Which of the following descriptions of permanent multicast addresses is incorrect?

Question

Options

• AAll routers running the PIM multicast protocol listen on 224.0.0.13.
• BWith the OSPF protocol enabled, all routers listen on 224.0.0.5.
• CWhen the IGMP protocol is enabled, all hosts and routers in the network segment listen to 224.0.0.1.
• DAll routers running the OSPF protocol listen on 224.0.0.6.

• A
  3% (1)
• B
  13% (4)
• C
  9% (3)
• D
  75% (24)

Explanation

Option D is incorrect because 224.0.0.6 is reserved for OSPF Designated Routers (DR) and Backup Designated Routers (BDR) only - not all routers running OSPF. Only routers that have been elected to the DR or BDR role listen on that address, making the claim in D too broad.

Options A, B, and C are all accurate: 224.0.0.13 is the well-known "All PIM Routers" address used by every router participating in PIM (A is correct); 224.0.0.5 is the "All OSPF Routers" address that every OSPF-enabled router joins (B is correct); and 224.0.0.1 is the "All Hosts" group that every multicast-capable host and router on a segment listens to when IGMP is active (C is correct).

Memory tip: Think of the OSPF addresses as a ladder - 224.0.0.5 is for all OSPF routers (everyone on the team), while 224.0.0.6 is only for the elected leaders (DR and BDR). The higher number means a higher rank, not a wider audience.

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