Question 1hardmultiple choice
Full question →hardmultiple choiceObjective-mapped
Exhibit
R3 routing candidates for 10.50.0.0/16: via 10.0.23.2 cost 20 via 10.0.34.4 cost 20 Both learned as OSPF intra-area routes
Exhibit: R3 learns 10.50.0.0/16 by OSPF through two equal-cost paths. What will R3 do by default?
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
Install both routes and load balance
Equal-cost OSPF paths are installed by default.
B
Distractor review
Choose the route from the neighbor with the highest router ID only
That is not the standard OSPF path-selection rule for equal costs.
C
Distractor review
Install only one route because OSPF does not support ECMP
OSPF does support equal-cost multipath.
D
Distractor review
Prefer the path with the lower next-hop IP address
Next-hop IP address is not the deciding factor here.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is believing that OSPF will choose only one route when multiple equal-cost paths exist, often assuming it picks the route from the neighbor with the highest router ID or the path with the lowest next-hop IP address. This misconception leads to incorrect answers because OSPF’s path selection process installs all equal-cost routes by default. Misunderstanding this behavior can cause candidates to overlook OSPF’s load balancing capability and mistakenly select options that describe single-route preferences, which do not apply to equal-cost multipath scenarios.
Technical deep dive
How to think about this question
OSPF (Open Shortest Path First) is a link-state routing protocol that calculates the shortest path to each network using the Dijkstra algorithm. When a router learns multiple routes to the same destination with equal cost metrics, it can install multiple paths in its routing table. This capability allows OSPF to perform equal-cost multipath (ECMP) routing, which balances traffic across multiple links to optimize bandwidth and redundancy. By default, Cisco IOS routers running OSPF install all equal-cost routes up to a platform-specific maximum (commonly four or more) into the routing table. The router then load balances traffic across these paths, distributing packets evenly or based on per-flow hashing. This behavior improves network utilization and resilience without requiring manual configuration. A common exam trap is assuming OSPF selects a single route based on arbitrary criteria like the highest router ID or lowest next-hop IP address. These are not OSPF path selection rules for equal-cost routes. Instead, OSPF installs all equal-cost paths by default, and only when paths have unequal costs does it prefer the lowest cost route. Understanding this prevents misinterpretation of OSPF behavior and ensures accurate routing knowledge for the CCNA exam.
KKey Concepts to Remember
- OSPF uses the Dijkstra algorithm to calculate the shortest path to each destination network based on link-state information.
- When OSPF learns multiple equal-cost routes to the same destination, it installs all these routes into the routing table by default.
- OSPF supports equal-cost multipath (ECMP) routing, allowing load balancing across multiple paths with the same metric.
- Cisco routers have a default maximum number of equal-cost paths they can install, typically four or more, depending on the platform.
- OSPF does not select a single route based on the highest router ID or lowest next-hop IP address when multiple equal-cost paths exist.
- Load balancing in OSPF distributes traffic evenly or per-flow across all installed equal-cost routes to optimize bandwidth usage.
- Unequal-cost routes in OSPF result in the router preferring the path with the lowest cost metric, ignoring higher cost paths.
- Understanding OSPF ECMP behavior helps avoid common exam traps related to path selection and routing table installation.
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 uses the Dijkstra algorithm to calculate the shortest path to each destination network based on link-state information.
What is the correct answer to this question?
The correct answer is: Install both routes and load balance — When OSPF has equal-cost routes to the same destination, the router installs multiple paths and can load balance across them, assuming the platform supports the default maximum-paths value.
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.