Which two statements about MPLS L3 VPN RDs are true? (Choose two.)

Question

Options

• AThey enable EIGRP to use address families to separate traffic between IPv4 and VPNv4.
• BThey are represented as 32-bit values
• CThey are represented as 64-bit values.
• DThey enable OSPF to import and export routes into the global routing table of a router.
• EThey allow BGP to uniquely identify duplicate routes.

• A
  9% (5)
• B
  14% (8)
• C
  76% (44)
• D
  2% (1)

Explanation

Route Distinguishers (RDs) are 64-bit values (option C) prepended to IPv4 prefixes to create unique VPNv4 routes in MPLS L3 VPN. This solves the overlapping address problem: when two VPN customers use the same private IP space (e.g., 10.0.0.0/8), BGP can uniquely identify each customer's route (option E) by distinguishing them via different RDs - making duplicate prefixes appear as distinct BGP routes.

Why the distractors are wrong:

• A - EIGRP address families and their IPv4/VPNv4 separation are unrelated to RDs; RDs are a BGP/MPLS mechanism.
• B - RDs are 64-bit, not 32-bit. (32-bit describes a standard IPv4 address or an ASN in older notation.)
• D - OSPF route import/export into the global table is the job of Route Targets (RTs), not RDs. RDs and RTs are commonly confused but serve different purposes.

Memory tip: Think RD = Route Distinguisher → it distinguishes (makes unique) duplicate routes for BGP. RT = Route Target → it targets which VRFs to import/export routes into. RDs are always 64-bit (typically formatted as ASN:nn or IP:nn, both totaling 8 bytes = 64 bits).

No community discussion yet for this question.