Very Important DNS/Route 53 Interview Q & A
If you’re preparing for a DNS-related interview, here are some key questions to master!
1️⃣ What is DNS and why is it important?
✅ DNS (Domain Name System) resolves domain names (e.g., google.com) to IP addresses, enabling seamless internet communication.
2️⃣ Types of DNS Records?
✅ Common DNS records:
• A Record → Maps domain to IPv4.
• AAAA Record → Maps domain to IPv6.
• CNAME → Alias for another domain.
• MX → Mail server record.
• TXT → Stores arbitrary text data (SPF, DKIM).
3️⃣ What is the difference between Recursive & Iterative DNS Queries?
✅ Recursive Query: DNS server fully resolves the query by contacting other servers.
✅ Iterative Query: DNS server responds with a referral instead of resolving the query itself.
4️⃣ What are Primary, Secondary & Stub Zones?
✅ Primary Zone → Stores original writable DNS records.
✅ Secondary Zone → Read-only copy of Primary DNS zone.
✅ Stub Zone → Contains only Name Server (NS) records.
5️⃣ What is Forward & Reverse DNS Lookup?
✅ Forward Lookup → Resolves domain name to IP.
✅ Reverse Lookup → Resolves IP to domain name (PTR record).
🔹 DNS Server & Configuration
6️⃣ What is a DNS Resolver?
✅ A DNS Resolver is the first point of contact for a client making a DNS request. It caches results to improve resolution speed.
7️⃣ What is TTL (Time to Live) in DNS?
✅ TTL defines how long a DNS record is cached before it expires. Lower TTL means faster updates, but higher TTL reduces queries.
8️⃣ What is Split-Horizon DNS?
✅ Split-Horizon DNS serves different DNS responses based on internal vs. external network location, enhancing security & customization.
9️⃣ How do you flush the DNS cache on a Windows system?
✅ Run the following command:
ipconfig /flushdns
🔟 How do you test DNS resolution?
✅ Use:
nslookup example.com
Resolve-DnsName example.com
🔹 DNS Troubleshooting & Security
1️⃣1️⃣ How to troubleshoot DNS issues?
✅ Step-by-step approach:
• Check network connectivity (ping & tracert).
• Test name resolution (nslookup, Resolve-DnsName).
• Verify DNS server settings (ipconfig /all).
• Inspect DNS service status (Get-Service DNS).
• Flush DNS cache (ipconfig /flushdns).
1️⃣2️⃣ What is DNS Poisoning & How to Prevent It?
✅ DNS Poisoning (Cache Poisoning) injects false DNS data into a resolver’s cache, redirecting traffic.
✅ Prevention:
• Enable DNSSEC (Domain Name System Security Extensions).
• Use encrypted DNS (DoH, DoT).
• Restrict DNS cache TTL.
1️⃣3️⃣ What is DNSSEC?
✅ DNSSEC (DNS Security Extensions) adds cryptographic signatures to DNS records to prevent spoofing & tampering.
1️⃣4️⃣ How to change the DNS server on a Windows machine?
✅ Run:
Set-DnsClientServerAddress -InterfaceAlias "Ethernet" -ServerAddresses ("8.8.8.8","8.8.4.4")
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1April 24, 2025 1.9K 13
