MPLS

Question 1

At which layer of the OSI model does MPLS operate?

Answer 1

Between Layer 2 and Layer 3 (often called “Layer 2.5”)

Question 2

What does MPLS use instead of IP addresses to forward packets?

Answer 2

Labels

Question 3

What is the name of the unidirectional path an MPLS packet follows?

Answer 3

Label Switched Path (LSP)

Question 4

Which router assigns the first label to an MPLS packet?

Answer 4

Ingress Label Edge Router (LER)

Question 5

What router removes the label from an MPLS packet?

Answer 5

Egress Label Edge Router (LER)

Question 6

What protocol is commonly used to exchange MPLS labels?

Answer 6

Label Distribution Protocol (LDP)

Question 7

How many bits are in an MPLS label?

Answer 7

32 bits

Question 8

What field in the MPLS label indicates if it’s the last label in the stack?

Answer 8

Bottom of Stack (S-bit)

Question 9

True or False: MPLS can carry only IPv4 traffic.

Answer 9

False – MPLS is multiprotocol (IPv4, IPv6, Ethernet, etc.)

Question 10

What benefit does MPLS offer for routing voice or video traffic?

Answer 10

Supports Quality of Service (QoS)

Question 11

MPLS VPNs most commonly operate at which OSI layer?

Answer 11

Layer 3

Question 12

What is the role of a Label Switch Router (LSR)?

Answer 12

Forwards MPLS packets based on labels

Question 13

What MPLS feature allows routing along non-shortest paths for load balancing or policy routing?

Answer 13

Traffic Engineering (TE)

Question 14

Does MPLS increase or decrease convergence time in the network?

Answer 14

Decrease – allows fast reroute in case of failure.

Question 15

Is MPLS typically used in home networks?

Answer 15

No – it’s used in enterprise and service provider networks.