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CCNP Core > Chap 13 - Multicast (part 2) > Flashcards

Chap 13 - Multicast (part 2) Flashcards

1
Q

What are the 2 type of Multicast Distribution Trees?

A
  • Shortest Path Trees (SPT) aka Source Trees
  • Shared Trees
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2
Q

What is a Source Tree or Shortest Path Tree?

A
  • Source is the root of the tree
  • Tree is built using the Shortest Path from the Source to the leaves of the tree
  • Every multicast Source needs a SPT because every Source is the root of the tree. Different source, different tree.
  • Uses S, G notation
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3
Q

What is meant by S,G notation?

A

It’s a way of describing the forwarding state of a SPT. S, G stands for Source IP address, Group IP address (ex. 10.1.1.2, 239.1.1.1)

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4
Q

What is meant by *, G notation?

A

It’s a way of describing the forwarding state of a Shared Tree, also known as a Rendezvous Point Tree (RPT)

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5
Q

What is a Shared Tree?

A
  • aka Rendezvous Point Tree (RPT)
  • Multicast traffic is forwarded down the Shared Tree according to the Group Address that the packets are addressed to
  • Has a router known as a RP or Rendezvous Point
  • Uses *,G notation with * meaning any source and G meaning the Group IP address
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6
Q

What is an advantage of a Shared Tree (RPT)?

A

They require fewer multicast entries.

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7
Q

What are the disadvantages of a Shared Tree?

A
  • Receivers receive traffic from ALL sources even if they are sending traffic to the same Multicast address thereby wasting bandwidth
  • Network security issues since any source can send what may be unwanted traffic
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8
Q

What is an RPF?

A
  • Reverse Path Forwarding Interface
  • The interface with the lowest-cost path (administrative distance and metric) to the address of the source (SPT) or Rendezvous Point (RPT)
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9
Q

When identifying an RFP interface and multiple interfaces have the same metric what is the tie-breaker?

A

Interface with the Highest IP address wins

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10
Q

What is an RPF neighbor?

A

The neighbor of the RPF interface.

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11
Q

What is Upstream?

A

Upstream is toward the source or if RPT upstream would be in the direction of the RP router

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12
Q

What is an Upstream Interface?

A

Another name for the RPF interface aka IIF (Incoming Interface)

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13
Q

What is Downstream?

A

In the direction AWAY from the source and toward the Receiver

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14
Q

What is a Downstream Interface?

A

Any interface used to forward traffic away from the source aka OIF or Outgoing Interface

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15
Q

What is the Incoming Interface?

A
  • IIF
  • aka RPF
  • The only type of interface that can accept traffic coming from the source
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16
Q

What is an Outgoing Interface List?

A
  • OIL
  • A group of Outgoing Interfaces that are forwarding traffic to the same group
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17
Q

What is a Last Hop Router?

A
  • LHR - A router that is directly attached to receivers
  • aka Leaf Router
  • Its responsible for sending PIM Joins upstream toward the RP or the Source
18
Q

What is a First Hop Router?

A
  • FHR
  • aka Root Router
  • A router that is directly attached to the source
  • It is responsible for sending Register Messages to the RP
19
Q

What is the Multicast Routing Information Base?

A
  • aka Multicast Route Table
  • aka MRIB
  • aka mroute
  • Topology table derived from the unicast routing table and PIM.
20
Q

What is in the mroute table?

A
  • For every multicast route it contains
  • The S, G, Source, Group info
  • Incoming Interfaces (IIF)
  • Outgoing Interfaces (OIF)
  • RPF Neighbor info
21
Q

What is the Multicast Forwarding Table?

A
  • MFIB
  • A forwarding table that uses MRIB to program multicast forwarding info in hardware for faster forwarding
22
Q

What is the Multicast State?

A
  • Multicast forwarding state that is used by the router to forward multicast traffic
  • Multicast state is composed of entries found in the mroute table (S, G, IIF, OIF, etc)
23
Q

What are the 5 PIM Operating Modes?

A
  • PIM Dense Mode (PIM-DM)
  • PIM Sparse Mode (PIM-SM)
  • PIM Sparse Dense Mode
  • PIM Source Specific Multicast (PIM-SSM)
  • PIM Bi-directional mode (Bidir-PIM)
24
Q

Whis is another name for PIM-DM and PIM-SM?

A

Any Source Multicast (ASM)

25
Q

What are the 9 PIM Control Messages along with their message types?

A
  • Type 0 - Hello
  • Type 1 - Register
  • Type 2 - Register Stop
  • Type 3 - Join/Prune
  • Type 4 - Bootstrap
  • Type 5 - Assert
  • Type 8 - Candidate RP Advertisement
  • Type 9 - State Refresh
  • Type 10 - DF Election
26
Q

What is the PIM Hello message used for and how often is it sent?

A
  • It is sent out all PIM-enabled interfaces every 30 seconds by default
  • It is used to detect other PIM routers
  • It is also used to elect a Designated Router
27
Q

Who sends the PIM Register message and what is it used for?

A
  • A FHR will send the RP a unicast Register message when it detects a new multicast source
  • It is sent to let the RP know about the new source
28
Q

Who sends the PIM Register Stop message, where is it sent to, and what is its purpose?

A
  • Sent by the RP to FHR with unicast
  • Used to stop the register messages when the RP either doesn’t have a subscriber to the source or when the SPT between the source and the RP has been built
29
Q

What are 2 times when the PIM Join/Prune message is sent, and what are its purposes ?

A
  • This is sent by a PIM router when it gets a membership report from a host and is then relayed by other PIM routers until it gets to the source or RP
  • It is also sent by a PM router when it wants to stop a multicast stream
  • Sent to 224.0.0.13 (all PIM routers)
30
Q

Who sends the PIM Bootstrap message, what is its destination, and what does it contain?

A
  • Sent by Bootstrap router
  • Sent to 224.0.0.13 (all PIM routers) with TTL of 1
  • Contains information about the BSR and RP-to-group mappings
31
Q

When is the PIM Assert message sent and what does it cause to happen?

A
  • This is sent by a PIM router when it detects multicast traffic from another PIM router on the same subnet.
  • It is used to facilitate an election between the 2 to decide who the PIM Forwarder will be. (Winner has best AD, then metric, then highest IP address)
32
Q

What is the PIM Candidate RP Advertisement?

A
  • Sent by a router that wants to be an RP
  • Sent to Bootstrap Router (BSR) in unicast
33
Q

What is the PIM State Refresh message?

A

This message keeps the pruned state in PIM dense mode from timing out, which saves network bandwidth by greatly reducing the reflooding of unwanted multicast traffic to pruned branches of the PIM dense mode network

34
Q

When is PIM-DM used?

A

When there are a lot of receivers on the network.

35
Q

What 3 steps describe how is a PIM-DM tree built?

A
  • When a multicast stream starts it is flooded out to every PIM-DM router in the network.
  • The tree takes shape as routers decide if they have any receivers
  • If not, they send Prune messages and the flooding stops for that router
36
Q

Which interface is allowed to accept multicast flooding?

A

The RPF interface

37
Q

In PIM-DM, what happens if a router receives multicast flooding on a non-RPF interface?

A
  • Router discards the traffic on that interface
  • Sends the neighbor a Prune message to stop the flooding.
38
Q

In PIM-DM when do Prunes expire?

A

Every 3 minutes

39
Q

How often is a PIM-DM multicast tree rebuilt?

A

Every 3 minutes

40
Q

In PIM-DM what remains on a router even after it has been pruned?

A

The S, G state remains on the router.

CCNP Core (46 decks)

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