3com 5500-ei pwr Installation Instruction

 

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To prevent bursting traffic in the network or performance deterioration of the device caused by 

excessive multicast groups, you can set the maximum number of multicast groups that the switch 

should process.  

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When the number of multicast groups exceeds the configured limit, the switch removes its 

multicast forwarding entries starting from the oldest one. In this case, the multicast packets for the 

removed multicast group(s) will be flooded in the VLAN as unknown multicast packets. As a result, 

non-member ports can receive multicast packets within a period of time. To avoid this from 

happening, enable the function of dropping unknown multicast packets.  

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If an Ethernet port is a static member port for a multicast group, the configuration of the maximum 

number of multicast groups that can be joined does not take effect on the port.  

 

In an IP multicast network running IGMP, one dedicated multicast device is responsible for sending 

IGMP general queries, and this router or Layer 3 switch is called the IGMP querier.  

However, a Layer 2 multicast switch does not support IGMP, and therefore cannot send general queries 

by default. By enabling IGMP Snooping querier on a Layer 2 switch in a VLAN where multicast traffic 

needs to be Layer-2 switched only and no multicast routers are present, the Layer 2 switch will act as a 

querier to send IGMP general queries, thus allowing multicast forwarding entries to be established and 

maintained at the data link layer.  

Upon receiving an IGMP query with the source IP address 0.0.0.0 on a port, the switch does not enlist 

that port as a dynamic router port. This may prevent multicast forwarding entries from being correctly 

created at the data link layer and cause multicast traffic forwarding failure in the end. When a Layer 2 

device acts as an IGMP-Snooping querier, to avoid the aforesaid problem, configure a non-all-zero IP 

address as the source IP address of IGMP queries.  

IGMP Snooping querier related configurations include: 

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Enabling IGMP Snooping querier, 

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Configuring the IGMP query interval, and  

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Configuring the source address to be carried in IGMP general and group specific queries.  

Follow these steps to enable IGMP Snooping querier: 

Enter system view 

— 

Enable IGMP Snooping 

Required 

By default, IGMP Snooping is 
disabled. 

Enter VLAN view 

vlan vlan-id 

— 

Enable IGMP Snooping 

Required 

By default, IGMP Snooping is 
disabled.