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Practical, no-fluff explanations of the network protocols and records you actually have to debug. Each guide pairs with a tool on this site so you can run the lookup yourself.
DNS
DNS Records Explained
A practical guide to A, AAAA, CNAME, MX, TXT, NS, CAA, and other DNS record types.
7 min read · Updated 2026-06-15MX Records And Email Routing
How mail exchanger records decide where domain email is delivered and how to troubleshoot them.
6 min read · Updated 2026-05-06SPF, DKIM, And DMARC Explained
A domain owner's guide to the DNS records that help receivers trust email.
8 min read · Updated 2026-06-02TLS
TLS Certificate Expiration And Troubleshooting
How to inspect certificate dates, names, issuers, and trust problems before users see errors.
7 min read · Updated 2026-05-06DNS
NXDOMAIN vs SERVFAIL: What DNS Errors Actually Mean
What is NXDOMAIN and what is SERVFAIL? NXDOMAIN means the DNS name does not exist; SERVFAIL means the resolver could not get a clean answer. Two different DNS errors, two different fixes.
5 min read · Updated 2026-06-18RDAP
RDAP vs WHOIS: What Replaced WHOIS And Why
WHOIS is a 40-year-old plaintext protocol. RDAP returns the same data as structured JSON over HTTPS. Here's what each one is and when to use which.
6 min read · Updated 2026-06-18DNS
DNS TTL Explained: What Is TTL in DNS?
DNS TTL (time to live) tells resolvers how long to cache a record. Learn what TTL means in DNS, sensible default TTL values, and how to set TTL before a migration.
5 min read · Updated 2026-06-18DNS
What Is A CAA Record?
A CAA record tells the world's CAs which of them are allowed to issue certificates for your domain. Cheap insurance against mis-issuance.
5 min read · Updated 2026-05-14DNS
nslookup vs dig: Which DNS Tool Should You Use?
nslookup vs dig — what is the difference? nslookup is the older, simpler DNS lookup tool; dig shows the full DNS response for troubleshooting. Here's when to use each.
6 min read · Updated 2026-06-18Network
Subnetting For Beginners: CIDR, Masks, And /24 Math
Subnetting is just counting in binary. This guide walks through what /24 means, how CIDR works, and why /30 is the smallest useful IPv4 subnet.
8 min read · Updated 2026-05-14