5-2 - Multicast VPN Fundamentals

Question 1

T/F: MPLS natively has the ability to support multicast.

Answer 1

False.
MPLS has no native ability to support multicast.

Question 2

T/F: Multicast VPN uses VRFs for each customer and then looks for ways to transport the multicast traffic through the service provider core.

Answer 2

True

Question 3

Describe the two ways that multicast VPN traffic can transport over the core network.

Answer 3

• Rosen GRE (native)
  *uses GRE with unique multicast distribution tree (MDT) forwarding to enable scalability of native IP Multicast in the core network
• MLDP
  *an extension to LDP that provides support for the setup of P2MP and MP2MP LSPs that can be used to support multicast in MPLS VPN environments

Question 4

Describe the multicast distribution tree (MDT).

Answer 4

• MVPN establishes a static default Multicast Distribution Tree (MDT) for each multicast domain.
• defines the path that PE routers use to send multicast data and control messages to other PE routers in the multicast domain

Question 5

Describe multicast tunnel interfaces (MTI)

Answer 5

• a tunnel interface that sources all MVRF traffic
• One tunnel interface is created per MVRF.

Question 6

Describe Multicast Distributed Switching (MDS) for Multicast VPN

Answer 6

• uses a forwarding data structure called a Multicast FIB (MFIB)
• enabled globally and on a per interface basis

Question 7

Describe MDT Address Family in BGP for Multicast VPN

Answer 7

• You add the “mdt” keyword to the address-family ipv4 command to configure an MDT address-family session.
• You use MDT address-family sessions to pass the source PE address and MDT group address to PIM by using BGP MDT Sub-address Family Identifier (SAFI) updates.

Question 8

What is true about Layer 3 Multicast VPNs?

A. MVPN is implemented without using VRF tables for the customer.
B. MVPN with Layer 3 VPN allows service providers to offer multicast connectivity.
C. Enterprise traffic entering the service provider domain routes based on the global routing table.
D. MPLS labels are unnecessary to ensure proper tunneling and demultiplexing.

Answer 8

B

Question 9

Describe the default MDT group.

Answer 9

The Default-MDT is always used to send multicast control traffic between PE routers in a multicast domain.

Question 10

Describe the Data MDT group.

Answer 10

A special MDT group called a Data-MDT can be created to minimize the flooding by sending data only to PE routers that have active VPN receivers. The Data-MDT is created dynamically if a particular multicast stream exceeds a bandwidth threshold. Each VRF can have a pool of Data-MDT groups allocated to it.