Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
Exhibit
Current state: R1 priority 1 - DR R2 priority 1 - BDR R3 priority changed from 1 to 200 after adjacency formed
Exhibit: On a broadcast multiaccess segment, R3 should become the OSPF DR, but it is staying DROTHER. Which explanation best fits OSPF behavior?
Answer choices
Why each option matters
Good practice is not just finding the correct option. The wrong answers often show the exact trap the exam wants you to fall into.
A
Best answer
DR election is nonpreemptive on broadcast networks
Changing priority later does not automatically replace the existing DR.
B
Distractor review
A router cannot become DR if it uses a loopback router ID
A loopback-based router ID is normal.
C
Distractor review
OSPF priority works only on point-to-point links
Priority matters on broadcast and NBMA segments, not point-to-point.
D
Distractor review
R3 must use area 1 to become DR
Area ID is unrelated to which router becomes DR on that segment.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A common exam trap is assuming that increasing a router's OSPF priority after the DR election will cause it to immediately become the new DR. Many candidates mistakenly believe OSPF DR election is preemptive and that the router with the highest priority always becomes DR instantly. However, OSPF DR election on broadcast networks is nonpreemptive, meaning the current DR remains until it fails or OSPF adjacency resets. This misunderstanding can lead to incorrect answers about why a router with a higher priority remains DROTHER, as in the case of R3 in the question.
Technical deep dive
How to think about this question
OSPF (Open Shortest Path First) is a link-state routing protocol that uses a designated router (DR) and backup designated router (BDR) election process on broadcast multiaccess networks to reduce the amount of OSPF routing update traffic. The DR acts as a central point for exchanging OSPF LSAs (Link State Advertisements) among routers on the same segment, improving efficiency and scalability. Routers on the segment elect the DR and BDR based primarily on OSPF priority values and router IDs. The OSPF DR election process on broadcast networks is nonpreemptive, meaning once a DR is elected, it remains the DR until it goes down or OSPF adjacency resets occur. Even if another router later has a higher priority or a higher router ID, it will not replace the current DR. This behavior prevents constant DR changes and network instability. The election uses priority as the first criterion, and if priorities tie, the highest router ID is used as a tiebreaker. A common exam trap is assuming that changing a router's OSPF priority dynamically will cause an immediate DR re-election. In reality, the existing DR remains in place until it fails or OSPF is reset on the segment. This nonpreemptive behavior means that a router like R3, despite having a higher priority, stays DROTHER if the current DR is still active. Understanding this helps network engineers predict OSPF behavior and avoid misconfigurations or false assumptions about DR roles during troubleshooting.
KKey Concepts to Remember
- OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks to optimize routing update exchanges.
- The OSPF DR election process uses router priority as the primary factor and router ID as a tiebreaker when priorities are equal.
- Once elected, the OSPF DR remains the DR until it goes down or OSPF adjacency resets, because the election process is nonpreemptive.
- Changing a router's OSPF priority after DR election does not trigger a new election or replace the current DR automatically.
- Routers with loopback-based router IDs can become DRs; the router ID type does not prevent DR election.
- OSPF priority values are relevant only on broadcast and NBMA networks, not on point-to-point links where DR election does not occur.
- The OSPF area ID does not influence which router becomes DR on a broadcast segment; DR election is local to the segment.
- Understanding OSPF DR election nonpreemptive behavior helps avoid misinterpretation of router roles during network troubleshooting.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Related practice questions
Related 200-301 practice-question pages
Use these pages to review the topic behind this question. This is how one missed question becomes focused revision.
CCNA subnetting practice questions
Practise IPv4 subnetting, CIDR, masks, host ranges and subnet selection.
CCNA OSPF practice questions
Practise OSPF neighbours, router IDs, metrics, areas and routing-table interpretation.
CCNA VLAN practice questions
Practise VLANs, access ports, trunks, allowed VLANs and switching scenarios.
CCNA STP practice questions
Practise spanning tree, root bridge election, port roles and STP troubleshooting.
CCNA EtherChannel practice questions
Practise LACP, PAgP, port-channel behaviour and bundle requirements.
CCNA ACL practice questions
Practise standard and extended ACLs, permit/deny logic and traffic filtering.
CCNA NAT practice questions
Practise static NAT, dynamic NAT, PAT and inside/outside address translation.
CCNA DHCP practice questions
Practise DHCP scopes, relay, leases and troubleshooting.
CCNA show ip route practice questions
Practise routing-table output, longest-prefix match, AD and route selection.
CCNA show interfaces trunk practice questions
Practise trunk verification and VLAN forwarding across switches.
CCNA wireless security practice questions
Practise WLAN security, authentication and wireless architecture concepts.
CCNA IPv6 practice questions
Practise IPv6 addressing, routes, neighbour discovery and common IPv6 exam traps.
More questions from this exam
Keep practising from the same exam bank, or move into a focused topic page if this question exposed a weak area.
Question 1
A router learns the same prefix from both OSPF and EIGRP. Which route is installed by default?
Question 2
A router shows this output: R1#show ip ospf neighbor Neighbor ID Pri State Dead Time Address Interface 10.1.1.2 1 FULL/DR 00:00:34 192.168.12.2 GigabitEthernet0/0 10.1.1.3 1 2WAY/DROTHER 00:00:39 192.168.12.3 GigabitEthernet0/0 Which statement is correct?
Question 3
What is the OSPF metric called?
Question 4
A non-root switch has two uplinks toward the root bridge. One path has a lower total STP cost than the other. What role will the lower-cost uplink have?
Question 5
A router interface applies this ACL inbound: 10 deny tcp any any eq 80 20 permit ip any any A user reports that web browsing to a server by IP address fails, but ping works. Which statement best explains the behavior?
Question 6
A router learns route 198.51.100.0/24 from OSPF with AD 110 and also has a static route to the same prefix configured with AD 150. Which route is installed?
FAQ
Questions learners often ask
What does this 200-301 question test?
OSPF elects a Designated Router (DR) and Backup Designated Router (BDR) on broadcast multiaccess networks to optimize routing update exchanges.
What is the correct answer to this question?
The correct answer is: DR election is nonpreemptive on broadcast networks — On broadcast networks, OSPF DR and BDR election is not preemptive. If a DR is already elected, giving another router a higher priority later does not force a new election unless the current DR goes down or OSPF is reset on the segment.
What should I do if I get this 200-301 question wrong?
Then try more questions from the same exam bank and focus on understanding why the wrong options are tempting.
Discussion
Loading comments…
Sign in to join the discussion.