QuestionQ97

Network Design

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Refer to the exhibit. An engineer is designing a multiarea OSPF network for a client that also has a large EIGRP domain. EIGRP routes are being redistributed into OSPF. OSPF area 20 contains routers with limited memory and CPU resources. The engineer wants to prevent routes from EIGRP 111 from propagating into area 20 while allowing EIGRP 222 routes to enter. Which OSPF area type meets this design requirement?

  • A type 3 LSA filtering on the ABR between area 0 and area 20
  • B type 5 LSA filtering on the ASBR between EIGRP 111 and area 0
  • C area 20 as a stub area
  • D area 20 as a NSSA area
Explanation

An NSSA blocks Type 5 external LSAs from other OSPF areas, preventing the EIGRP 111 routes redistributed in area 0 from entering area 20. It permits an ASBR within the NSSA to redistribute EIGRP 222 routes as Type 7 LSAs, which are valid inside the NSSA.

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