Multicast - ZyXEL Communications GS3700 Series User Manual

This chapt er shows you how t o configure various m ult icast feat ures.
23.1 Multicast Overview
Tradit ionally, I P packet s are t ransm it t ed in one of eit her t wo ways - Unicast ( 1 sender t o 1 recipient )
or Broadcast ( 1 sender t o everybody on t he net work) . Mult icast delivers I P packet s t o j ust a group
of host s on t he net work.
I GMP ( I nt ernet Group Managem ent Prot ocol) is a net work- layer prot ocol used t o est ablish
m em bership in an I Pv4 m ult icast group - it is not used t o carry user dat a. Refer t o RFC 1112, RFC
2236 and RFC 3376 for inform at ion on I GMP versions 1, 2 and 3 respect ively.
The Mult icast List ener Discovery ( MLD) prot ocol ( defined in RFC 2710) is derived from I Pv4's
I nt ernet Group Managem ent Prot ocol version 2 ( I GMPv2) . MLD uses I CMPv6 m essage t ypes, rat her
t han I GMP m essage t ypes. MLDv1 is sim ilar t o I GMPv2 and MLDv2 is sim ilar t o I GMPv3. MLD allows
an I Pv6 swit ch or rout er t o discover t he presence of MLD list eners who wish t o receive m ult icast
packet s and t he I P addresses of m ult icast groups t he host s want t o j oin on it s net work.
MLD snooping and MLD proxy are analogous t o I GMP snooping and I GMP proxy in I Pv4. MLD
filt ering cont rols which m ult icast groups a port can j oin.
23.1.1 IP Multicast Addresses
I n I Pv4, a m ult icast address allows a device t o send packet s t o a specific group of host s ( m ult icast
group) in a different subnet work. A m ult icast I P address represent s a t raffic receiving group, not
individual receiving devices. I P addresses in t he Class D range ( 224.0.0.0 t o 239.255.255.255) are
used for I P m ult icast ing. Cert ain I P m ult icast num bers are reserved by I ANA for special purposes
( see t he I ANA websit e for m ore inform at ion) .
I n I Pv6, m ult icast addresses provide t he sam e funct ionalit y as I Pv4 broadcast addresses.
Broadcast ing is not support ed in I Pv6. A m ult icast address allows a host t o send packet s t o all host s
in a m ult icast group. Mult icast scope allows you t o det erm ine t he size of t he m ult icast group. A
m ult icast address has a predefined prefix of ff00: : / 8.
23.1.2 IGMP Filtering
Wit h t he I GMP filt ering feat ure, you can cont rol which I GMP groups a subscriber on a port can j oin.
This allows you t o cont rol t he dist ribut ion of m ult icast services ( such as cont ent inform at ion
dist ribut ion) based on service plans and t ypes of subscript ion.
You can set t he Swit ch t o filt er t he m ult icast group j oin report s on a per- port basis by configuring
an I GMP filt ering profile and associat ing t he profile t o a port .
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Multicast