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Network Access and Layer 2 Multicast

Sample Chapter is provided courtesy of Cisco Press.
Date: Nov 19, 2016.

Chapter Information

Layered Encapsulation
MAC Address Mapping
Switching Multicast Frames
Group Subscription
IGMP on the Gateway Router
IGMP Versions
Configuring IGMP on a Router
Mixed Groups: Interoperability Between IGMPv1, v2, and v3
Layer 2 Group Management
Snooping
The Process of Packet Replication in a Switch
Protecting Layer 2
Summary
References

Chapter Description

In this chapter from IP Multicast, Volume I: Cisco IP Multicast Networking, authors Josh Loveless, Ray Blair, and Arvind Durai take an in-depth look at IP multicast messages at Layer 2 and how they are transported in a Layer 2 domain. This chapter covers the basic elements of multicast functionality in Layer 2 domains as well as design considerations for multicast deployments.

From the Book

IP Multicast, Volume I: Cisco IP Multicast Networking

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Mixed Groups: Interoperability Between IGMPv1, v2, and v3

It all boils down to the least common denominator. When there is a mix of hosts on a subnet, the only method for them to communicate is with the lowest IGMP version number used by a host. This is due to the fact that higher versions understand lower versions for backward compatibility.

The other situation you may encounter is having a mix of clients and several routers on a subnet. There is no mechanism for routers configured with a lower IGMP version to detect a router running a higher version IGMP. This requires manual intervention, and someone must configure the routers to use the same version.

9. Layer 2 Group Management | Next Section Previous Section

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