2026-10-18 · IPv4Scanner · 6 min read
How NAT lets a whole household share one IPv4 address, why it blocks incoming connections, and what port forwarding, UPnP and CGNAT actually change.
2026-10-17 · IPv4Scanner · 7 min read
A MAC address gets a frame across your local network; an IP address gets a packet across the internet. How they work together, how to find both, and randomised MACs.
2026-10-16 · IPv4Scanner · 6 min read
The three RFC 1918 private ranges, plus 100.64.0.0/10 CGNAT space, 169.254 link-local, and the IPv6 equivalents, with what each one tells you when you see it.
2026-10-15 · IPv4Scanner · 7 min read
Why your IPv6 address changes every day or so, how temporary privacy addresses work under RFC 8981, and how to see which address your device actually uses.
2026-10-14 · IPv4Scanner · 6 min read
How carrier-grade NAT puts many customers behind one public IPv4 address, how to tell if your ISP uses it, and what it breaks, from CAPTCHAs to hosting.
2026-10-13 · IPv4Scanner · 6 min read
What an Autonomous System Number is, how networks use BGP and ASNs to route traffic, how to look up the ASN behind any IP, and what the number tells you.
2026-10-12 · IPv4Scanner · 6 min read
A practical checklist for keeping a business domain healthy: registration and renewal, DNS, TLS certificates, HTTPS and email authentication, and how often to check.
2026-10-11 · IPv4Scanner · 6 min read
How to find a domain's registration date with WHOIS or RDAP, what that date does and doesn't prove, and where domain age matters: phishing, due diligence and email.
2026-10-10 · IPv4Scanner · 6 min read
The stages a domain goes through after it expires, from auto-renew grace to the 30-day redemption period and the 5-day pending delete, and how ccTLDs differ.
2026-10-09 · IPv4Scanner · 6 min read
Why SPF fails with PermError after 10 DNS lookups, which mechanisms count toward the limit, how to count yours with dig, and safe ways to get back under it.
2026-10-08 · IPv4Scanner · 6 min read
What's inside a DMARC aggregate report, what each XML field means, and how to sort sources into yours, forwarders and spoofers before tightening your policy.
2026-10-07 · IPv4Scanner · 6 min read
How MX records route email, what the priority numbers mean, what happens when there's no MX at all, and the common setup mistakes that quietly lose your mail.
2026-10-06 · IPv4Scanner · 6 min read
Why DNS forbids a CNAME on a bare domain like example.com, what breaks when a provider lets you do it anyway, and how ALIAS, flattening and redirects get around it.
2026-10-05 · IPv4Scanner · 7 min read
How Let's Encrypt issues free certificates, how ACME challenges prove domain control, the 2026 to 2028 lifetime changes, and how to make renewal truly automatic.
2026-10-04 · IPv4Scanner · 6 min read
What each field in an SSL/TLS certificate means, from Subject Alternative Names to the issuer, validity dates and chain, with openssl commands to read them yourself.
2026-10-03 · IPv4Scanner · 6 min read
DoH and DoT both encrypt DNS lookups. What each one hides, what it leaves exposed, how they differ on ports and blocking, and how to test that yours works.
2026-10-03 · IPv4Scanner · 6 min read
How to read a DNS TTL with dig, which values to use for A, MX, TXT and NS records, the TTLs you can't control, and a timeline for lowering TTL before a move.
2026-10-03 · IPv4Scanner · 6 min read
A step-by-step plan for moving a site to a new host with no outage: lower TTLs, copy files and database, test before DNS changes, get SSL ready and cut over safely.
2026-10-03 · IPv4Scanner · 6 min read
What an expired SSL certificate looks like in Chrome, Firefox and Safari, how to confirm the cause with openssl, fix it fast, and stop renewals failing again.
2026-10-02 · IPv4Scanner · 6 min read
How to change your DNS server on Windows, macOS, Android, iPhone and your router, what switching really improves, what it can break, and how to check it worked.
2026-10-01 · IPv4Scanner · 6 min read
What DNS_PROBE_FINISHED_NXDOMAIN means, how to tell if the problem is your device or the domain itself, and the fixes that work for visitors and site owners.
2026-09-30 · IPv4Scanner · 6 min read
How reverse DNS and PTR records work, who controls them, why Gmail and other mail servers reject mail without one, and how to check and fix yours.
2026-09-26 · IPv4Scanner · 5 min read
What each common DNS record type does, when to use a CNAME versus an A record, and the mistakes that quietly break a domain.
2026-09-26 · IPv4Scanner · 4 min read
What open, closed and filtered ports actually mean, how to check a port from outside your network, and which ports you never want exposed.
2026-09-26 · IPv4Scanner · 5 min read
Anyone can put GPTBot in a user-agent string. Here's how to check an AI crawler is genuine using published IP ranges and forward-confirmed reverse DNS.
2026-09-26 · IPv4Scanner · 5 min read
Which AI bots to allow and which to block, the exact robots.txt tokens for GPTBot, ClaudeBot and the rest, and why blocking the wrong one removes you from AI search.
2026-09-25 · IPv4Scanner · 4 min read
What ping actually measures, what counts as good for gaming and video calls, and why a low ping matters more than a big download number.
2026-09-24 · IPv4Scanner · 4 min read
What each line of a traceroute means, why gaps and high hops usually aren't the problem, and how to actually tell where a slow connection breaks.
2026-09-23 · IPv4Scanner · 4 min read
The real reasons legitimate email lands in spam, from authentication to reputation to blacklists, and a practical order to fix them in.
2026-09-22 · IPv4Scanner · 5 min read
What SPF, DKIM and DMARC actually do, how the three fit together to stop spoofing, and the order to set them up without breaking your own mail.
2026-09-21 · IPv4Scanner · 4 min read
Where IP location data comes from, how accurate it actually is by country and connection type, and why it puts some people in the middle of a field.
2026-09-21 · IPv4Scanner · 5 min read
How DNS blacklists work, why your address ended up on one, and the realistic steps to get removed and stay off.
2026-09-20 · IPv4Scanner · 4 min read
What the slash in 192.168.1.0/24 means, how to work out network and broadcast addresses, and how to split a network without the maths hurting.
2026-09-19 · IPv4Scanner · 4 min read
How much bandwidth each activity actually needs, why upload and latency matter more than the headline number, and how to stop overpaying.
2026-09-19 · IPv4Scanner · 5 min read
Why two speed tests minutes apart disagree, which variables actually matter, and how to run a test you can draw conclusions from.
2026-09-18 · IPv4Scanner · 4 min read
How to read a WHOIS record, which dates and statuses actually matter, and why most contact details are now redacted.
2026-09-18 · IPv4Scanner · 4 min read
What domain privacy actually hides, what GDPR already redacts for free, and when paying for privacy protection is worth it.
2026-09-17 · IPv4Scanner · 4 min read
Find your router's IP address on Windows, macOS, Linux, iPhone and Android, plus what to do when the usual addresses don't work.
2026-09-16 · IPv4Scanner · 5 min read
What a VPN, a proxy and Tor actually do to your traffic, what each one hides and from whom, and which is the right tool for the problem you have.
2026-09-16 · IPv4Scanner · 4 min read
The real difference between static and dynamic IP addresses, when paying for a static one is worth it, and the workarounds that make it unnecessary.
2026-09-15 · IPv4Scanner · 5 min read
What an IP address actually is, why yours changes, the difference between public and private addresses, and what a website can really tell about you from it.
2026-09-15 · IPv4Scanner · 5 min read
Why IPv6 exists, how it differs from IPv4 beyond address length, why adoption took decades, and what it means for you in practice.
2026-09-14 · IPv4Scanner · 6 min read
Why DNS changes don't appear instantly, what TTL actually controls, and how to check propagation from around the world without waiting 48 hours.