300-445 Question 128
Select 2An enterprise network administrator has implemented a new DNS server to improve name resolution performance and redundancy. Despite proper configuration, users report intermittent failures in resolving domain names, especially during peak hours. Upon investigation, the administrator notices a high volume of queries to external DNS servers from the enterprise network. Which of the following actions should the administrator take to address the issue?
- A
Enable DNS caching on the enterprise DNS server to reduce external query traffic.
- B
Implement DNS rate limiting to prevent overloading of the DNS server.
- C
Configure split-horizon DNS to differentiate internal and external DNS queries.
- D
Increase the TTL value for frequently queried DNS records to reduce query frequency.
- E
Disable recursive DNS resolution on the enterprise DNS server to stop external lookups.
Show answer and explanation
Correct answers: A, D
Explanation
The issue described in the scenario points to high query traffic to external DNS servers, which can be mitigated by enabling DNS caching and increasing the TTL values for frequently queried records. These solutions reduce the need for repeated external lookups, alleviating the reported intermittent failures. Rate limiting and split-horizon DNS, while useful in other contexts, do not specifically address the problem in this case. Disabling recursive DNS resolution would negatively impact functionality for external lookups, making it an unsuitable solution.
- A. Correct.
Enabling DNS caching allows the server to store resolved queries locally, reducing the volume of external DNS queries and improving performance. This directly addresses the issue of high query traffic.
- B. Incorrect.
DNS rate limiting helps prevent abuse or overload caused by excessive queries but does not address the root cause of the issue described in the scenario.
- C. Incorrect.
Split-horizon DNS is useful for separating internal and external queries but is not directly relevant to the issue of high external query traffic in this specific scenario.
- D. Correct.
Increasing the TTL value for frequently queried DNS records helps reduce the number of DNS queries sent to external servers, effectively alleviating the issue.
- E. Incorrect.
Disabling recursive DNS resolution would prevent the DNS server from handling external lookups entirely, but this could lead to a loss of functionality for users needing external DNS resolution.