Multicast

Question 1

What do PIM message packets look like?

Answer 1

Protocol 103.
4 bits   - PIM Ver
4 bits   - Type
8 bits   - Reserved
16 bits - Checksum

Messages are either unicast or multicast to 224.0.0.13 / ff02::d.

Question 2

What function does the BSR provide?

Answer 2

Discovery:
Floods BSR messages to all routers.
Listens for BSR messages and if a higher priority message is received gives up it’s role of BSR. Eventually there is only 1 BSR per domain.

RP Discovery:
Every RP unicasts its own address and configured ranges to the BSR.
The BSR then floods a list of group range to RP maps to all PIM routers.

Question 3

Are lower or higher PIM RP-candidate priorities preferred?

Answer 3

Lower - default is 0!

Question 4

What is the PIM RP-Candidate tie breaker if all priorities are the same?

Answer 4

IP Address - Higher is preferred!

Question 5

Who selects the best RP from a list of candidates when using BSR?

Answer 5

Each router selects from the advertised group range to RP maps.

Question 6

What are the 4 steps for C-RP selection?

Answer 6

1. Select longest match group prefix from C-RP list.
2. If more than 1 C-RP select lowest priority.
3. If more than 1 C-RP use BSR Hash function.
4. If more than 1 C-RP prefer highest IP.

Question 7

Which MLD version is similar to IGMPv2?`

Answer 7

Version 1.

Question 8

Which MLD version support SSM?

Answer 8

Version 2.

Question 9

Which protocol handles messages for MLD?

Answer 9

ICMPv6.

Question 10

Which 3 messages does MLD use?

Answer 10

• Query
• Report
• Done