Cisco ENCOR (MPLS) 5

Question 1

Which Cisco IOS command enables MPLS forwarding on a specific interface?

Accepted Answer

mpls ip

Answer

The interface-level command 'mpls ip' enables MPLS forwarding and LDP label distribution on that interface.

Question 2

What is the MPLS EXP (experimental) field in a label entry now officially renamed to in RFC 5462?

Accepted Answer

Traffic Class (TC) bits

Answer

RFC 5462 renamed the MPLS EXP field to Traffic Class (TC) bits, reflecting its primary use for QoS marking in MPLS networks.

Question 3

In MPLS L2VPN, what is an 'attachment circuit' (AC)?

Accepted Answer

The physical or logical interface connecting a CE to a PE

Answer

An attachment circuit is the physical or logical link between a CE device and the PE router, carrying customer L2 traffic into the MPLS network.

Question 4

Which protocol is used to signal pseudowires in MPLS-based L2VPN services (AToM)?

Accepted Answer

LDP (targeted)

Answer

AToM (Any Transport over MPLS) uses targeted LDP sessions between PEs to signal and establish pseudowires for L2VPN services.

Question 5

What does the MPLS 'TTL' field control in a label entry?

Accepted Answer

Hop count to prevent routing loops, decremented at each LSR

Answer

The 8-bit TTL field in each MPLS label is decremented at each LSR to prevent forwarding loops, similar to the IP TTL field.

Cisco ENCOR Practice Test