Quick Answer
The answer is that Router R1 is the Backup Designated Router (BDR). This is correct because the `show ip ospf neighbor` output explicitly lists the BDR as 10.1.1.1, which matches Router R1’s router ID, while the DR is 10.1.1.2. In OSPF multiaccess networks, the DR and BDR are elected based on the highest priority and router ID; the neighbor output reveals which router holds each role by displaying the DR and BDR IP addresses. On the Cisco CCNP ENARSI 300-410 exam, this type of question tests your ability to interpret OSPF neighbor states and identify router roles from command output, a common task in troubleshooting OSPF adjacencies. A frequent trap is confusing the neighbor’s router ID with the local router’s role—remember that the DR and BDR fields show the elected routers for the segment, not necessarily the neighbor you queried. Memory tip: “BDR is the one you’re looking at” — if the BDR field matches your local router ID, you are the backup.
This 300-410 practice question tests your understanding of ospf troubleshooting (v2/v3). Examine the command output carefully: the correct answer depends on what the output actually shows, not on general recall alone. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A network engineer runs the following command on Router R1:
R1# show ip ospf neighbor 10.1.1.2 Neighbor 10.1.1.2, interface address 192.168.12.2
In the area 0 via interface GigabitEthernet0/0
Neighbor priority is 1, State is FULL, 6 state changes
DR is 10.1.1.2, BDR is 10.1.1.1 Options is 0x12 (L L S R) Dead timer due in 00:00:36
Neighbor is up for 00:15:42
Index 1/1/1, retransmission queue length 0, number of retransmission 0 First 0x0(0)/0x0(0) Next 0x0(0)/0x0(0) Last retransmission scan length is 0, time is 0 msec Last retransmission scan time is 0 msec
Based on this output, what is the role of Router R1 on this segment?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "first"
Why it matters: Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
Router R1 is the Designated Router.
Why wrong: The DR is listed as 10.1.1.2, not 10.1.1.1.
Router R1 is the Backup Designated Router.
The BDR is 10.1.1.1, which is R1's router ID.
Router R1 is a DROTHER router.
Why wrong: The state is FULL, and BDR is specified, so R1 is not a DROTHER.
Router R1 has no special role on this segment.
Why wrong: It is the BDR, which is a specific role.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Router R1 is the Backup Designated Router.
The output shows that the BDR is 10.1.1.1, which is Router R1's router ID. Therefore, R1 is the Backup Designated Router. The DR is 10.1.1.2.
Key principle: OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Router R1 is the Designated Router.
Why it's wrong here
The DR is listed as 10.1.1.2, not 10.1.1.1.
Router R1 is the Backup Designated Router.
Router R1 is a DROTHER router.
Why it's wrong here
The state is FULL, and BDR is specified, so R1 is not a DROTHER.
Router R1 has no special role on this segment.
Why it's wrong here
It is the BDR, which is a specific role.
Common exam traps
OSPF neighbour formation depends on matching areas, timers, network type, authentication and passive-interface behaviour. Do not choose an answer only because the devices can ping.
Detailed technical explanation
OSPF questions usually test the details that control adjacency and route selection. Read the neighbour state, area, router ID and interface configuration before deciding what is wrong.
Key takeaway
OSPF neighbour adjacency depends on matching area, hello/dead timers, network type, and authentication — IP reachability alone is not enough.
Real-world example
A network engineer at a university connects two campus buildings via a fibre link. Both routers run OSPF, but no adjacency forms — even though both routers can ping each other. The engineer finds one router is in area 0 and the other in area 1. OSPF adjacency requires matching area numbers, hello/dead timers, and network type. IP reachability alone is not enough.
What to study next
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
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FAQ
OSPF Troubleshooting (v2/v3) — This question tests OSPF Troubleshooting (v2/v3) — OSPF neighbours must agree on key parameters..
The correct answer is: Router R1 is the Backup Designated Router. — The output shows that the BDR is 10.1.1.1, which is Router R1's router ID. Therefore, R1 is the Backup Designated Router. The DR is 10.1.1.2.
Review OSPF neighbour requirements — matching area type, hello and dead timers, network type, stub flags, and authentication. Study show ip ospf neighbor states (INIT, 2-WAY, FULL). Then practise related 300-410 OSPF questions on adjacency and route selection.
Yes — watch for: "first". Order matters here. You are being tested on which action comes before the others — not which action is generally useful.
OSPF neighbours must agree on key parameters.
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Same concept, more angles
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 runs the following command on Router R1: R1# show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DROTHER 00:00:35 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 FULL/DR 00:00:32 192.168.13.3 GigabitEthernet0/1 Based on this output, which statement is correct?
mediumWhy B: The output shows two OSPF neighbors. The neighbor with state FULL/DROTHER indicates it is not the DR or BDR on that segment. The neighbor with state FULL/DR is the designated router. The dead times are within normal range, indicating the adjacency is stable.
Variation 2. A network engineer runs the following command on Router R1: R1# show ip ospf interface GigabitEthernet0/0 GigabitEthernet0/0 is up, line protocol is up Internet Address 192.168.12.1/24, Area 0 Process ID 1, Router ID 10.1.1.1, Network Type BROADCAST, Cost: 10 Transmit Delay is 1 sec, State BDR, Priority 1 Designated Router (ID) 10.1.1.2, Interface address 192.168.12.2 Backup Designated router (ID) 10.1.1.1, Interface address 192.168.12.1 Timer intervals configured, Hello 10, Dead 40, Wait 40, Retransmit 5 oob-resync timeout 40 Hello due in 00:00:03 Neighbor Count is 1, Adjacent neighbor count is 1 Adjacent with neighbor 10.1.1.2 (Designated Router) Suppress hello for 0 neighbor(s) Based on this output, which statement is correct?
mediumWhy C: The interface is in state BDR, meaning Router R1 is the backup designated router. The DR is 10.1.1.2. The output shows one neighbor, which is the DR, and the adjacency is full.
Last reviewed: Jun 18, 2026
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