Which three functions are performed by the PE router in an MPLS Layer 3 VPN? (Choose three.)

Question

Options

• Aexchanges routing updates with the CE router
• Btranslates the CE routing information into VPNv4 routes
• Cexchanges VPNv4 routes with other PE routers over MP-BGP
• Dimports and exports RTs that are received from the P routers
• Eexchanges RDs with the P routers
• Fexchanges VPN labels with the CE routers

• A
  70% (21)
• D
  17% (5)
• E
  10% (3)
• F
  3% (1)

Explanation

In an MPLS L3 VPN, the PE router is the VPN "brain" - it bridges the customer world (CE routers) and the provider backbone (P routers and other PEs). A is correct because the PE must first learn customer routes by exchanging routing updates directly with the CE using standard protocols (BGP, OSPF, EIGRP, or static). B is correct because the PE then prepends a Route Distinguisher (RD) to those IPv4 prefixes, converting them into globally unique VPNv4 routes. C is correct because the PE advertises those VPNv4 routes to remote PEs using MP-BGP, carrying Route Targets (RTs) to control VPN membership.

Why the distractors are wrong:

• D is wrong: RTs are carried between PE routers via MP-BGP - P routers are label-only forwarders with zero VPN awareness and never handle RTs.
• E is wrong: RDs are locally assigned by each PE and embedded in VPNv4 prefixes; they are never "exchanged" with P routers.
• F is wrong: CE routers are MPLS-unaware - they only see plain IP. VPN labels are signaled between PE routers, not PE-to-CE.

Memory tip: The PE does three C's - Connect (peer with CE), Convert (IPv4 → VPNv4 with RD), Communicate (VPNv4 via MP-BGP to other PEs). Everything else - label swapping, P router interactions - stays inside the core and is invisible to VPN logic.

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