Suddenly No Internet
If you suddenly see the message No internet connection, you should check all the key parameters of how your computer is connected to the Internet. Use this script for this.
The following chain exists between you and the website you need:
You - your browser - OS - NIC - [a connector-cable-connector | radio-ether-radio] - router - RJ45 - cable - ... routers domestic... - routers overseas ... - site server - site.
Check these links one by one to the end.
In order for you to receive information from the website, it must go through each of these nodes - as well as between them - without hindrance.
Make sure you really have no internet
To get started, check if it is true that you really do not have Internet? You may have an irresponsive browser that assures you there is no Internet. Before you believe there is no Internet - restart your browser and try to visit several popular websites. Maybe the internet will appear.
May be your NIC stopped responding.
Understand what you are dealing with.
If you are using Windows, then you know that Windows is extremely unreliable, and you are used to hangs and crashes (BSODs), which can occur in various ways at unexpected moments for a million different reasons.
The Mac operating system, like all Unix systems, is incomparably more reliable, but something in it may hang. At the same time, the rest will work properly - so you will not have any idea that some part of your computer has stopped working - until you notice that the computer behaves atypically. If you are actively using a computer, then this can happen to you every day - or even a couple of times a day.
So make it a rule: if you notice that something is not working as it should be, first of all -
Restart your computer
How does your computer gets the signal?
Via a LAN cable
If your computer is connected to the Internet via a wired connection, check if the cable is well plugged into the slot of the network card. Maybe you, for example, were cleaning your room and you had to move the computer away - you disconnected it, then you reconnected it - but not well enough. The RJ-45 cable jack snaps into the place with the well-audible click. Pull the jack out of the computer and plug in again, hear the click. Do the same in your router.
If via Wi-Fi: Check the router - is everything visually in place? Are 3 lights blinking as usual? Look at your computer - is Wi-Fi enabled? It happens that the Wi-Fi radio may unexpectedly be found off. The truth is that in this case you will most likely see the Wired Connection icon in the system tray instead of the Wi-Fi icon. Turn on Wi-Fi - maybe Internet will show up? If not, move on.
Does your router use standard factory firmware? Factory firmware is usually very unreliable. A good router made by a good company with a standard latest firmware can, for unknown reasons, break a connection several times a day.
Why does it happen? Because to create a good router is much easier than to use it effectively. Manufacturers connect the newest powerful processor with the newest powerful memory, put on top a cooling radiator, insert all this into a beautiful new case - and is the router ready? Not really.
Router, like a computer, has an Operating System. A router is a real computer, and it requires an operating system. Without an operating system its excellent hardware cannot work. And how will the old (developed in-house and adapted from the previous router) operating system work on a new hardware? This is a big question. The company will certainly expand and enhance it a little to fit the new improved hardware, but how it will actually work - developers have little idea. They can only speculate and hope for the best.
They hope everything will fit together and work well. Of course, the microcode needs to be tested and bug-fixed, but there is always no time for this - it is necessary to quickly release the new router to the market. And of course it must not be disclosed that the efficiency of the operating system using the new hardware is below 30%.
Of course, routers with DD-WRT, Open-WRT and Tomato firmware, based on the Linux kernel, are incomparably more reliable. They can work smoothly for years, but once in a life even they can hang. Who knows, maybe now is the very first and last time. So -
Reboot your router
Unplug the power cord, count 5 seconds, and plug it in again.
A router needs a minute to boot up its operating system and come into a working state.
Since we live in the 21st century and of course you are using a modern router, there is no doubt that IP addresses on your network are allocated by a router using the DHCP protocol. If a network crash occurred on your network and you had to reboot the router, make sure that the router has saved its settings — such as SSID (network name), password, router name, subnet address, and everything else. If those are saved - you are lucky, otherwise everything will have to be re-configured.