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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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Configuring IGMP on a Router

A router by default is not configured to support multicast traffic. There are a few basic configuration tasks that need to be performed on Cisco IOS routers in order to enable multicast on the network.

Step 1. Enable multicast routing on the router in global configuration mode.
```
ip multicast-routing
```
Step 2. Configure PIM routing on the associated interface(s) in the interface configuration mode. Take into consideration that multicast traffic may traverse many different paths and it is always a good idea to enable it on every interface that may need to participate. This might save you some troubleshooting time in the future. When you configure an interface for PIM, it is automatically configured to use IGMPv2 on most current operating systems.
```
ip pim sparse-mode
```
On Cisco switches, IGMP version 2 is enabled by default.
Step 3. If necessary, change the IGMP version supported on an interface.
```
ip igmp version [1,2,3]
```

8. Mixed Groups: Interoperability Between IGMPv1, v2, and v3 | Next Section Previous Section

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