Multicast

Question 1

What is multicast traffic?

Answer 1

One to many communication.

Question 2

What is the multicast IP address range?

Answer 2

224. 0.0.0 /4

224. 0.0.0 - 239.255.255.255

Question 3

What is the multicast IP address range?

Answer 3

224. 0.0.0 /4

224. 0.0.0 - 239.255.255.255

Question 4

What is the ‘Local Network Control Block’ for multicast addresses?

Answer 4

224.0.0.0 /24

addresses in this block do not leave the L2 broadcast domain.

Question 5

What is the ‘Internetwork Control Block’ in multicast?

Answer 5

224.0.1.0 /24

This block can be routed over the internet

Question 6

What is the ‘administratively scoped block’ in multicast?

Answer 6

239.0.0.0 /8

This is the private multicast range (not publicly routed)

Question 7

How do you differentiate between unicast and multicast Mac addresses?

Answer 7

Unicast have an even or zeroed second digit

Multicast are always an odd digit

0200 - unicast

0100 - multicast

Question 8

What is multicast MAC 0100.0CCC.CCCC reserved for?

Answer 8

CDP, VTP and UDLD

Question 9

What is multicast MAC 0100.0CCC.CCCD reserved for?

Answer 9

RSTP

Question 10

What is multicast MAC 0180.C200.0000 reserved for?

Answer 10

802.1D spanning tree

Question 11

What MAC address range is reserved for IPv4 Multicast?

Answer 11

100. 5E00.000 ->

0100. 5E7F.FFFF

Question 12

What is the broadcast MAC address for a subnets broadcast IP?

Answer 12

FFFF.FFFF.FFFF

Question 13

What does IGMP stand for?

Answer 13

Internet Group Management Protocol

Question 14

What is IGMP used for?

Answer 14

IGMP is used between receiving devices and their next hop gateway to instruct multicast routers which multicast groups they would like to receive.

Question 15

What is an IGMP multicast report?

Answer 15

It is the message sent from a receiving device to the multicast address group it would like to join.

Question 16

How does a receiver leave a multicast group?

Answer 16

They send a ‘Leave Group’ message to their next hop router.

Question 17

What is a IGMP Membership Query?

Answer 17

It is the message sent by a next hop router to determine which hosts would like to receive multicast traffic.

They are sent every 60 seconds to multicast address 224.0.0.1 (TTL 1)

Question 18

What IP protocol number field does IGMP use?

Answer 18

IP protocol number 2

Question 19

What is IGMP snooping?

Answer 19

The mechanism in which Cisco switch’s learn which switch ports must forward multicast traffic

Question 20

How does IGMP snooping work?

Answer 20

The switch will sniff IGMP membership reports increasing a switch port. this mapping is stored in the CAM table for later forwarding.

It will remove the entry when a IGMP leave message is detected.

Question 21

What does PIM stand for?

Answer 21

Protocol Independent Multicast

It is a multicast routing protocol.

Question 22

How does PIM dense mode work?

Answer 22

The router will default flood all multicast traffic except the receiving port.

If the receiving router or downstream routers have no multicast group members, they send a prune message to end communication.

If the link has been pruned, downstream routers can send a upstream Graft message to reestablish forwarding.

Question 23

How does PIM sparse mode work?

Answer 23

Routers by default will forward no multicast traffic.

Downstream routers will initiate a connection with a PIM join request after receiving IGMP meme verschul reports.

When a router no longer needs the multicast traffic, it will send a upstream prune message.

Question 24

What multicast address and IP number does PIM use for hello messages?

Answer 24

224.0.0.13

IP 103