300-420 Question #79: Real Exam Question with Answer & Explanation

Question

In a simple MPLS L3VPN, which two tasks are performed by the PE router? (Choose two.)

Options

• AIt establishes pseudo wires with other PEs.
• BIt exchanges VPNv4 and VPNv6 routes with CE Devices.
• CIt assigns labels to routes in individual VPNs.
• DIt forwards labeled packets to CE devices.
• EIt exchanges VPNv4 or VPNv6 route with other PE routers.

Explanation

In an MPLS L3VPN, PE routers are responsible for assigning labels to routes within individual VPNs and exchanging these VPNv4/VPNv6 routes with other PE routers.

Common mistakes.

• A. Pseudo wires are typically associated with Layer 2 VPNs (L2VPNs), not the core functionality of a simple MPLS L3VPN.
• B. PE routers exchange standard IPv4 or IPv6 routes with CE devices, while VPNv4/VPNv6 routes are exchanged exclusively between PE routers.
• D. PE routers forward labeled packets into the MPLS core from CE devices and forward unlabeled packets to CE devices after stripping the MPLS labels.

Concept tested. MPLS L3VPN PE router functions

Reference. https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/mp_l3_vpns/configuration/15-mt/mp-l3-vpns-15-mt-book/mp-l3-vpns-cfg.html

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