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IT infrastructuur > 13. Multicast > Flashcards

13. Multicast Flashcards

1
Q

What is Multicast?

A

A technology that optimizes network bandwith utilization and conserves system resources. Called one-to-many

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2
Q

What are the protocols for Multicast?

A

IGMP for layer 2

PIM for layer 3

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3
Q

What are the 2 disadvantages of Broadcast?

A
  • Not enabled by default on Cisco, enabling exposes to DDoS

- Nic’s of uninterested workstations must still process the broadcast packets

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4
Q

How does Multicast traffic operate?

A

Provides a single data packet that is replicated between links as the data forks on a network device along the Multicast Distribution Tree (MDT). A network device requests to receive the stream.

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5
Q

What is the multicast address range?

A

224.0.0.0 up to 239.255.255.255. First bits always start with 1110

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6
Q

What is the designation of the range 224.0.0.0/24?

A

Local network control block

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7
Q

What is the designation of the range 224.0.1.0/24?

A

Internetwork control block

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8
Q

What is the designation of the range 232.0.0.0/8?

A

Source Specific Multicast block

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9
Q

What is the designation of the range 233.0.0.0/8?

A

GLOP block

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10
Q

What is the designation of the range 239.0.0.0/8?

A

Administratively scoped block

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11
Q

Where does the 24-bits Multicast MAC starts with?

A

01:00:5E

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12
Q

Which bit is always 0 and wich always 1 with Multicast?

A

The 25th bit is always 0

The 8th bit is always 1

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13
Q

How are the lowest 23 bits calculated?

A

Copied from the Multicast IP

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14
Q

How does a receiver request for a specific Multicast feed?

A

It sends a IGMP join using the multicast IP for that feed. The receivers reprograms the interface with the corresponding MAC address

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15
Q

What is IGMP?

A

Internet Group Management Protocol. Used by receivers to join and start receiving traffic from multicast groups.

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16
Q

How many versions of IGMP are there?

A

3 versions

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17
Q

What is the IGMPv2 process?

A
  • Receiver send IGMP join to local router with wanted group
  • Router forwards upstream with PIM
  • Stream begins
  • Router sends periodically membership query messages with max timer
  • Receivers waits timer and sends a membership report
  • If a receiver receives a report whilst the timer is running it prevents sending duplicate reports
  • Receiver that wants to leave ssends a message to 244.0.0.2 if it was the last receiver to respond
  • Router sends a memberships query to the group multicast to see if there are still receivers left. If not it removes the IGMP state for the group
18
Q

What happens when there are more IGMPv2 routers in the LAN segment?

A

A querier election takes place. General membership message are send to 244.0.0.1. Lowest IP wins.

A timer reset when memberships queries are received.

19
Q

What happens when querier routers stops sending queries?

A

Non-querier routers wait twice the wait tie (default 60 sec). If nothing comes the election begins again.

20
Q

What are the 5 IGMPv2 messages?

A 
V2 membership report - join
V1 membership report - backwards v2
V2 leave group - leave
General membership query - 224.0.0.1 check members
Group specific query - Reply to leave
21
Q

What are the 2 extra modes of IGMPv3?

A

Include and exclude

22
Q

What is IGMP snooping?

A

The switch rememers the interfaces from where the join messages came from

23
Q

What is PIM?

A

Protocol Independent Multicast, the only multicast protocol Cisco supports.

24
Q

What are the 2 types of distribution trees?

A 
Source trees (SPT, shortest path tree)
Shared trees (RPT, rendezvous point tree)
25
Q

How do multicast routers reach the receivers?

A

Multicast routers create distribution trees that define the past IP multicast traffic follows

26
Q

How do source trees work?

A

The source (Server) is the root of the tree and the branches form the distribution tree. Know as Source comma Group.

27
Q

How do shared trees work?

A

The root is a router designated as the rendezvous point

28
Q

What is the Reserve Path Forwarding (RPF) interface?

A

Interface with the lowest metric to the IP address of the source (SPT) or RP. Even equal the highest IP.

29
Q

What is the RPF neighbor?

A

The PIM neighbor on the RPF interface

30
Q

What is the upstream interface?

A

The interface towards the source of the stream, also known as incoming interface.

31
Q

What is the downstream interface?

A

The interface backwards the source of the stream, also known as outgoing interface, also known as outgoing interface

32
Q

What is the outgoing interface list?

A

Group of OIFs that are forwarding multicast traffic to the same group.

33
Q

What is the last hop router (LHR)?

A

The router that is directly attached to the receiver. Known as the leaf router.

34
Q

What is the first hop router (FHR)?

A

The router that is directly attached to the source. Responsible for sending register messages to the RP.

35
Q

What is the Multicast Routing Information Base (MRIB?

A

Topology table which derives from the unicast table and PIM

36
Q

What is the Multicast Forwarding Information Base (MFIB?

A

Uses the MRIB for faster hardware forwarding

37
Q

What are the 5 PIM operating modes?

A 
PIM Dense mode
PIM Sparse mode
PIM Sparse Dense
PIM Source Specific Multicast
PIM Bedirectional Mode
38
Q

What is the protocol number of PIM?

A

103

39
Q

What type are the control messages of PIM?

A

Unicast (register and register stop messages)

Multicast (TTL 1 to 244.0.0.13)

40
Q

What is the default time for PIM Hellos?

A

30 seconds

41
Q

What are the 9 types of PIM messages?

A 
Hello
Register
Register stop
Join/prune
Bootstrap
Assert
Candidate RP advertisement
State Refresh
DF election

IT infrastructuur (31 decks)

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