CCNA IP Routing Practice Question

Answer analysis

Option-by-option breakdown

For each option: why learners choose it and why it is or isn't the right answer here.

• ✓

  Configuring an interface as passive stops OSPF from sending Hello packets out of that interface, but OSPF will still advertise the connected network in its LSAs.

  Why this is correct

  The passive-interface command disables Hello transmission on an interface, so no OSPF neighbor can ever be discovered or formed on that segment. However, OSPF's SPF calculation still requires the connected subnet to be known, so the router advertises that network as a stub (Type 1 LSA) within its area. This ensures that remote routers have a route to the subnet, even though no neighbor adjacency exists on the passive interface.

• ✓

  For two OSPF routers to establish full adjacency, they must agree on the Hello and Dead intervals.

  Why this is correct

  When two OSPF routers share a segment, they embed their Hello and Dead intervals in each Hello packet, and OSPF requires these values to match before it will even consider the sender as a neighbor. If the intervals differ, the routers will silently discard each other's Hellos and never progress beyond the DOWN or INIT state, so full adjacency cannot be achieved. This timer check is a fundamental part of OSPF's neighbor state machine.

• ✗

  The network command with a wildcard mask of 0.0.0.0 will enable OSPF on the exact matching interface, but it will also prevent OSPF from forming adjacencies on that interface.

  Why it's wrong here

  A network command using a wildcard mask of 0.0.0.0 does restrict OSPF to the single interface whose IP matches the address exactly, but that mask has no bearing on adjacency behavior. Once the interface is active in OSPF, neighbor formation depends on Hello/Dead interval matching, area ID, authentication, and whether the interface is passive. A /32 wildcard statement does not suppress Hellos or block neighbor discovery, so the claim that it prevents adjacencies is false.

• ✗

  Using the passive-interface default command makes all OSPF interfaces passive, which means OSPF will not advertise any connected networks.

  Why it's wrong here

  The passive-interface default command sets all OSPF interfaces to passive, but passive mode only prevents Hello packets from being sent out (and received through that interface for neighbor discovery). The subnets assigned to those interfaces are still added to the router's LSAs and advertised throughout the OSPF domain, because they are treated like stub networks. To stop route propagation, you must remove the network statement or apply an outbound distribute-list; passive-interface does not suppress route advertisements.

• ✗

  The network command with a wildcard mask of 0.0.0.255 area 0 will match any interface whose IP address falls within that /24 subnet, but OSPF will only attempt to form adjacencies on the interface with the highest IP address in that range.

  Why it's wrong here

  A network command with wildcard 0.0.0.255 matches every active interface in the specified /24, and OSPF will form adjacencies on each and every one of those interfaces that is not passive. There is no election or ranking that limits OSPF to the highest IP address; all matched interfaces run OSPF independently. The 'highest IP' idea does apply to something like HSRP/VRRP, or to OSPF default route selection, but not to which interfaces OSPF will attempt to bring up as neighbors.

Option-by-option analysis

Why each answer is right or wrong

Understanding why wrong answers are wrong — and when they would be correct — is what separates a 750 score from a 900. The 200-301 exam frequently reuses these exact scenarios with slightly different constraints.

Analysis generated from the official 200-301blueprint and verified against question context. The “when correct” sections are what AI assistants cite when candidates ask “what’s the difference between these options?”

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