Got it

Multicast traffic is broadcasted on the S5700LI switch even though IGMP snooping is enabled

Latest reply: Apr 24, 2017 01:19:31 1601 1 0 0 0

Hello everyone,

As shown in Figure 1 on a pure Layer 2 network, a multicast source (Host B) sends multicast data to multicast group in VLAN 10. Host C expects to receive data of the multicast group while HostA is not interested in this traffic. All the hosts run IGMPv2.

Figure 1 Networking diagram for IGMP snooping querier configuration 


The switch is configured with IGMP snooping and as the IGMP snooping querier of the L2 network. With this configuration, the switch would periodically broadcast IGMP Query messages to all the interfaces in the VLAN and would be able to establish an L2 multicast forwarding table so that the traffic sent by the multicast sources will be delivered just to the clients that are joining specific groups. In this specific scenario, the switch should send the multicast traffic just to Host C.

After the switch is configured as an IGMP snooping querier we can notice that it continues to flood the multicast stream out on every port in VLAN 10 and does not send it just on the interface where Host C is situated.



vlan batch 10


igmp-snooping enable

vlan 10

igmp-snooping enable

 igmp-snooping querier enable


interface Vlanif10

 ip address


interface GigabitEthernet0/0/1

 description HostA

 port link-type access

 port default vlan 10


interface GigabitEthernet0/0/2

 description Host B- Multicast Source

 port link-type access

 port default vlan 10


interface GigabitEthernet0/0/3

 description Host C-Receiver

 port link-type access

 port default vlan 10

Please help me! Thank you!

  • x
  • convention:

Created Apr 24, 2017 01:19:31

This behavior appears on the S2750, S5700S-LI, S5700LI, S5710-X-LI, S5720S-SI  and S5720SI switches even though igmp snooping is enabled because by default they broadcast unknown multicast flows in the corresponding VLAN, regardless of which Layer 2 multicast forwarding mode is used.

<?xml:namespace prefix = "o" />


In order to correct the IGMP snooping behavior on these devices, you would need to configure the switch to drop unknown multicast flows by running  the multicast drop-unknown command in the vlan view:


[Huawei]vlan 10


[Huawei-vlan10]multicast drop-unknown


After the multicast drop-unknown command is configured, the switch drops all unknown multicast packets, including the protocol packets that are transparently transmitted within the VLAN and use the reserved multicast address.

View more
  • x
  • convention:


You need to log in to comment to the post Login | Register

Notice: To protect the legitimate rights and interests of you, the community, and third parties, do not release content that may bring legal risks to all parties, including but are not limited to the following:
  • Politically sensitive content
  • Content concerning pornography, gambling, and drug abuse
  • Content that may disclose or infringe upon others ' commercial secrets, intellectual properties, including trade marks, copyrights, and patents, and personal privacy
Do not share your account and password with others. All operations performed using your account will be regarded as your own actions and all consequences arising therefrom will be borne by you. For details, see " User Agreement."

My Followers

Login and enjoy all the member benefits


Are you sure to block this user?
Users on your blacklist cannot comment on your post,cannot mention you, cannot send you private messages.
Please bind your phone number to obtain invitation bonus.