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Configuration Guide - IP Multicast

CloudEngine 12800 and 12800E V200R005C10

This document describes the configurations of IP multicast, including IP multicast basics, IGMP, MLD, PIM (IPv4), PIM (IPv6), MSDP, multicast VPN, multicast route management (IPv4), multicast route management (IPv6), IGMP snooping, MLD snooping, static multicast MAC address, multicast VLAN, multicast network management.
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Dropping Unknown Multicast Flows

Dropping Unknown Multicast Flows


Unknown multicast packets are multicast packets that do not match entries in the multicast forwarding table. By default, the switch broadcasts unknown multicast packets in the corresponding VLAN to reduce instant bandwidth usage.


  1. Run system-view

    The system view is displayed.

  2. Run vlan vlan-id

    The VLAN view is displayed.

  3. Run multicast drop-unknown

    The switch is configured to discard unknown multicast packets.

    By default, a switch broadcasts unknown multicast packets in a VLAN.


    If a VLANIF interface on a CE12800 has Layer 3 multicast enabled and is the inbound interface of multicast flows, do not use the multicast drop-unknown command in the corresponding VLAN. Otherwise, multicast flows may fail to be forwarded.

    After the multicast drop-unknown command is configured:
    • A CE12800 switch drops received unknown multicast data flows. As a result, multicast flows may not be forwarded.
    • The CE12800E drops the original unknown multicast data packets. Multicast data flows can be forwarded after the matching multicast forwarding entries are generated.
    • A switch drops IPv6 protocol packets with reserved group addresses, such as Protocol Independent Multicast (PIM) Hello packets, Open Shortest Path First (OSPF) packets, and Bidirectional Forwarding Detection (BFD) packets. If no multicast function is enabled, the switch drops MLD packets. If multicast functions are enabled, the switch processes MLD packets normally.

  4. Run commit

    The configuration is committed.

Updated: 2019-04-20

Document ID: EDOC1100074724

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