To Next Page

To Previous Page

Multicast Listener Discovery (MLD) Snooping

Introduction to MLD Snooping

There are several roles that network devices may play in an IPv6 multicast

environment:

■ MLD host—a network node that uses MLD to “join” (subscribe to) one

or more multicast groups

■ multicast router—a router that routes multicast traffic between sub-

nets

■ querier—a switch or multicast router that identifies MLD hosts by

sending out MLD queries, to which the MLD hosts respond

Curiously enough, a network node that acts as a source of IPv6 multicast

traffic is only an indirect participant in MLD snooping—it just provides

multicast traffic, and MLD doesn’t interact with it. (Note, however, that in an

application like desktop conferencing a network node may act as both a

source and an MLD host; but MLD interacts with that node only in its role as

an MLD host.)

A source node creates multicast traffic by sending packets to a multicast

address. In IPv6, addresses with the first eight bits set (that is, “FF” as the first

two characters of the address) are multicast addresses, and any node that

listens to such an address will receive the traffic sent to that address. Appli-

cation software running on the source and destination systems cooperates to

determine what multicast address to use. (Note that this is a function of the

application software, not of MLD.)

For example, if several employees engage in a desktop conference across the

network, they all need application software on their computers. At the start

of the conference, the software on all the computers determines a multicast

address of, say, FF3E:30:2001:DB8::101 for the conference. Then any traffic

sent to that address can be received by all computers listening on that address.

7-3

HP PROCURVE 2910AL Configuration Guide

Other manuals for HP PROCURVE 2910AL