DNS Deep Dive

Explore the anatomy of domain names from root to third level, learn labels and FQDN, and distinguish FQDN from URL, including domain syntax rules and common examples.

Explore how root servers serve as the first stop in DNS name resolution, issuing referrals to top-level domain servers and supporting 13 root servers A through M across global locations.

Discover how authority in the DNS protocol governs each domain segment through authoritative name servers, finalizing resolution by returning the IP address after root and TLD referrals.

Explore local name resolution using the hosts file, mapping IP addresses to hostnames without DNS. Learn its use cases, limitations, and best practices for manual, offline, or development scenarios.

Explore how DNS caching speeds name resolution by storing results, including negative caching, TTL-controlled entries, and the roles of client, resolver, and cache-only DNS servers.

Trace the dns name resolution workflow from an end user typing a domain to the final authoritative answer, covering recursive and iterative queries, resolvers, root name servers, referrals, and caching.

Explore reverse name resolution in dns using in-addr.arpa to map IPv4 addresses to domain names. Learn tools like ping -a, dig -x, and nslookup for troubleshooting and logging.

Learn to manipulate the name resolution order in Linux using the nsswitch.conf file, and control host resolution with the /etc/hosts file, multicast DNS, and DNS.

Choose a dns registrar by weighing pricing, registration and renewal fees, transfer policies, supported tlds, and add-on services, then consider privacy, ssl options, and reviews to optimize hosting separately.

Explore extensible provisioning protocol domain status codes, including client and server types, and their impact on registration, renewal, and transfers. Use whois lookups to inspect codes.

Explore how DNS data is stored in zones—forward and reverse lookup zones—and how resource records define name, type, class, ttl, rdlength, and rdata, including A and AAAA records.

Understand the start of authority (SOA) record, the zone’s primary name server, administrator email, serial number, and timing parameters (refresh, retry, expire, minimum) used for DNS caching and updates.

Explore how DNS uses pointer records for reverse name resolution, mapping ipv4 and ipv6 addresses to hostnames. Assess the reverse lookup zone structure and querying with nslookup and dig.

Learn how the cname record maps an alias to a canonical name, enabling subdomain to apex mappings, cross-tld redirects, and domain ownership validation, while restricting ip targets and avoiding chaining.

Explore the txt record as a flexible dns data storage for domain text. Query txt records with nslookup or dig and use them for domain ownership and email security.

Explore DNS architecture with a hands-on lab that builds a client, cache-only server and forwarder, a DNS resolver, and a high-availability pair of authoritative name servers for private lookups.

Configure dns high availability with a master-slave setup in Ubuntu, clone the master to create a slave, configure named.conf and zones, verify replication, and test failover.

Learn to set up a custom domain with your web hosting provider, configure A and CNAME DNS records, and understand DNS propagation up to 48 hours.

Explore DNS response codes (R codes) and learn how no error signals success while format error, server failure, NXDOMAIN, not implemented, or refused indicate issues for troubleshooting.

Explain dns header used in queries and responses, detailing transaction id, qr flag, opcodes, aa, tc, rd, ra, ad, cd, rcodes, and counts of questions, answers, authorities, and additional records.

Capture and analyze DNS traffic with tcpdump and Wireshark, choosing passive or active capture, set a client capture point, and observe recursive queries and iterative resolution through port 53 filters.

Construct DNS packets with Scapy and verify DNS server listens on port 53. Capture and analyze queries with Wireshark, adjust Transaction ID, source port, and Q type.

apply a structured troubleshooting approach to a cache-only dns server, identify a misconfigured dnssec setting in named.conf options, restart bind9, and restore name resolution.

Learn to troubleshoot DNS latency by inspecting ready-made traces in Wireshark, applying DNS time-delay filters, and using colorized highlights and buttons to identify slow responses and common root causes.

Understand the NX domain attack, a DNS based denial of service that floods resolvers with invalid records, degrading legitimate requests. Apply mitigations: restrict queries, block offending IPs, flush caches.