mediumMultiple Choice
350-401 Practice Question: Interface GigabitEthernet0/0 ip address…
interface GigabitEthernet0/0 ip address 192.168.1.1 255.255.255.0 ip ospf network broadcast ip ospf priority 0
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router ospf 1 network 192.168.1.0 0.0.0.255 area 0
What is the effect of setting the OSPF priority to 0 on this interface?
⚠ Common exam trap
Cisco often tests the misconception that priority 0 means 'lowest priority' or 'least likely to become DR,' when in fact it means 'ineligible to become DR or BDR' — a binary disqualification, not a comparative value.
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
✓
The router will never become the DR or BDR on this segment.
Setting the OSPF priority to 0 on an interface prevents the router from participating in the Designated Router (DR) and Backup Designated Router (BDR) election process. This means the router will never become the DR or BDR on that broadcast segment, as per RFC 2328. It will instead remain a DROTHER and only form full adjacencies with the DR and BDR, not with other DROTHER routers.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
The router will never become the DR or BDR on this segment.
Why this is correct
In OSPF broadcast multiaccess networks, the DR/BDR election is governed by the interface priority field, which ranges from 0 to 255. Setting a priority of 0 explicitly marks the router as ineligible to participate in the election, so it can never be selected as the DR or BDR, regardless of its Router ID or any other factor. The router remains fully operational as a DROther and still establishes adjacencies with the DR and BDR.
- ✗
The router will have a higher chance of becoming the DR.
Why it's wrong here
The election logic selects the router with the highest priority value; increasing the priority above 0 would improve the odds of winning, but a priority of 0 eliminates eligibility entirely. With priority 0, the router is excluded from the candidate pool, so it has no chance of becoming the DR—not even a lower or equal chance, but literally zero. Therefore, the statement that it has a higher chance of becoming DR is false because eligibility is a prerequisite for election.
- ✗
The router will only form adjacencies with other routers that have priority 0.
Why it's wrong here
On an OSPF broadcast segment, every router must form a full adjacency with the DR and BDR, including routers with priority 0. Priority 0 routers become DROthers and do not establish full adjacencies with other DROthers—they only exchange Hello packets with them, not database descriptors. The statement is incorrect because priority 0 routers still form adjacencies with the DR and BDR, not exclusively with other priority 0 routers.
- ✗
The router will use a longer hello interval.
Why it's wrong here
The hello interval is a timer configured on the interface, typically 10 seconds on broadcast networks, and it controls how often Hello packets are sent. This timer is completely independent of the OSPF priority value; changing the priority to 0 has no effect on Hello or dead intervals. While mismatched Hello intervals can prevent adjacency formation, priority is used solely for DR/BDR election and does not influence any timer.
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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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.