300-320 Question #79: Real Exam Question with Answer & Explanation

The correct answer is C: Minimize the number of areas supported by an ABR.. Minimizing the number of areas supported by an ABR (C) is a key OSPF scalability best practice. An ABR (Area Border Router) must maintain a separate Link-State Database (LSDB) for each area it connects to and must run the SPF algorithm for each. The more areas an ABR spans, the h

Question

Which practice is recommended when designing scalable OSPF networks?

Options

AMaximize the number of routers in an area.
BMinimize the number of ABRs.
CMinimize the number of areas supported by an ABR.
DMaximize the number of router adjacencies.

Explanation

Minimizing the number of areas supported by an ABR (C) is a key OSPF scalability best practice. An ABR (Area Border Router) must maintain a separate Link-State Database (LSDB) for each area it connects to and must run the SPF algorithm for each. The more areas an ABR spans, the heavier the CPU and memory burden, and the greater the inter-area route computation complexity. Cisco recommends an ABR connect to no more than 2–3 areas. Maximizing routers per area (A) and maximizing adjacencies (D) both increase LSA flooding and SPF computation, while minimizing ABRs entirely (B) conflicts with the need for hierarchical multi-area design.

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