Step 4:

NOTE

Click “Apply” button and save it if everything is OK.

The screen is divided into two sections. Current Spanning Tree Root section displays the read-only Spanning Tree settings for the current root switch and the parameters this switch is to use when it becomes the root switch.

3.8 IGMP

Internet Group Management Protocol (IGMP) is an Internet protocol that provides a way for an Internet computer to report its multicast group membership to adjacent routers. It allows the management switch to forward multicast traffic intelligently. The switch "snoops" the IGMP query and report messages and forwards traffic to only the ports that request the multicast traffic. This prevents

 

the switch from broadcasting the traffic to all ports and

Host Group Addresses

possibly affecting network performance.

Host groups are identified by class D IP

The membership of a host group is dynamic - hosts may join

addresses, i.e., those with "1110" as their

and leave groups at any time. There is no restriction on the

high-order four bits. Class D IP addresses,

i.e., those with "1111" as their high-order

location or number of members in a host group. A host may

four bits, are reserved for future addressing

be a member of more than one group at a time. A host need

modes.

not be a member of a group to send datagrams to it.

In Internet standard "dotted decimal" notation, host group addresses range from

224.0.0.0to 239.255.255.255. The address

224.0.0.0is guaranteed not to be assigned to any group, and 224.0.0.1 is assigned to the permanent group of all IP hosts (including gateways). This is used to address all multicast hosts on the directly connected network. There is no multicast address (or any other IP address) for all hosts on the total Internet. The addresses of other well-known, permanent groups are to be published in "Assigned Numbers".

Figure 3-7 The IGMP Screen page

3.8.1 IGMP Management

To activate IGMP function,

Step 1: Select “enabled” in the IGMP state field.

Step 2: Click on the radio button to select the version for IGMP.

Step 3: Hit on the “Apply” button and save your setting.

3.8.2 Definition on IGMP v1.0 and v2.0

For IGMP v1.0,

The Internet Group Management Protocol (IGMP v1.0) is used by IP hosts to report their host group memberships to any immediately neighboring multicast routers. IGMP is an asymmetric protocol and is specified here from the point of view of a host, rather than a multicast router.

 

IGMPv1 has no leave mechanism. If a host no longer wants to receive the traffic, it simply

NOTE

quits. If it is the last, the router will not have any answers to its query and will delete the GDA

for that subnet.

For IGMP v2.0,

IGMP v2.0 allows group membership termination to be quickly reported to the routing protocol, which is important for high-bandwidth multicast groups and/or subnets with highly volatile group membership.

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