300-410 Question 120
Single answerA network engineer is troubleshooting routing issues on a network that runs both OSPF and BGP. The engineer notices that certain routes learned via OSPF are being preferred over BGP routes, even though the BGP routes have a lower administrative distance. Which configuration change can the engineer implement to ensure that BGP routes are preferred over OSPF routes?
- A
Manually increase the administrative distance of OSPF to a value greater than BGP
- B
Adjust the MED (Multi-Exit Discriminator) value for BGP routes
- C
Lower the OSPF cost on the interface
- D
Increase the weight attribute for BGP routes
Show answer and explanation
Correct answer: A
Explanation
When determining path preference, administrative distance is the primary factor used to decide between routes learned via different routing protocols. By default, BGP has a lower administrative distance (20 for EBGP and 200 for IBGP) compared to OSPF (110). If OSPF routes are being preferred, it indicates that a manual adjustment to the administrative distance is required to ensure BGP routes are prioritized.
- A. Correct.
Manually increasing the administrative distance of OSPF ensures that OSPF routes are deprioritized compared to BGP routes, as administrative distance is a primary factor in path selection.
- B. Incorrect.
Adjusting the MED value in BGP influences path selection for inbound traffic between BGP peers but does not affect the comparison between OSPF and BGP routes.
- C. Incorrect.
Lowering the OSPF cost changes intra-OSPF path selection but does not impact the preference between OSPF and BGP routes.
- D. Incorrect.
The weight attribute in BGP is a vendor-specific attribute that affects route selection within a single BGP router but does not influence comparisons with OSPF routes.