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C
HAPTER
8: M
ULTICAST
F
ILTERING
What is a
Multicast?
A multicast is a packet that is sent to a subset of endstations in a LAN, or
VLAN, that belong to a
multicast group
. If the network is set up correctly,
a multicast can only be sent to an endstation if it has joined the relevant
group.
A typical use of multicasts is video-conferencing, where high volumes of
traffic need to be sent to several endstations simultaneously, but where
broadcasting that traffic to all endstations would seriously reduce
network performance.
What is Multicast
Filtering?
Multicasts are similar to broadcasts — by default, they are sent to all
endstations on a LAN or VLAN. Multicast filtering is the system by which
endstations only receive multicast traffic if they register to join specific
multicast groups. With multicast filtering, network devices only forward
multicast traffic to the ports that are connected to registered endstations.
Figure 44
The effect of multicast filtering
Summary of Contents for SuperStack II
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Page 154: ...154 CHAPTER 4 WORKING WITH THE COMMAND LINE INTERFACE ...
Page 156: ......
Page 162: ...162 CHAPTER 5 PORT TRUNKS ...
Page 169: ...VLANs and Your Switch 169 Figure 32 Forwarding unknown 802 1Q tags ...
Page 173: ...VLAN Configuration for Beginners 173 Figure 34 Simple example Untagged connections using hubs ...
Page 180: ...180 CHAPTER 6 VIRTUAL LANS VLANS ...
Page 188: ...188 CHAPTER 7 FASTIP ...
Page 200: ...200 CHAPTER 9 SPANNING TREE PROTOCOL Figure 49 STP configurations ...
Page 210: ...210 CHAPTER 10 RMON ...
Page 211: ...IV PROBLEM SOLVING Chapter 11 Problem Solving ...
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Page 224: ...224 CHAPTER 11 PROBLEM SOLVING ...
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