NetDebug Toolkit
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When something is broken right now and you need to know where.
Wi-Fi connected but no internet: how to find the real cause in four tests
Full bars, no internet, and a warning that tells you nothing. Ping the gateway, ping a public IP, resolve a name, fetch a page. The first test that fails is the answer, and each failure points at a completely different fix.
Read the postIs the website down, or just you? Four checks that settle it
A browser shows the same blank failure whether DNS broke, the connection was refused, the certificate expired or the server errored. Four checks separate them, and one more proves whether it is only you.
Read the post192.168.1.1 not working? How to actually reach your router
The address on the sticker is often wrong, and two of the most common causes are your VPN and your own browser forcing HTTPS. Work through this list before you reset anything and lose every setting.
Read the postHotel Wi-Fi login page not showing? How to force the captive portal
Portals fail more often now because they work by hijacking DNS and redirecting plain HTTP, which is exactly what modern browsers and encrypted DNS are built to prevent. Here is how to force the login page out.
Read the postSpeed, latency and call quality
Why fast connections still feel slow, and how to measure the numbers that matter.
High ping and lag: where the delay actually comes from
A faster plan almost never fixes lag, because lag is latency and latency is not bandwidth. Distance sets a floor you cannot beat, congestion causes the spikes, and a traceroute shows which one you are dealing with.
Read the postSlow internet when the speed test says it's fine
Speed tests answer one narrow question well and miss four others entirely: DNS delay, latency under load, jitter, and whether large packets survive the path. Test your LAN separately and the bottleneck usually appears immediately.
Read the postHow to test for packet loss, and what counts as too much
Speed tests are bad at finding loss, which is why calls freeze on connections that test perfectly. How to measure it properly, where to point the test, and why that scary looking middle hop in your traceroute is almost always lying.
Read the postVideo calls keep freezing? It is almost never your bandwidth
A call needs a few megabits, so capacity is never the problem. It needs consistency, and a late packet is discarded exactly like a lost one. Measure during the call, and check your upload rather than your download.
Read the postHow to test network speed between two computers
An internet speed test cannot measure your LAN. How to use iperf3 properly, what each link type should really deliver, and why a result of 94 Mbps points straight at a damaged cable rather than a slow network.
Read the postHow to read a traceroute, and what the asterisks really mean
A row of asterisks is not a fault and one slow hop is not a bottleneck. The TTL trick behind traceroute explains why, and there are only four patterns in the output that are genuinely worth acting on.
Read the postDNS and domains
Name resolution, record changes, mail authentication and registrations.
DNS server not responding: what it actually means and how to fix it
NXDOMAIN, SERVFAIL, REFUSED and a plain timeout are four different problems wearing the same costume. One comparison, resolving the same name against two resolvers, tells you whether to change a setting or go look at the domain.
Read the postDNS propagation: why your new record isn't live yet
Nothing propagates. Records change instantly at the authoritative server and slowly everywhere else, and the TTL tells you exactly how slowly. Plus the reason lowering the TTL after a change does absolutely nothing.
Read the postEmail going to spam? Check these three DNS records first
SPF, DKIM and DMARC decide whether your mail is trusted before anyone reads a word of it. What each record does, the mistakes that quietly break them, and the alignment rule that fails messages while every individual check passes.
Read the postWHOIS and RDAP: what you can still find out about a domain
Privacy rules removed the contact details and left the operational facts, which were always more useful. Expiry dates, status codes, nameservers, and why a domain registered eleven days ago deserves suspicion.
Read the postWeb servers and certificates
Reading the errors a server sends you, and the ones your browser invents.
502 Bad Gateway, 503 and 504: what each error actually means
All four are the server's fault, not your connection. 502 is a broken answer, 504 is no answer, 503 is usually a decision. Plus what Cloudflare's 520 to 526 codes actually mean when you see them.
Read the post"Your connection is not private": how to read SSL certificate errors
Each error code points at a different cause and a different person who can fix it. If several sites break at once, check your clock before anything else, and learn why a site can work in your browser and fail for everyone on a phone.
Read the postHome network and security
Devices, discovery, ports and the settings worth changing.
Who is on my Wi-Fi? How to list every device on your network
Thirty devices in an average home is normal now, and most people cannot name half of them. How to scan your subnet, identify what you find, and why an unfamiliar MAC address means much less than it used to.
Read the postAirPlay, Chromecast or printer not showing up on the network
A device that is reachable but invisible has a discovery problem, not a connection problem. Multicast does not cross subnets, client isolation kills it entirely, and on iOS one declined permission prompt makes a single app blind.
Read the postPort forwarding not working? Test every link in the chain
The rule is probably fine. A connection from the internet has to survive seven separate conditions, and one ten second comparison between your router's WAN address and your real public IP rules out the most common cause of all.
Read the postWake-on-LAN not working? Here is the whole chain to check
Magic packets are fire and forget, so nothing tells you which prerequisite failed. The broadcast address is usually the culprit, and Windows Fast Startup explains why waking from sleep works and waking from shutdown never does.
Read the postSubnet mask and CIDR explained, without the binary
What /24 really means, why you always lose two addresses, and the one subnet choice that quietly breaks VPNs for thousands of people. Subnetting explained as a question rather than a conversion table.
Read the postShould you disable UPnP? What the risk actually is
The advice online is split because the two sides describe different threats. What UPnP actually does, which warnings are real, and how to check what your router is genuinely exposing rather than guessing.
Read the postSome websites won't load on VPN: the MTU problem nobody mentions
Ping works, small pages load, large transfers hang forever on exactly the same sites every time. That deterministic pattern is an MTU black hole, and it is fixed with one number rather than a different VPN provider.
Read the postHomelab and self-hosting
Running services at home: exposure, certificates, DNS, containers and segmentation.
Self-hosting behind CGNAT: how to reach your homelab anyway
The forwarding rule was probably never the problem. One comparison tells you whether your ISP gave you an address inbound traffic can reach, and the five real options once you know it did not.
Read the postHTTPS for homelab services, without the certificate warnings
Real, publicly trusted certificates on services nobody outside your network can reach, with no open ports and no warnings on any device. Plus why a DNS zone on .local will never work reliably.
Read the postInternal DNS for a homelab: the traps nobody warns you about
Your own resolver gives you real names, split horizon and network wide blocking. It also makes you responsible for the most load bearing service on the network, and a second DNS entry is not the backup you think it is.
Read the postWhy your Docker container isn't reachable
Container running, logs clean, nothing can connect. The four network modes, the localhost binding trap, why containers cannot see your internal DNS, and why Docker quietly outranks your firewall.
Read the postVLANs for a homelab: what to segment, and what breaks
Creating the VLANs takes an evening. Finding everything that quietly depended on a flat network takes a fortnight. Here is that list up front, along with rules that make sense and how to test them.
Read the postWhy your NAS or server keeps dropping off the network
By the time you go and look, it is fine again. Catch what actually stops, then check the five settings responsible for nearly all of it, starting with a static IP sitting inside the DHCP pool.
Read the postMonitoring a homelab from outside it
Monitoring that runs inside your homelab cannot see expired certificates, stale DNS or a dropped tunnel. Five checks from a phone on cellular data can, and they chain into a single tap.
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