CCDE 400-007: Which action can be performed to tune the device performance?

Table of Contents

Question
Answer
Explanation
Reference

Question

A BGP route reflector in the network is taking longer than expected to converge during large network changes. Troubleshooting shows that the router cannot handle all the TCP acknowledgements during route updates. Which action can be performed to tune the device performance?

A. Decrease the size of the small buffers.
B. Increase the size of the large buffers.
C. Increase the keepalive timers for each BGP neighbor.
D. Increase the size of the hold queue.

Answer

D. Increase the size of the hold queue.

Explanation

The correct answer to the question is D. Increase the size of the hold queue.

In the scenario where a BGP route reflector is taking longer than expected to converge during large network changes and the router is unable to handle all the TCP acknowledgments during route updates, increasing the size of the hold queue can be performed to tune the device performance. Here’s a comprehensive explanation:

Hold Queue: The hold queue is a buffer that holds BGP updates before they are processed by the router. It is used to temporarily store incoming BGP messages, allowing the router to handle them at its own pace. The hold queue size determines the number of BGP updates that can be buffered and processed concurrently.
Convergence Delay: During large network changes, such as route updates, the route reflector may receive a significant number of BGP updates from its peers. If the hold queue size is insufficient, the router may not be able to handle all the incoming updates immediately. This can result in delays in processing the updates and longer convergence times, as TCP acknowledgments are necessary for proper communication and synchronization between the BGP peers.
Increasing Hold Queue Size: By increasing the size of the hold queue, more BGP updates can be buffered, allowing the router to handle a higher volume of incoming updates. With a larger hold queue, the router can store a greater number of updates, reducing the likelihood of dropped or delayed TCP acknowledgments and improving overall convergence time.

The other options listed in the question are not appropriate actions to tune the device performance in this scenario:

Decreasing the size of the small buffers (A) is not recommended because it would further limit the router’s ability to handle BGP updates. This would likely exacerbate the convergence delay rather than resolve the issue.
Increasing the size of the large buffers (B) is not directly related to improving the handling of BGP updates and TCP acknowledgments. Large buffers may be useful in specific scenarios, but they do not directly address the performance issue caused by the hold queue size.
Increasing the keepalive timers for each BGP neighbor (C) would only affect the interval at which BGP keepalive messages are exchanged between the route reflector and its neighbors. While adjusting the keepalive timers may be beneficial in certain cases, it does not specifically address the performance issue related to handling TCP acknowledgments during route updates.

In summary, to improve the performance of a BGP route reflector during large network changes and ensure faster convergence, increasing the size of the hold queue is the recommended action. This allows the router to buffer and process a higher volume of BGP updates, reducing the impact of TCP acknowledgment issues and improving overall convergence time.

Reference

Cisco Certified Design Expert CCDE v3.0 400-007 certification exam practice question and answer (Q&A) dump with detail explanation and reference available free, helpful to pass the Cisco Certified Design Expert CCDE v3.0 400-007 exam and earn Cisco Certified Design Expert CCDE v3.0 400-007 certification.