By the end of this lesson you will be able to
- Judge whether a problem is a weak Wi-Fi signal, a router fault or a provider fault.
- Restart a modem and router in the correct order and wait for them to settle.
- Explain what a firewall does and why you leave it switched on.
- Follow a decision tree to find where a home network is broken.
- Record what you found so that a provider's support team can help quickly.
Most home network faults are ordinary: a signal that is too weak in the back bedroom, a router that has been running for months and needs a restart, or a provider outage. A calm, ordered method lets you sort them without guessing. This lesson ends the networking module by putting the tools to work, using simulated situations so you can practise even if your own network is working perfectly.
Wi-Fi signal: is it the air?
Wi-Fi is radio, and radio gets weaker with distance and with obstacles. Walls (especially thick or metal-lined ones), floors, mirrors, water tanks and even fish tanks absorb the signal. The measure of how strong the signal is where you sit is signal strength, shown as bars beside the network name. Anything that disturbs the signal, such as neighbouring networks on the same channel or some microwave ovens, is called Interference.
The name your router announces is its SSID. Devices list nearby SSIDs so that you can choose one. Many routers broadcast two: a 2.4 GHz network that reaches further but is slower and more crowded, and a 5 GHz network that is faster but covers less distance and passes through walls less well.
Read this figure as text
A network diagram of a router in a hallway and devices in rooms at increasing distance with signal quality labels.
A router sits in a hallway in the middle. A laptop in the same room has excellent signal. A phone in the kitchen, one wall away, has good signal. A television in a bedroom, two walls away, has weak signal and often buffers. A printer in a shed at the far end of the garden has almost no signal and keeps dropping. The farther the device and the more walls between, the weaker the radio signal and the slower the connection.
- Move closer to the router and see whether the problem disappears. If so, it is the signal, not the router or the provider.
- Place the router high, in the open and near the middle of the home, not on the floor behind furniture or inside a cupboard.
- Try the other band. Choose the 5 GHz network for speed when you are near, and the 2.4 GHz network for range when you are far.
- Use a cable for a fixed device such as a desktop or television. A cable is not affected by walls.
- Add coverage with a mesh kit or an access point joined to the router by cable if the home is large.
Restarting a router properly
Routers are small computers that run for months without a break. Like any computer they can get into a muddle, and restarting clears it. A restart is also the standard first step any support team will ask for. Do it in the right order, because the router asks the modem for its settings when it starts.
Restart a home network in order
Step 1: Note the lights first
Look at the router and modem and write down which lights are on, off or blinking, and their colours. Take a photo if you like.
You should see: You have a record of the lights before the restart, useful for the provider's support.
Step 2: Switch off or unplug
Unplug the power from the router and from the modem, if they are separate. If they are one box, unplug that.
You should see: All lights go out.
Step 3: Wait
Wait about thirty seconds. This lets the parts discharge and lets the provider's equipment notice the break.
You should see: Nothing to see; just count.
Step 4: Power the modem first
Plug in the modem (or the single combined box) and wait two to five minutes until its lights settle, especially the one for the line or internet.
You should see: The line or internet light turns steady, not blinking.
Step 5: Then the router
If the router is a separate box, plug it in now and wait a further two minutes.
You should see: The Wi-Fi light turns on and your network name reappears on your devices.
Step 6: Check and record
Reconnect a device and open a website. Note whether the problem has gone.
You should see: The site opens. If not, keep your notes for the next step.
Firewalls: the gatekeeper
A Firewall is software or a device that watches network traffic and allows or blocks it according to rules. Think of a security guard at a building door: he lets in visitors who were expected and turns away those who were not. Your router has a simple one that blocks unrequested traffic coming in from the internet, which is also part of why NAT protects your private devices. Your computer has its own firewall too: Windows 11 includes Microsoft Defender Firewall, which is on by default.
- Connection arrivesFrom the network
- Firewall checks rulesAsked for? Which port?
- AllowedPasses to the program
- Not allowedDropped, often silently
Read this figure as text
A flow showing connection attempts passing through a firewall and being allowed or blocked.
Step 1: a connection attempt arrives at the firewall. Step 2: the firewall checks its rules, such as: is this a reply to something my computer asked for, and which program and port is it for. Step 3a: if a rule allows it, the traffic passes through to the program. Step 3b: if no rule allows it, the traffic is dropped, often without any message. Replies to your own requests are normally allowed; unrequested connections from outside are normally blocked.
Because a blocked connection is often dropped silently, a firewall can look like a fault: a ping gets no answer ('Request timed out'), or a program cannot be reached. That is one reason ping silence does not prove a computer is off. Leave your firewall switched on. Never turn it off 'just to test' on a computer that is connected to the internet; there is a safer way to test, which is the step-by-step method below.
Check that your firewall is on
Ubuntu 24.04 includes a firewall tool called UFW (Uncomplicated Firewall). On a fresh desktop it is installed but switched off, because a desktop with no services listening has little to protect. Its graphical front end, Firewall Configuration (gufw), is not installed by default and you do not need to install it now. Learn the idea; a later lesson on securing your system returns to this. Your router's firewall is still protecting you at the edge of your home.
On Windows 11
Step 1: Open Windows Security
Press the Start button, type Windows Security and press Enter.
You should see: The Windows Security window opens with a list of protection areas.
Step 2: Open Firewall and network protection
Click Firewall & network protection.
You should see: You see Domain network, Private network and Public network, each with a status.
Step 3: Read the status
Look at the network marked (active). It should say that Microsoft Defender Firewall is on.
You should see: A green tick or the word On. If it is off, a prompt with a Turn on button appears; use it.
A step-by-step diagnosis
Put everything together in a decision tree. Start at the top and answer each question truthfully. Every question points to one area; stop when you reach a result and do only that fix.
- Do other devices reach the internet?
- YesIs my device joined with a normal address (not 169.254)?
- YesCan I ping my gateway?
- YesDoes a name lookup answer?
- YesDo thisTry another site. Then check the firewall and browser add-ons.
- NoDo thisRestart the router and check which DNS server your device uses.
- NoDo thisMove closer to the router, try the other band, or use a cable.
- YesDoes a name lookup answer?
- NoDo thisTurn Wi-Fi off and on, rejoin, restart the device. If 169.254 stays, restart the router.
- YesCan I ping my gateway?
- NoAre the modem lights normal?
- YesDo thisRestart the router in order and test again.
- NoDo thisRestart modem then router in order. If lights stay wrong, contact the provider with your notes.
- YesIs my device joined with a normal address (not 169.254)?
Read this figure as text
A decision tree that starts by asking if other devices can reach the internet and ends in a fix for each branch.
Start: do other devices in the home reach the internet? If no (all devices fail): are the modem lights normal? If no, the modem or provider line is at fault: restart in order, then contact the provider with your notes about the lights. If yes, the router is the suspect: restart it in order and test again. If yes (other devices work, only mine fails): is my device joined to the Wi-Fi with a normal address, not 169.254? If no, rejoin the network, toggle Wi-Fi off and on, and restart this device; if it still has 169.254, restart the router. If yes, can I ping my gateway? If no, signal or link problem: move closer or use a cable. If yes, does a name lookup answer? If no, it is DNS: restart the router and check your DNS setting. If yes, the problem is the specific site or app: try another site, then check the firewall and any browser extensions.
When you must contact the provider, give them useful facts: the time the problem began, which lights are on the modem and router, whether all devices or only one fail, and what you have already tried. The notes you made during the restart steps are exactly that. Use only contact details printed on your own bill or the provider's official website, never a number from an unexpected message or pop-up.
Common mistakes
✖ Instead of: Changing several things at once, such as moving the router, changing settings and restarting everything.
✔ Do this: Change one thing, test, and note the result. Otherwise you will not know what fixed it or what made it worse.
✖ Instead of: Pressing the router's Reset hole as a 'restart'.
✔ Do this: Use the power plug or switch to restart. The Reset hole erases settings.
✖ Instead of: Phoning a support number from a pop-up that says your internet is infected.
✔ Do this: Use the number on your bill or the provider's official site. Real faults are not announced by pop-ups.
If something goes wrong
- After restarting, the modem's line light keeps blinking and never turns steady.
- Wait ten minutes, since some lines take a while to synchronise. Check that the line cable is firmly in. If it still blinks, contact the provider and give them your notes about the lights.
- The Wi-Fi name is missing from my devices after a restart.
- Wait two more minutes for the router to finish starting. If it never returns, the router may have reset to factory settings; look at the sticker on the router for the default name and ask the provider for help.
- Only one website will not open, but all others do.
- The fault is probably with that site. Try again later, try another browser, and only then look at the firewall or browser add-ons.
Key terms
- SSID
- The name a Wi-Fi network shows in the list of available networks.
- Signal strength
- How strong the radio signal from the router is where you are, often shown as bars.
- Interference
- Unwanted signals or obstacles that weaken or disturb a radio connection.
- Firewall
- A security feature that blocks unwanted network connections to or from your computer.
Practise it for real
Reading is not the same as being able to do it. Complete these on your own computer, then tick only what you have actually done. These ticks are your own honest record: nothing checks them for you.
Write a restart plan for your home
Find your modem and router (they may be one box). On paper, write which one is which, which lights should be on when everything is fine, where the power plug or switch is, and the order in which you would unplug and replug them. Do not restart anything unless you are happy to lose the connection for about ten minutes.
Challenge: diagnose three written cases
Use the decision tree to diagnose each case and name the single next action. Case A: Fatuma's phone and laptop both say Connected, no internet, the modem line light is off. Case B: only Joseph's laptop has no internet, its address is 169.254.18.2 and his phone works. Case C: all devices work, but Amina cannot reach one local printer from the bedroom, and ping to it fails sometimes with 40% loss.
Knowledge check
6 questions. You need 80% to pass. Mistakes here are part of learning, and you can retry as often as you like.
Summary
- Weak Wi-Fi is about distance and walls; test by moving closer, or use a cable.
- Restart the modem first, then the router, with a wait between; never use the Reset hole for a normal restart.
- A firewall allows or blocks traffic by rules; leave it on.
- Follow the decision tree from the outside in and change one thing at a time.
- Record the lights and symptoms before you phone anyone.
Checklist: can you do these?
Marking a lesson as read does not prove you can do it. Skills count as demonstrated when you pass the quiz (not yet) and complete the practical tasks (not yet).
Related lessons
References and further reading
Official sources for details that can change between versions.
- Wi-Fi problems and solutions in Windows (Microsoft Support)
- Networking, web, email and chat (Ubuntu Desktop Guide) (Ubuntu)
- Firewall and network protection in Windows Security (Microsoft Support)