Which of the following description of the permanent multicast address is wrong?

Question

Options

• AAll routers running OSPF protocol listen on 224.0.0.5
• BAll routers on the router's network segment listen to 224.0.0.1
• CAll routers listen on 224.0.0.2
• DAll routers running the PIM protocol listen on 224.0.0.100

• A
  8% (4)
• B
  4% (2)
• C
  14% (7)
• D
  75% (38)

Explanation

Option D is wrong because PIM (Protocol Independent Multicast) routers use 224.0.0.13 as their reserved multicast address, not 224.0.0.100 - that address doesn't correspond to any IANA-assigned permanent multicast group.

The other options describe real, valid assignments: A is correct because OSPF uses 224.0.0.5 (AllSPFRouters) for hello and update traffic; B is correct because 224.0.0.1 is the "All Hosts" group, which all IP-capable devices including routers join by default; C is correct because 224.0.0.2 is the "All Routers" group that every router must listen on regardless of routing protocol.

Memory tip: Learn the low-numbered reserved multicast addresses in order - .1 = All Hosts, .2 = All Routers, .5 = OSPF routers, .6 = OSPF Designated Routers, .13 = PIM routers. Any answer citing a three-digit last octet (like .100) for a well-known protocol should be an immediate red flag.

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