Question 1mediummultiple choice
Full question →mediummultiple choiceObjective-mapped
Which statement best explains why BGP path-vector behavior is often presented as different from OSPF link-state 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
Because OSPF is an interior link-state protocol, while BGP is a path-vector protocol associated with interdomain routing.
This is correct because that is the main conceptual distinction between the two.
B
Distractor review
Because BGP is only for Layer 2 switching and OSPF is only for wireless networks.
This is wrong because both are Layer 3 routing protocols.
C
Distractor review
Because OSPF has no metrics and BGP always uses STP cost.
This is wrong because that misrepresents both protocols.
D
Distractor review
Because BGP and OSPF are both DHCP extensions.
This is wrong because neither protocol is a DHCP extension.
Common exam trap
Common exam trap: answer the scenario, not the keyword
A frequent exam trap is assuming BGP behaves like OSPF because both are routing protocols. Candidates may mistakenly think BGP uses link-state flooding or shortest path metrics like OSPF, leading to confusion about route selection and protocol scope. This misunderstanding can cause incorrect answers about how BGP handles routing information or why it is used between autonomous systems. Remember, BGP’s path-vector mechanism focuses on AS path attributes and policy, not topology maps or link costs, which is a key conceptual difference tested in CCNA.
Technical deep dive
How to think about this question
Border Gateway Protocol (BGP) is a path-vector routing protocol primarily used for interdomain routing between autonomous systems (ASes) on the internet. It exchanges reachability and path information, focusing on policy-based routing decisions rather than purely shortest path metrics. Open Shortest Path First (OSPF), in contrast, is an interior gateway protocol (IGP) that uses a link-state algorithm to build a complete topology map of a single routing domain, enabling routers to calculate the shortest path to each destination based on link costs. The fundamental difference in behavior arises because OSPF routers flood link-state advertisements (LSAs) to build a synchronized database of the network topology, allowing each router to independently compute the best path using Dijkstra’s algorithm. BGP, however, maintains path information as a vector of AS hops and uses attributes like AS path, local preference, and MED to select routes. This path-vector approach supports complex policy decisions and loop prevention across multiple autonomous systems, unlike OSPF’s metric-based shortest path selection within a single AS. A common exam trap is confusing BGP’s path-vector behavior with link-state or distance-vector protocols, leading to incorrect assumptions about metric calculation or route flooding. In practice, BGP does not flood topology changes like OSPF but advertises reachable prefixes with path attributes. Understanding this distinction helps avoid misinterpreting BGP as a simple metric-based protocol and clarifies why BGP is suited for interdomain routing while OSPF is optimized for intradomain routing.
KKey Concepts to Remember
- OSPF uses link-state advertisements to build a complete topology database within a single autonomous system for shortest path calculation.
- BGP exchanges path vectors containing AS path information to make routing decisions across multiple autonomous systems.
- BGP’s path-vector protocol supports policy-based routing and loop prevention by using attributes like AS path and local preference.
- OSPF calculates routes based on link costs using Dijkstra’s algorithm, focusing on intradomain routing efficiency.
- BGP does not flood topology changes but advertises reachable prefixes with path attributes to peers.
- OSPF operates as an interior gateway protocol, while BGP functions as an exterior gateway protocol for interdomain routing.
- Confusing BGP with link-state or distance-vector protocols leads to misunderstanding of routing behavior and scope.
- BGP’s design allows it to manage complex routing policies between autonomous systems, unlike OSPF’s focus on topology.
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.
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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 link-state advertisements to build a complete topology database within a single autonomous system for shortest path calculation.
What is the correct answer to this question?
The correct answer is: Because OSPF is an interior link-state protocol, while BGP is a path-vector protocol associated with interdomain routing. — The two protocols are presented differently because they approach route exchange and path reasoning in different ways. In practical terms, OSPF is an interior link-state protocol associated with topology awareness inside a routing domain, while BGP is associated with exchanging reachability and path information across autonomous-system boundaries. At CCNA level, the goal is to understand that these protocols serve different scopes and models of routing.
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.
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