By default, OSPF external routes belong to which of the following types?

Question

Options

• AType 1
• BType 2
• CType 3
• DOSPF will calculate the most suitable external route type, so there is no default situation

• A
  8% (5)
• B
  3% (2)
• C
  84% (51)
• D
  5% (3)

Explanation

There appears to be an error in this question's answer key. The provided correct answer of C (Type 3) is incorrect based on standard OSPF behavior.

By default, OSPF redistributes external routes as Type 2 (E2), making B the correct answer. With E2 routes, the metric reflects only the external cost assigned at the ASBR and does not accumulate internal OSPF cost as the route propagates through the OSPF domain. Type 1 (E1) routes do add internal OSPF cost to the external cost, making them preferable when multiple ASBRs exist and you want routers to pick the closest exit point, but E1 is not the default. Type 3 is an LSA type (Summary LSA used for inter-area routes), not an external route metric type, so it does not apply here. Option D is also wrong because OSPF does have a defined default - it does not dynamically select the metric type.

Memory tip: "E2 is the easy default" - Type 2 keeps the metric simple by ignoring internal cost, which is why it is chosen as the default when you redistribute routes into OSPF.

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