge router originate multicast service routes?

No. In Cisco SD-WAN, the vSmart controller originates multicast service routes and distributes them to the WAN Edge routers via OMP.

Which IGMP versions are supported by IOS XE SD-WAN routers?

Modern IOS XE SD-WAN routers support both IGMPv2 and IGMPv3, enabling features like Source-Specific Multicast (SSM).

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Community Votes

A
50%
B
50%

50% of anonymous learners picked answer A. Votes are pick records left by other test-takers — they are not the verified answer.

Discussion 9 contributions

Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.

From public community threads 9

  1. JTPRO 👍 6
    Correct answer is A The question specifies "Cisco SD-Wan devices" which support IGMP V2 and V3. The old Viptela devices only support IGMP V1 and V2. Cisco bought Viptela and kept the name for a short time, but is phasing it out.
  2. Oritopo 👍 4
    Correct answer is A IOS XE supports both IGMNPv2 and IGMPv3 Viptela OS "listen" for both IGMPv1 and IGMPv2 group membership reports, but only "supports" IGMPv2 to send join request https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/routing/vEdge-20-x/routing-book/m-multicast-routing.html
  3. MajorSalieri 👍 3
    No it supports IGMP v2 and v3..so answer is A https://www.cisco.com/c/en/us/td/docs/routers/sdwan/configuration/routing/ios-xe-17/routing-book-xe/m-multicast-routing.html
  4. Speirsington 👍 1
    It's A From the link... The Cisco IOS XE SD-WAN multicast overlay software extends Protocol Independent Multicast Source-Specific Multicast (PIM-SSM) over the Cisco SD-WAN overlay using Overlay Management Protocol (OMP). Protocol Independent Multicast Sparse-Mode (PIM-SM) is deployed in the customer VPNs, and the Cisco IOS XE MVPN is used to integrate PIM in customer VPNs and OMP in the overlay. The OMP replicator is used in overlay multicast to optimize the multicast distribution tree across the overlay topology. The Cisco IOS XE SD-WAN router supports IGMPv2 and IGMPv3 reports and advertises receiver's multicast interest to remote Cisco SD-WAN routers using OMP. Depending on the level of optimization required, the Cisco SD-WAN routers join or prune to or from the replicators, and replicators use OMP to relay the join or prune to the Cisco SD-WAN router providing overlay connectivity to the PIM-RP or source.
  5. eoogengootoo 👍 1
    Cisco SD-WAN overlay multicast routing supports the Internet Group Management Protocol (IGMP) version 2 (defined in RFC 2236 ). Cisco vEdge devices use IGMP to process receiver membership reports for the hosts in a particular VPN and to determine, for a given group, whether multicast traffic should be forwarded and state should be maintained. vEdge routers listen for both IGMPv1 and IGMPv2 group membership reports.
Show 4 more comments
  1. shak5khan786 👍 1 Answered A
    IGMPv2 and IGMPv3 Support: Viptela vEdge and cEdge routers interoperate with IGMPv1/v2/v3 and PIM (Protocol Independent Multicast) on the service side, using OMP (Overlay Management Protocol) to advertise receiver multicast groups across the SD-WAN fabric.
  2. eoogengootoo 👍 1
    Should be B, as Viptela support only IGMP v1 and v2
  3. John662266 👍 1 Answered B
    Option A is IGMP v2 or V3, only B is Correct...
  4. Clouddon 👍 1
    A is the correct answer

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