hardMultiple Choice
OSPF DR Identification from show ip ospf database
A network engineer issues the following command on Router R2:
R2# show ip ospf interface GigabitEthernet0/0
GigabitEthernet0/0 is up, line protocol is up Internet Address 192.168.1.2/24, Area 0 Process ID 1, Router ID 2.2.2.2, Network Type BROADCAST, Cost: 10 Transmit Delay is 1 sec, State DR, Priority 1 Designated Router (ID) 2.2.2.2, Interface address 192.168.1.2 Backup Designated router (ID) 1.1.1.1, Interface address 192.168.1.1 Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 Hello due in 00:00:03 Index 1/1/1, flood queue length 0 Next 0x0(0)/0x0(0)/0x0(0) Last flood scan length is 1, maximum is 1 Last flood scan time is 0 msec, maximum is 0 msec
Neighbor Count is 2, Adjacent neighbor count is 2
Adjacent with neighbor 1.1.1.1 (Backup Designated Router) Adjacent with neighbor 3.3.3.3
Based on this output, what can be concluded?
⚠ Common exam trap
Cisco often tests the distinction between 'neighbor count' and 'adjacent neighbor count' — candidates may incorrectly assume that all neighbors are fully adjacent, but in broadcast networks, only the DR and BDR have full adjacencies with all routers, while other routers only have full adjacency with the DR and BDR.
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
✓
R2 has a full OSPF adjacency with all neighbors on this segment.
The output shows that R2 is the Designated Router (DR) on this broadcast segment, with two neighbors listed: 1.1.1.1 (BDR) and 3.3.3.3. The 'Adjacent neighbor count is 2' and both neighbors are listed as 'Adjacent with neighbor', confirming that R2 has formed full OSPF adjacencies with all neighbors on this segment. In OSPF broadcast networks, only the DR and BDR form full adjacencies with all routers, while non-DR/BDR routers only form full adjacencies with the DR and BDR.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
R2 has a full OSPF adjacency with all neighbors on this segment.
Why this is correct
The 'adjacent neighbor count' of 2 is equal to the total neighbor count, which in OSPF terminology means every discovered neighbor has reached the full state after completing database exchange. On a multi-access broadcast segment, only the DR and BDR form full adjacencies with all routers, so this equality confirms that R2 has fully synchronized its LSDB with both neighbors and no neighbor is stuck in two-way or exstart state.
- ✗
R2 is the Backup Designated Router on this segment.
Why it's wrong here
The show ip ospf interface output for R2 lists the interface state as DR, which stands for Designated Router, not BDR (Backup Designated Router). In the DR/BDR election, a router can only hold one of these roles on a given segment, and since R2 has been elected DR, it cannot simultaneously be the BDR. Moreover, the adjacent neighbor count matching the neighbor count is consistent with DR behavior, as the DR maintains full adjacencies with all neighbors.
- ✗
The OSPF cost to reach the network 192.168.1.0/24 is 20.
Why it's wrong here
The OSPF cost to reach 192.168.1.0/24 is displayed as 10 in the interface output, which is calculated using the reference bandwidth divided by the interface's configured bandwidth. A cost of 20 would imply a path with two hops of cost 10 each or an interface with half the bandwidth, but R2 is directly connected to this network, so the cost is simply the interface cost of 10. Thus, the statement incorrectly doubles the actual cost.
- ✗
R2 will send hello packets every 40 seconds.
Why it's wrong here
R2's hello interval for this OSPF interface is 10 seconds, as shown in the output, which is the default for broadcast multi-access networks. The 40-second value is actually the dead interval, which is the time R2 waits to declare a neighbor down after stopping to receive hello packets. Therefore, the statement confuses the hello interval with the dead interval, and R2 will send hellos every 10 seconds, not 40.
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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Same concept, more angles
1 more way this is tested on 350-401
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. A network engineer issues the following command on Router R8: R8# show ip ospf neighbor detail Neighbor 1.1.1.1, interface address 192.168.1.1 In the area 0 via interface GigabitEthernet0/0 Neighbor priority is 1, State is FULL, 6 state changes DR is 192.168.1.2, BDR is 192.168.1.1 Options is 0x42 (L LSR LSRR L LSR) Dead timer due in 00:00:34 Neighbor is up for 00:12:45 Index 1/1/1, retransmission queue length 0, number of retransmission 0 First 0x0(0)/0x0(0)/0x0(0) Next 0x0(0)/0x0(0)/0x0(0) Last retransmission scan length is 0, last retransmission scan time is 0 msec Based on this output, what can be concluded?
medium- A.Router 1.1.1.1 is the Designated Router on this segment.
- ✓ B.Router 1.1.1.1 is the Backup Designated Router.
- C.The neighbor state is 2WAY.
- D.The dead timer is 40 seconds.
Why B: The output shows 'BDR is 192.168.1.1', which is the interface address of neighbor 1.1.1.1. This directly indicates that router 1.1.1.1 is the Backup Designated Router on this segment. The neighbor state is FULL, confirming adjacency is fully established.
JA
Written by Johnson Ajibi, MSc IT Security
Senior Network & Security Engineer · founder of Courseiva
This 350-401 practice question is part of Courseiva's free Cisco certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the 350-401 exam.