hardMultiple ChoiceObjective-mapped
OSPF DR Identification from show ip ospf database
A network engineer issues the following command on Router R4:
R4# show ip ospf database
OSPF Router with ID (4.4.4.4) (Process ID 1)
Router Link States (Area 0)
Link ID ADV Router Age Seq# Checksum Link count
1.1.1.1 1.1.1.1 123 0x80000002 0x00A1B2 2 2.2.2.2 2.2.2.2 456 0x80000003 0x00B2C3 3 4.4.4.4 4.4.4.4 789 0x80000001 0x00C3D4 1
Net Link States (Area 0)
Link ID ADV Router Age Seq# Checksum
192.168.1.2 2.2.2.2 234 0x80000001 0x00D4E5
Based on this output, what can be concluded?
Quick Answer
The answer is that Router 2.2.2.2 is the Designated Router on the 192.168.1.0/24 segment. This is confirmed by the Net Link States entry in the `show ip ospf database` output, where the Link ID (192.168.1.2) is the DR’s interface IP address and the ADV Router (2.2.2.2) identifies the router that originated the Type 2 Network LSA—a function performed exclusively by the DR on a broadcast multiaccess network. On the ENCOR 350-401 exam, this question tests your ability to interpret OSPF LSDB entries and distinguish between Router Link States (Type 1) and Net Link States (Type 2), a common trap being that students confuse the Link ID with the DR’s Router ID rather than recognizing it as the DR’s interface IP. A reliable memory tip: the Link ID in a Type 2 LSA is always the DR’s interface IP on that segment, while the ADV Router is the DR’s Router ID—so when you see a Net Link State, the advertising router is your DR.
⚠ Common exam trap
Cisco often tests the misconception that the ADV Router in a Net Link State is the router that owns the IP address in the Link ID field, when in fact it is always the DR on that segment.
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
✓
Router 2.2.2.2 is the Designated Router on the segment 192.168.1.0/24.
The Net Link States entry shows the link ID 192.168.1.2 (the DR's interface IP) and ADV Router 2.2.2.2, which indicates that router 2.2.2.2 is the Designated Router (DR) on the 192.168.1.0/24 segment. In OSPF, only the DR originates the Type 2 (Network LSA) for a broadcast segment, so the advertising router in the Net Link States is always the DR.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Router 2.2.2.2 is the Designated Router on the segment 192.168.1.0/24.
Why this is correct
The Net Link State is originated by the DR, and the ADV Router is 2.2.2.2, so it is the DR.
- ✗
Router 1.1.1.1 has three OSPF-enabled interfaces.
Why it's wrong here
The link count for 1.1.1.1 is 2, not 3.
- ✗
Router 4.4.4.4 is the BDR on the segment.
Why it's wrong here
The BDR is not indicated in the database; the Net Link State is only from the DR.
- ✗
There are multiple broadcast segments in area 0.
Why it's wrong here
Only one Net Link State is listed, suggesting one broadcast segment.
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
2 more ways 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 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?
hard- ✓ A.R2 has a full OSPF adjacency with all neighbors on this segment.
- B.R2 is the Backup Designated Router on this segment.
- C.The OSPF cost to reach the network 192.168.1.0/24 is 20.
- D.R2 will send hello packets every 40 seconds.
Why A: 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.
Variation 2. 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.