3com WX3000 Manuel D’Utilisation

 

2-13 

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Before configuring a simulated host, enable IGMP Snooping in VLAN view first.  

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The port to be configured must belong to the specified VLAN; otherwise the configuration does not 

take effect. 

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You can use the source-ip source-address command to specify a multicast source address that 

the port will join as a simulated host. This configuration takes effect when IMGPv3 Snooping is 

enabled in the VLAN.  

 

By configuring the VLAN tag carried in IGMP general and group-specific queries forwarded and sent by 

IGMP Snooping devices and by configuring the VLAN mapping function, you can enable multicast 

packet forwarding between different VLANs In a Layer-2 multicast network environment. 

For description about VLAN mapping, see “QoS-QoS Profile”. 

Follow these steps to configure VLAN Tag for query message: 

Enter system view 

system-view 

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Enable IGMP Snooping 

igmp-snooping enable 

Required 

By default, IGMP Snooping is disabled. 

Configure a VLAN tag 
for query messages 

igmp-snooping 
vlan-mapping vlan 
vlan-id 

Required 

By default, no VLAN tag is configured for 
general and group-specific query messages 
sent or forwarded by IGMP Snooping. 

 

In traditional multicast implementations, when users in different VLANs listen to the same multicast 

group, the multicast data is copied on the multicast router for each VLAN that contains receivers. This is 

a big waste of network bandwidth. 

In an IGMP Snooping environment, by configuring a multicast VLAN and adding ports to the multicast 

VLAN, you can allow users in different VLANs to share the same multicast VLAN. This saves bandwidth 

because multicast streams are transmitted only within the multicast VLAN. In addition, because the 

multicast VLAN is isolated from user VLANs, this method also enhances the information security. 

Multicast VLAN is mainly used in Layer 2 switching, but you must make the corresponding 

configurations on the Layer 3 device. 

Follow these steps to configure multicast VLAN on the Layer 3 device: 

Enter system view 

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Create a multicast VLAN and 
enter VLAN view 

vlan vlan-id 

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Return to system view 

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