Multimedia Traffic Control with IP Multicast (IGMP)

How IGMP Operates

Operation With or Without IP Addressing

You can configure IGMP on VLANs that do not have IP addressing. The benefit of IGMP without IP addressing is a reduction in the number of IP addresses you have to use and configure. This can be significant in a network with a large number of VLANs. The limitation on IGMP without IP addressing is that the switch cannot become Querier on any VLANs for which it has no IP address— so the network administrator must ensure that another IGMP device will act as Querier. It is also advisable to have an additional IGMP device available as a backup Querier. See the following table.

Table 4-1.Comparison of IGMP Operation With and Without IP Addressing

IGMP Function Available With IP Addressing

Available

Operating Differences

Configured on the VLAN

Without IP

Without an IP Address

 

Addressing?

 

 

 

 

Forward multicast group traffic to any port on

Yes

None

the VLAN that has received a join request for

 

 

that multicast group.

 

 

 

 

 

Forward join requests (reports) to the Querier.

Yes

None

 

 

 

Configure individual ports in the VLAN to Auto

Yes

None

(the default)/Blocked, or Forward.

 

 

 

 

 

Configure IGMP traffic forwarding to normal or

Yes

None

high-priority forwarding.

 

 

 

 

 

 

 

 

Age-Out IGMP group addresses when the last

Yes

Requires that another IGMP device in the VLAN has an IP

IGMP client on a port in the VLAN leaves the

 

address and can operate as Querier. This can be a

group.

 

multicast router or another switch configured for IGMP

 

 

operation. (ProCurve recommends that the VLAN also

Support Fast-Leave IGMP (below) and Forced

Yes

include a device operating as a backup Querier in case

Fast-Leave IGMP (page 4-15).

 

the device operating as the primary Querier fails for any

 

 

reason.

 

 

 

Support automatic Querier election.

No

Querier operation not available.

 

 

 

Operate as the Querier.

No

Querier operation not available.

 

 

 

Available as a backup Querier.

No

Querier operation not available.

 

 

 

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