mediumMultiple Choice
300-410 Practice Question: Examine this OSPF configuration on router R5:…
Examine this OSPF configuration on router R5:
router ospf 1 network 10.0.0.0 0.255.255.255 area 0 passive-interface default no passive-interface GigabitEthernet0/0
What is the effect of the passive-interface default command?
⚠ Common exam trap
The trap here is assuming that `passive-interface default` makes all interfaces passive without exception, ignoring the subsequent `no passive-interface` override; candidates must remember that the `no` form explicitly re-enables OSPF on the specified interface.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
All interfaces except GigabitEthernet0/0 will be passive; GigabitEthernet0/0 will send and receive OSPF hellos.
The `passive-interface default` command sets all OSPF-enabled interfaces to passive mode by default, meaning they will not send or receive OSPF hello packets. The subsequent `no passive-interface GigabitEthernet0/0` explicitly overrides this default for that interface, making it active. Therefore, all interfaces except GigabitEthernet0/0 become passive, while GigabitEthernet0/0 participates fully in OSPF by sending and receiving hellos.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
All interfaces except GigabitEthernet0/0 will be passive; GigabitEthernet0/0 will send and receive OSPF hellos.
Why this is correct
The passive-interface default command sets every interface passive, suppressing OSPF hello transmission and reception. The no passive-interface GigabitEthernet0/0 exception restores normal adjacency formation on that interface, letting it send and receive hellos while all others remain silent.
- ✗
All interfaces are passive, including GigabitEthernet0/0, because the no passive-interface command is ignored.
Why it's wrong here
The no passive-interface GigabitEthernet0/0 line explicitly exempts that interface, so it remains active and forms adjacencies; the command is honoured, not ignored. Passive-interface default would be correct if every interface, including GigabitEthernet0/0, needed to suppress OSPF hellos.
- ✗
Only interfaces with network statements will be affected; other interfaces remain active.
Why it's wrong here
Passive-interface default suppresses OSPF adjacencies on every interface, not merely those matched by network statements; the no passive-interface GigabitEthernet0/0 line proves this by re-enabling one interface explicitly. It is tempting because network statements do govern which interfaces run OSPF, but the default command flips the global behaviour for all of them.
- ✗
The configuration is invalid because passive-interface default cannot be used with OSPF.
Why it's wrong here
The command is valid OSPF syntax on Cisco IOS, so the configuration loads and runs; it sets all interfaces passive, then GigabitEthernet0/0 is re-enabled. It is tempting because passive-interface default is unfamiliar and looks like a syntax clash with network statements, but no such conflict exists in OSPF.
Visual reference
Quick reference
Routing Protocol Comparison
| Protocol | Metric | Max Hops | Algorithm | Type |
|---|---|---|---|---|
| RIP v2 | Hop count | 15 | Bellman-Ford | Distance vector |
| OSPF | Cost (bandwidth) | Unlimited | Dijkstra (SPF) | Link state |
| EIGRP | Composite metric | Unlimited | DUAL | Hybrid |
| IS-IS | Cost | Unlimited | Dijkstra | Link state |
| BGP | Policy / attributes | Unlimited | Path vector | Path vector |
RIP's 15-hop limit makes it unsuitable for large networks. OSPF and EIGRP dominate modern enterprise deployments.
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Written and reviewed by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
Last reviewed September 2026 · checked against the official Cisco exam blueprint
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