A network administrator is teaching a junior engineer about MPLS Layer 3 VPNs. The administrator is explaining that a label stack is required for an MPLS domain to forward traffic. Which statement is accurate about a label stack?

A network administrator is teaching a junior engineer about MPLS Layer 3 VPNs. The administrator is explaining that a label stack is required for an MPLS domain to forward traffic. Which statement is accurate about a label stack?

• The LDP label is used by the egress router to determine customer specifics about the packet.
• VPN labels are learned from PE routers over the MP-IBGP peering.
• When the IP packet leaves the egress PE router, the VPN and LDP labels are attached to the IP packet.
• There are two labels attached to the IP packet; the first one is an LDP label, and the second one is the VPN label.

Explanation: Specifically, two labels are required for traffic to be successfully forwarded through the MPLS domain. The VPN label is the first label attached to the packet, and the LDP label is the second. The PE router attaches both labels when the IP packet arrives at the ingress PE router. The egress router uses the VPN label to determine customer specifics about the packet and what should be done with it. The LDP label is used for label switching from PE to PE in the MPLS domain. VPN labels are learned from PE routers over the MP-IBGP peering.

Exam with this question: CCNP ENARSI v8 Certification Practice Exam