multicast is not supported on nsx-t environment with TEP Group Feature enabled.
search cancel

multicast is not supported on nsx-t environment with TEP Group Feature enabled.

book

Article ID: 410049

calendar_today

Updated On:

Products

VMware NSX

Issue/Introduction

This article describes a scenario where multicast traffic fails to be forwarded between NSX-T Edge nodes when the "TEP Group" feature is enabled. This results in multicast services within the NSX-T environment not receiving streams, especially when inter-Edge forwarding is required for a specific multicast group.

  • Multicast traffic originating from a VM within NSX-T does not reach its intended receiver if the (S,G) join from the TOR is received on an Edge which is different from Designated Edge (DE) for the multicast group.
  • Logs on the NSX-T T0 Distributed Router (DR) show warning messages similar to IGMP Report for group 239.#.#.# received from unknown label 3####9

    830992:2025-09-09T13:22:10.772Z edge4 NSX 5841 ROUTING [nsx@6876 comp="nsx-edge" subcomp="datapathd" s2comp="igmp-learning" tname="dp-learning3" level="WARN"] IGMP Report for group 239.#.#.# received from unknown label 3####9
    831054:2025-09-09T13:22:42.451Z edge4 NSX 5841 ROUTING [nsx@6876 comp="nsx-edge" subcomp="datapathd" s2comp="igmp-learning" tname="dp-learning3" level="WARN"] IGMP Report for group 239.#.#.# received from unknown label 3####9
    831086:2025-09-09T13:23:11.410Z edge4 NSX 5841 ROUTING [nsx@6876 comp="nsx-edge" subcomp="datapathd" s2comp="igmp-learning" tname="dp-learning3" level="WARN"] IGMP Report for group 239.#.#.# received from unknown label 3####9

  • Multicast Forwarding Information Base (MFIB) entries are not installed on the T0 DR because the VTEP labels received are unrecognised by Multicast since it has received labels related to TEP group feature.
  • Some multicast groups might function correctly if their Designated Edge (DE) is the same as the originating Edge, eliminating the need for inter-Edge multicast forwarding.



Environment

VMware NSX

Cause

The root cause is the enabling of the "TEP Grouping" feature (enable_tep_grouping_on_edge). When this global parameter is set to true, NSX-T Edge nodes include additional, non-standard bits within the VTEP labels. The multicast forwarding path in NSX-T, however, expects a specific VTEP label format. When it encounters these "extra bits" from TEP Grouping, it treats the VTEP label as "unknown" or invalid for multicast operations. This prevents the Multicast Forwarding Information Base (MFIB) from being correctly populated on the T0 Distributed Router (DR), leading to the observed multicast traffic drops during inter-Edge forwarding.

Resolution

The "TEP Grouping" feature (enable_tep_grouping_on_edge) is not compatible with multicast traffic. To resolve this issue, the enable_tep_grouping_on_edge global parameter must be disabled.

Steps:

  1. Validate if TEP Grouping is enabled:
    Use the NSX-T Policy API to retrieve the current connectivity-global-config settings.

    GET /policy/api/v1/infra/connectivity-global-config

    Example output if TEP Grouping is enabled:

    {
  // ...
  "global_replication_mode_enabled": false,
  "is_inherited": false,
  "site_infos": [],
  "tep_group_config": {
    "enable_tep_grouping_on_edge": true <------------- Check this value
  },
  "resource_type": "GlobalConfig",
  "id": "global-config",
  "display_name": "default",
  "path": "/infra/global-config",
  // ...
}

  2. Disable TEP Grouping:
    If enable_tep_grouping_on_edge is true, change its value to false using a PUT call to the NSX-T Policy API.

    PUT /policy/api/v1/infra/connectivity-global-config

    Request Body:

    {
  "global_replication_mode_enabled": false,
  "is_inherited": false,
  "site_infos": [],
  "tep_group_config": {
    "enable_tep_grouping_on_edge": false <------------- Change this to false
  },
  "resource_type": "GlobalConfig",
  "id": "global-config",
  "display_name": "default",
  "path": "/infra/global-config"
}

    Note: the use of multicast is not supported on environment which has enable_tep_grouping_on_edge set to true.

Additional Information

For additional information about TEP Group Feature: https://knowledge.broadcom.com/external/article?articleNumber=324200

Powered by Wolken Software