5-5 - Implement Multicast LDP for Layer 3 Multicast MPLS VPN

Question 1

T/F: The MLDP-based MVPN feature provides extensions to Label Distribution Protocol (LDP) for the setup of point-to-multipoint and multipoint-to-multipoint LSPs for transport in the MVPN core network.

Answer 1

True

Question 2

Describe MLDP and its benefits.

Answer 2

• MLDP enables the use of a single MPLS forwarding plane for both unicast and multicast traffic.
• It also enables you to use existing MPLS protection (for example, MPLS Traffic Engineering/Resource Reservation Protocol (TE/RSVP link protection) and MPLS Operations Administration and Maintenance (OAM) mechanisms for multicast traffic.
• Lastly, it reduces operational complexity by eliminating the need for PIM in the MPLS core network.

Question 3

T/F: You can configure the threshold at which the data MDT is created on a per-device or a per-VRF basis.

Answer 3

True. When the multicast transmission exceeds the defined threshold, the sending PE device creates the data MDT and sends a UDP message, which contains information about the data MDT to all devices on the default MDT.

Question 4

T/F: Data MDTs are created only for (*, G) multicast route entries within the VRF multicast routing table.

Answer 4

False. Data MDTs are created only for (S, G) multicast route entries within the VRF multicast routing table. They are not created for (*, G) entries, regardless of the value of the individual source data rate.

Question 5

Describe how MLDP creates MDTs.

Answer 5

• The default MDT uses MP2MP LSPs. This usage supports low bandwidth and controls traffic between VRFs.
• The data MDT uses point-to-multipoint LSPs. This usage supports a single high-bandwidth source stream from a VRF.

Question 6

T/F: When using MLDP, you replace the MDT group address in the mGRE solution with a VPN ID

Answer 6

True

Question 7

IOS/IOS-XE Commands:
Device> enable
Device# configure terminal
Device(config)# mpls mldp logging notifications
Device(config)# mpls mldp forwarding recursive
Device(config)# mpls mldp path multipath downstream

Answer 7

This process includes configuring the following:
- MLDP logging notifications
- MLDP recursive forwarding over a point-to-multipoint LSP
- Load-balancing different LSPs over available paths or TE tunnels

Question 8

IOS/IOS-XE Commands:
Device(config)# ip multicast-routing
Device(config)# ip multicast-routing vrf VRF
Device(config-vrf)# ip vrf VRF
Device(config-vrf)# rd 50:11
Device(config-vrf)# vpn id 50:10
Device(config-vrf)# route target export 100:100
Device(config-vrf)# route target import 100:100
Device(config-vrf)# mdt preference mldp
Device(config-vrf)# mdt default mpls mldp 172.30.20.1
Device(config-vrf)# mdt data mpls mldp 255
Device(config-vrf)# mdt data threshold 40 list 1

Answer 8

This process includes configuring the following IP multicast routing for the MVPN VRF settings:
- Define the VRF instance
- Create a route distributor (RD) to make the VRF functional
- Set MLDP for MDT type
- Define default MDT group parameters, including root node
- Define data MDT parameters

Question 9

IOS/IOS-XE Command:
show mpls mldp database

Answer 9

displays information in the MLDP database
- Forwarding Equivalence Class (FEC) type
- Opaque value of the FEC decoded length and value
- FEC status
- Upstream clients
- Associated replication clients

Question 10

IOS/IOS-XE Command:
show ip pim vrf VRF neighbor

Answer 10

lists the PIM VRF neighbors

Question 11

IOS/IOS-XE Command:
show ip mroute vrf <VRF></VRF>

Answer 11

lists the mroutes for a given VRF

Question 12

IOS/IOS-XE Command:
show adjacency <lspvif0></lspvif0>

Answer 12

displays the output of the show adjacency command for the specified LSP-VIF interface

Question 13

IOS/IOS-XE Command:
show mpls forwarding-table | include <1F00001>

Answer 13

display the specified LSP-VIF interface entries in the MPLS Label Forwarding Information Base (LFIB)

Question 14

There are different ways a Label Switched Path (LSP) built by mLDP can be used depending on the requirement and nature of the application, such as the following:

Answer 14

• Point-to-multipoint LSPs for global table transit Multicast using in-band signaling.
• P2MP/MP2MP LSPs for MVPN based on MI-PMSI or Multidirectional Inclusive Provider Multicast Service Instance (Rosen Draft).
• P2MP/MP2MP LSPs for MVPN based on MS-PMSI or Multidirectional Selective Provider Multicast Service Instance (Partitioned E-LAN).

Question 15

The router performs the following important functions for the implementation of MLDP:

Answer 15

• Encapsulating VRF multicast IP packet with GRE/Label and replicating to core interfaces (imposition node).
• Replicating multicast label packets to different interfaces with different labels (Mid node).
• Decapsulate and replicate label packets into VRF interfaces (Disposition node).

Question 16

IOS-XR Command:
configure
multicast-routing vrf <vrf_name>
address-family ipv4
mdt default mldp ipv4 <root-node></root-node></vrf_name>

Answer 16

Configure MVPN routing and forwarding instance.

Question 17

IOS-XR Command:
configure
router bgp <AS>
vrf <vrf_name>
rd <rd_value></rd_value></vrf_name></AS>

Answer 17

Configure the route distinguisher:

Question 18

IOS-XR Command:
configure
multicast-routing vrf <vrf_name>
address-family ipv4
mdt data <1-255></vrf_name>

Answer 18

Configuring data MDTs (optional)

Question 19

IOS-XR Command:
configure
router bgp <AS>
address-family ipv4 mdt</AS>

Answer 19

Configure BGP MDT address family

Question 20

IOS-XR Command:
configure
router bgp <AS>
address-family ipv4 mdt
neighbor <x.x.x.x>
address-family ipv4 mdt
next-hop-self</x.x.x.x></AS>

Answer 20

Configure neighbors for BGP MDT address family

Question 21

IOS-XR Command:
configure
router bgp <AS>
address-family vpnv4 unicast</AS>

Answer 21

Configure BGP VPNv4 address family

Question 22

IOS-XR Command:
configure
router bgp <AS>
vrf <vrf_name>
address-family ipv4 unicast</vrf_name></AS>

Answer 22

Configure BGP IPv4 VRF address family

Question 23

IOS-XR Command:
configure
router pim
vrf vrf_name
address-family ipv4
rpf topology route-policy <my-policy></my-policy>

Answer 23

Configure PIM SM/SSM Mode for the VRFs

Question 24

IOS-XR Command:
route-policy <my-policy>
set core-tree <tree-type>
pass
end-policy</tree-type></my-policy>

Answer 24

Configure route-policy

Question 25

IOS-XR Command:
show mpls mldp neighbors

Answer 25

verify the following aspects of MLDP neighbors:
- MLPD Peer ID: IP address and label space used as neighbor’s LDP ID
- Uptime: how long has been the neighbor in UP state
- Current State: UP, DOWN, other
- Neighbor capabilities: Graceful Restart (GR), point-to-multipoint, MP2MP, others
- Policy filter in: applied policy in
- Path count: number of paths to reach the neighbor
- Paths: list of connected neighbors and interfaces to reach them
- Adj list: list of LDP neighbor with established adjacencies
- Peer Adr list: List of IP addresses configured in neighbor

Question 26

IOS-XR Command:
show mpls mldp bindings

Answer 26

To display the contents of the multicast Label Information Base (LIB)

Question 27

Important core-tree type to know.

Answer 27

mldp-inband - lets you carry multicast traffic across an existing IP/MPLS backbone, while avoiding the use of PIM in the provider core.

Question 28

What is true about MLDP for Layer 3 multicast MPLS VPNs?

A. The MLDP-based MVPN feature provides extensions to LDP for the setup of point-to-multipoint and multipoint-to-multipoint LSPs for transport in the MVPN core network.
B. The default MDT provides support for high-bandwidth transmission from high-rate data sources.
C. PE devices use the MDT data to send multicast data and control messages to every other PE device in the multicast domain.
D. MLDP enables the use of two MPLS forwarding planes, one for unicast and the other for multicast traffic.

Answer 28

A