DES-3326S Layer 3 Fast Ethernet Switch User’s Guide

the router should forward multicast packets it receives to the subnetworks it is attached to or not. A multicast router that has received a multicast packet will check to determine if there is at least one member of a multicast group that has requested to receive multicast packets from this source. If there is one member, the packet is forwarded. If there are no members, the packet is dropped.

IGMP Versions 1 and 2

Users that want to receive multicast packets need to be able to join and leave multicast groups. This is accomplished using IGMP.

 

 

 

Figure 5-15. IGMP Message Format

 

 

 

The IGMP Type codes are shown below:

 

 

 

Type

 

Meaning

 

 

 

 

 

 

 

0x11

 

Membership Query (if Group Address is 0.0.0.0)

 

 

 

0x1

 

Specific Group Membership Query (if Group Address

1

 

is Present)

 

 

 

0x1

 

Membership Report (version 2)

 

 

6

 

 

 

 

 

0x1

 

Leave a Group (version 2)

 

 

7

 

 

 

 

 

0x1

 

Membership Report (version 1)

 

 

 

 

 

 

 

 

 

Switch Management and Operating Concepts

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D-Link DES-3326S manual Igmp Versions 1, 113