Cisco CCNA (200-301)IP ConnectivityHard
Refer to the following router configuration: ``` router ospf 1 network 10.1.1.0 0.0.0.255 area 0 network 10.1.2.0 0.0.0.255 area 1 passive-interface GigabitEthernet0/0 ``` Which statement is true regarding the effect of the `passive-interface GigabitEthernet0/0` command?
- AGigabitEthernet0/0 will be completely excluded from OSPF routing and will not advertise its connected network.
- BThe 10.1.1.0/24 network will be advertised into OSPF, but OSPF packets will not be sent or received on GigabitEthernet0/0.
- COSPF routing updates will still be sent out GigabitEthernet0/0, but the interface will not form neighbor relationships.
- DGigabitEthernet0/0 will participate in OSPF routing, but it will not send or receive OSPF Hello packets.
Show answer & explanationAnswer & explanation
Correct answer: B. The 10.1.1.0/24 network will be advertised into OSPF, but OSPF packets will not be sent or received on GigabitEthernet0/0.
The `passive-interface` command prevents the sending and receiving of OSPF Hello packets on the specified interface, effectively preventing neighbor adjacencies. However, the network connected to that interface (if included in a 'network' command) will still be advertised into the OSPF domain.
Why the other options are wrong
- A. This is incorrect. The interface's connected network *is* advertised if a 'network' command covers it. Only OSPF protocol traffic is suppressed.
- C. This is incorrect. OSPF routing updates (including Hellos) are suppressed on a passive interface.
- D. This is the core effect; it prevents Hello packets. However, the interface's connected network will still be advertised into OSPF.
OSPF Passive Interface
A passive OSPF interface suppresses the sending and receiving of OSPF Hello packets, preventing neighbor adjacencies, but still advertises its connected network into the OSPF domain.
- Prevents OSPF Hellos on the interface.
- No OSPF neighbor relationships formed on passive interface.
- Connected network is still advertised into OSPF.
Memory trick: Passive means silent neighbor, but still tells everyone about its home.