Q) What is Multicast?
A: Multicast is a method of sending the data from one source to so many receivers.
Q) What are the protocols used in Multicast?
A: IGMP - Provides the communication between host and Router
PIM(IPV4), MLD(IPV6)- Provides the communication between Router and Router
IGMP Snooping & CGMP - Provides the communication between Router & Switch
Q) What is IGMP?
A: IGMP is a protocol which enables the host to join particular group by signalling the router.
Q) What is the difference between IGMPV1 and IGMPv2?
A: --> In IGMPV1 there are only 2 messages are used ( Membership Query and Membership Report) whereas in IGMPV2 there is one more message extra( Query, Report and Leave).
--> In IGMPV1 there is no Group Membership Query message.
--> There is no Querier Election mechanism in IGMPV1.
Q) What is the use of Multicast Distribution Tree?
A: Multicast Distribution Tree specifies the path between source and Receiver in which multicast traffic should be forwarded. There are mainly two types of Multicast Distribution Trees
1) Source Tree
2) Shared Tree
Q) What is the Source Tree ?
A: Source Tree
--> Used in both PIM Sparse Mode and Dense Mode.
--> Uses Source as the Root of the Multicast Tree and Receivers are acting like branches.
--> It is also known as Shortest Path Tree because it uses the shortest path between source and receiver.
--> Every Router in Source Tree will add (S,G) Entries in multicast routing table.
Where S = Source or Sender IP address ( Unicast) (192.1.1.1)
G = Destination IP address ( Multicast IP address) (224.5.5.5)
Q) What is the Shared Tree?
-> Used in both PIM Sparse Mode only.
--> Uses Rendezvous Point as the Root of the Multicast Tree and shortest path tree will be created between i) Source & RP ii) Receiver & RP
--> It is also known as Root Path Tree or Core Based Tree.
--> Every Router in Source Tree will add (*,G) Entries in multicast routing table.
Where * = All Sources
G = Destination IP address ( Multicast IP address) (224.5.5.5)
Q) What is PIM?
A: PIM is a protocol used between the routers to forward multicast traffic. PIM works in two modes
i) PIM Dense Mode
ii) PIM Sparse Mode
Q) What are the different types of Multicast Address Ranges?
Link-Local Multicast Address:
--> Link-Local Multicast address range is reserved with 224.0.0.0/24
--> They have the TTL Value of 1.
--> Multicast packet cannot be forwarded outside of the link.
--> Mostly used in routing protocols such as EIGRP/OSPF for sending hello packets.
Ex: 224.0.0.5 --> OSPF, 224.0.0.10 --> EIGRP
Source-Specific Multicast
--> Source-Specific Multicast address range is reserved with 232.0.0.0/8
--> Used for Discovering the unicast address of the server who is generating the multicast traffic.
GLOP Multicast Address
--> GLOP Multicast address range is reserved with 233.0.0.0/8
--> GLOP has no abbreviation, it is just GLOP.
--> GLOP Multicast address is used by companies who have their own Public AS Number.
--> If a company owns Public AS Number 21544 then in order to get the Multicast address for the company:
1) Convert the AS Number from Decimal to Hexa Decimal
21544 --> 5428
2) Convert Hexa Decimal of the first two digits 54 to Decimal and the last two digits 28 to Decimal.
54 --> 84 and 28 --> 40
3) The Multicast Address would be 233.84.40.0/24 for company X.
Private Multicast Address
--> Source-Specific Multicast address range is reserved with 239.0.0.0/8
--> It is similar to a Private IP address in IPv4 address.
--> It is also known as administratively scoped address.
--> Traffic is never routed on the Internet.
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