Refer to the exhibit, which shows an OSPF network. Which types of link-state advertisements (LSA) will NGFW-1 send, if it is a backup designated router (BDR)?

Question

Exhibit

Options

• ANGFW-1 will send type 1 and type 2 LSAs.
• BNGFW-1 will send type 1 and type 3 LSAs.
• CNGFW-1 will send type 1 and type 4 LSAs.
• DNGFW-1 will send type 1 and type 5 LSAs.

• A
  20% (3)
• B
  60% (9)
• C
  13% (2)
• D
  7% (1)

Explanation

Option B is correct because every OSPF router - regardless of role - generates Type 1 (Router) LSAs to describe its own links within an area, and since NGFW-1 also functions as an ABR (Area Border Router) connecting multiple OSPF areas (as shown in the exhibit topology), it generates Type 3 (Summary) LSAs to advertise inter-area routes.

Why the distractors are wrong:

• A (Type 1 + Type 2): Type 2 (Network) LSAs are generated only by the DR, not the BDR - the BDR takes over only if the DR fails.
• C (Type 1 + Type 4): Type 4 (ASBR Summary) LSAs are sent by ABRs to advertise the location of an ASBR; there is no ASBR role implied here for NGFW-1.
• D (Type 1 + Type 5): Type 5 (AS External) LSAs are sent by ASBRs to redistribute external routes into OSPF; NGFW-1 is not acting as an ASBR.

Memory tip: Think of it as two separate roles stacked - the BDR role (multi-access segment) determines it does not send Type 2s (that's the DR's job), while the ABR role (area boundary) determines it does send Type 3s. Every router always sends Type 1 - no exceptions.

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