Practical network guides
Network Troubleshooting Guides
Original guides for DNS records, SSL errors, headers, outages, email records, IP addressing, privacy, and Geo IP accuracy.
Use the tools with context
These guides explain what to check, how to read the result, and when to confirm findings with your DNS host, registrar, hosting provider, CDN, email provider, or security team. They are written for public diagnostics and authorized troubleshooting.
DNS and website troubleshooting
Understand A, AAAA, CNAME, MX, TXT, NS, TTL, and propagation.
DNSSlow DNS LookupsInvestigate resolver latency, TTL, CNAME chains, nameserver health, and local cache behavior.
DNSDNS Propagation vs TTLLearn why old DNS answers can appear after a change and how to plan safer migrations.
SSLSSL Certificate ErrorsCheck hostname coverage, expiry, certificate chains, CDN edges, and browser warnings.
WebsiteWebsite Downtime ChecklistA first-response sequence for DNS, SSL, headers, ports, and support evidence.
HeadersHTTP Security HeadersRead HSTS, CSP, X-Frame-Options, cache headers, redirects, and cookie signals.
Email, IP, and security guides
Review email DNS records before changing mail routing or sender authentication.
SSLCAA Records ExplainedUnderstand how CAA records can control certificate authority issuance.
IPPublic vs Private IP AddressesLearn private ranges, public routing, NAT, and why local addresses do not identify a website.
PrivacyVPN and Proxy IP ChecksUnderstand what your visible IP can reveal and what VPNs or proxies can change.
IPWhy Geo IP Can Be WrongUnderstand database lag, VPNs, CDNs, mobile networks, and routing estimates.
EmailReverse DNS for EmailLearn why PTR records matter for mail reputation and server identification.