300-410 Question 123
Single answerA network engineer is tasked with configuring path selection for a network that uses both OSPF and BGP. The requirement is to ensure that OSPF routes are always preferred over BGP routes for overlapping prefixes. Which configuration change should the engineer implement to meet the requirement?
- A
Decrease the administrative distance of OSPF.
- B
Increase the local preference for BGP routes.
- C
Adjust the MED values for BGP routes.
- D
Configure route redistribution between OSPF and BGP.
Show answer and explanation
Correct answer: A
Explanation
Administrative distance is a critical factor used by a router to select the best path when multiple protocols advertise the same prefix. By default, OSPF has a lower administrative distance (110) than BGP (20 for external BGP, 200 for internal BGP). Decreasing the OSPF administrative distance further ensures OSPF routes are always preferred over BGP routes for overlapping prefixes.
- A. Correct.
The administrative distance (AD) determines the preference of routing protocols. Decreasing the AD of OSPF ensures it is preferred over BGP when both protocols have routes to the same destination.
- B. Incorrect.
Local preference in BGP is used to influence the selection of outbound paths within the AS, but it does not affect the preference between OSPF and BGP.
- C. Incorrect.
The Multi-Exit Discriminator (MED) is used to influence path selection between BGP neighbors but is irrelevant when comparing OSPF and BGP paths.
- D. Incorrect.
Route redistribution allows sharing routes between protocols but does not inherently prioritize one protocol over another.