What to Check Before Calling Your ISP

When your internet connection becomes slow, unstable or completely unavailable, it is tempting to contact your internet service provider immediately.

Sometimes that is exactly the right move. A fault may exist on the broadband line, in the provider’s local network or with the equipment supplied to your property.

However, many apparent ISP problems are caused by something inside the home or office, such as:

• Weak Wi-Fi coverage
• A damaged Ethernet cable
• A frozen router
• A device downloading a large update
• A VPN connection
• A faulty network switch
• An expired service account
• A problem affecting only one website or application

Running a few structured checks before calling can save time, prevent unnecessary engineer visits and give the support team better evidence to investigate the fault.

The aim is not to perform advanced engineering work yourself. It is to establish where the problem begins.

First, Define the Problem Clearly

“Internet not working” can describe several different faults.

Before troubleshooting, decide which of these best matches the situation:

• No devices can connect to the internet.
• Devices connect to Wi-Fi but websites do not load.
• Only one device is affected.
• Only Wi-Fi devices are affected.
• Wired devices are affected too.
• The internet is slow rather than completely offline.
• The connection drops at certain times.
• Uploads are slow but downloads are normal.
• One application or website is affected.
• The router regularly restarts.
• The connection fails only during video calls or gaming.

This distinction is important because each pattern points towards a different area.

Check Whether the Problem Affects Every Device

Test the connection on at least two devices.

For example:

• A phone
• A laptop
• A television
• A desktop computer
• A tablet

When only one device has a problem, the broadband service itself is less likely to be at fault.

The affected device may have:

• Incorrect network settings
• A damaged Wi-Fi profile
• A VPN problem
• Outdated drivers
• Security software blocking access
• A browser fault
• Malware
• A hardware problem

When several unrelated devices fail at the same time, the router, local network or ISP becomes a stronger suspect.

Check Whether Wi-Fi Is the Only Problem

A broadband service can be working normally while the Wi-Fi connection is poor.

Where possible, connect a laptop or desktop directly to the router using Ethernet.

Then test the internet again.

If Ethernet works but Wi-Fi does not

The likely cause is inside the wireless network.

Possible issues include:

• Poor router placement
• Interference
• Weak coverage
• A failed access point
• An overloaded mesh system
• A device connected to the wrong Wi-Fi band
• A problem with the client’s wireless adapter

If Ethernet and Wi-Fi both fail

The issue may involve:

• The broadband line
• The router
• The provider network
• A general outage
• DNS
• Account suspension
• A wider local-network fault

This comparison is one of the most valuable checks you can perform before contacting the provider.

Look at the Router Lights

Router lights provide a quick indication of which part of the connection may have failed.

Common indicators include:

• Power
• Broadband, DSL or fibre
• Internet
• Wi-Fi
• Ethernet
• Phone
• Alarm or fault

The exact colours and symbols vary by provider.

Power light off

Check:

• The power socket
• The power switch
• The adapter
• Extension leads
• Whether another device works in the same socket

Use only the correct power adapter for the router.

Broadband or DSL light flashing

This may mean the router is trying to synchronise with the provider’s line.

Possible causes include:

• A line fault
• Loose cabling
• A damaged filter
• Provider maintenance
• A router or modem fault

Internet light off or red

The router may have a physical broadband connection but no working internet session.

Possible causes include:

• Authentication failure
• Provider outage
• Account issue
• Router configuration problem
• Failed WAN connection

Wi-Fi light off

The internet may still work over Ethernet even though the router’s wireless radio is disabled or faulty.

Take a photograph of the router lights before restarting it. This can be useful when speaking to support.

Check All Physical Connections

A loose cable can produce intermittent faults that appear much more complicated than they are.

Check:

• The router’s power cable
• The broadband cable
• Fibre connections
• Telephone-line cables
• Ethernet cables
• Wall sockets
• Filters
• Network switches
• Fibre termination equipment

Make sure each connector is fully inserted.

Do not force fibre connectors or bend fibre cables sharply. Fibre patch leads can be damaged more easily than ordinary Ethernet cables.

Check the Fibre Terminal or Modem

Full-fibre connections often use a separate optical network terminal, commonly called an ONT.

This device may have lights labelled:

• Power
• PON
• LOS
• LAN
• Alarm

A red LOS or loss-of-signal light may indicate that the optical connection has been interrupted.

Check that:

• The ONT has power.
• The Ethernet cable between the ONT and router is secure.
• The fibre cable has not been bent or pulled.
• No building work has disturbed the installation.

Do not open the ONT or disconnect the fibre unnecessarily.

Tell the ISP exactly which lights are illuminated or flashing.

Check Telephone Filters on Copper-Based Services

Broadband delivered through a telephone line may use filters or a filtered master socket.

Check that:

• Every required telephone device is correctly filtered.
• The router is connected to the broadband side of the filter.
• The filter is not damaged.
• Extension cables are not excessively long.
• The cable is not routed through an unsuitable telephone splitter.

Where possible, connect the router to the main test socket using a known-good filter.

A faulty filter or extension lead can cause:

• Slow speeds
• Dropouts
• Crackling calls
• Synchronisation problems

Listen for Noise on the Telephone Line

For broadband services using copper telephone lines, audible noise may indicate a line fault.

Using a corded phone where available, listen for:

• Crackling
• Buzzing
• Hissing
• Intermittent silence

A noisy voice line can affect broadband stability.

Avoid relying only on a cordless handset, because the handset itself may introduce noise.

Report an audible line fault to the provider. Do not describe it only as slow broadband.

Restart the Router Properly

A restart can clear temporary problems involving:

• Memory
• Wireless radios
• DHCP
• DNS forwarding
• Internet sessions
• Router software

To restart safely:

1. Switch the router off.
2. Wait around 30 seconds.
3. Turn it back on.
4. Allow several minutes for the connection to return.
5. Test again.

Do not repeatedly restart the router every few minutes.

On some line types, frequent disconnections may make the provider’s management system interpret the connection as unstable and temporarily reduce its profile.

Restart once, then observe the result.

Do Not Press the Reset Button

The reset button normally restores factory settings.

That can erase:

• Wi-Fi names
• Passwords
• Broadband login details
• Port-forwarding rules
• Guest-network settings
• Parental controls
• Business firewall configuration
• Phone settings

A factory reset is not the same as restarting.

Do not reset the router unless the provider or your IT support team specifically instructs you to do so and the necessary configuration has been recorded.

Check for a Local or National Outage

Before changing settings, check whether the provider has reported an outage.

Possible sources include:

• The provider’s service-status page
• Its mobile app
• Recorded support messages
• Official social-media support accounts
• Neighbours using the same service
• Business monitoring systems

An outage may affect:

• One exchange
• A postcode
• A region
• A specific broadband product
• Authentication services
• DNS
• Mobile backup services

If the provider has already acknowledged the fault, further local troubleshooting may not help.

Record the outage reference and expected restoration time.

Check Whether Your Account Is Active

A service can stop working because of an administrative issue rather than a technical fault.

Check for:

• Unpaid invoices
• Failed direct debits
• Contract changes
• A cancelled service
• A recently completed migration
• A new router awaiting activation
• Usage allowances
• A suspended mobile or satellite plan

Log in to the provider account using mobile data if necessary.

Be cautious with unexpected payment messages. Use the official app or website rather than following links from emails or texts.

Test More Than One Website

When one site is slow or unavailable, the broadband service may be fine.

Try:

• A search engine
• A news site
• A cloud service
• A video platform
• Another unrelated website

When only one destination fails, possible causes include:

• A website outage
• DNS problems
• Poor routing
• An expired certificate
• A browser problem
• Service-specific blocking
• The site rejecting your public IP address

Contacting the ISP may not resolve a fault controlled by the website operator.

Test More Than One Application

Compare:

• Web browsing
• Email
• Streaming
• Gaming
• Video calling
• Cloud storage
• Messaging

If browsing works but one app fails, investigate that app first.

Check:

• Service status
• Application updates
• Account login
• Subscription status
• Firewall settings
• VPN compatibility

A provider-wide problem normally affects more than one unrelated service.

Try Another Browser

A browser extension, corrupted cache or security setting can make the internet appear broken.

Try:

• A private browsing window
• Another browser
• Clearing the affected site’s cache
• Disabling extensions temporarily
• Restarting the browser

When the site works in another browser, the broadband connection is unlikely to be the cause.

Check Whether a VPN Is Active

A VPN changes the route your traffic takes.

A slow, distant or overloaded VPN server can cause:

• Slow downloads
• High latency
• Failed websites
• Streaming problems
• Video-call issues
• Authentication errors

Temporarily disconnect the VPN and test again, provided it is not required by your employer.

If the problem disappears:

• Select a nearer VPN server.
• Update the VPN software.
• Check split-tunnelling settings.
• Contact the VPN provider.
• Speak to business IT.

Do not disable an organisation’s mandatory security controls without approval.

Check Security and Filtering Software

Security applications can block traffic accidentally.

Possible causes include:

• Antivirus web filtering
• Third-party firewalls
• Parental controls
• DNS filtering
• Ad-blocking services
• Secure web gateways
• Endpoint protection
• Router content filters

Do not uninstall all security software.

Temporarily pause only the relevant feature where safe and authorised, then test.

When disabling a control fixes the problem, update or reconfigure it rather than leaving the device unprotected.

Check DNS

DNS converts names such as example.com into IP addresses.

A DNS problem can make websites appear slow or unavailable even when the internet connection itself works.

Signs include:

• Websites fail by name but work by IP address.
• Apps connect while browsers do not.
• Pages pause before loading.
• Some domains work while others fail.
• Restarting the router helps temporarily.

On Windows, you can test with:

nslookup example.com

On macOS or Linux:

dig example.com

or:

nslookup example.com

Do not change DNS settings randomly. Record the current configuration first.

A reputable alternative DNS provider may help with diagnosis, but it will not fix a damaged broadband line or weak Wi-Fi.

Check the Device’s IP Address

A device needs a valid local IP address, gateway and DNS configuration.

On Windows, run:

ipconfig

Look for an address resembling:

192.168.1.25

or another private network range.

An address beginning with:

169.254

usually means the device failed to receive an address from the router.

Possible causes include:

• DHCP failure
• A disconnected cable
• Wi-Fi authentication problems
• A faulty router
• A failed switch
• Incorrect static settings

Restart the device and reconnect to the network.

Ping the Router

Pinging the router helps determine whether the local network is stable.

The router address may be:

192.168.1.1

or:

192.168.0.1

On Windows:

ping 192.168.1.1

For a continuous test:

ping -t 192.168.1.1

On macOS or Linux:

ping 192.168.1.1

Look for:

• Low, consistent response times
• No packet loss
• No repeated timeouts

High or unstable first-hop latency points towards the local network rather than the ISP.

Test over Ethernet for the clearest result.

Ping an Internet Address

Next, test a reliable external IP address:

ping 1.1.1.1

or:

ping 8.8.8.8

Possible interpretations:

Router responds, external IP does not

The local network is working, but the internet connection may be down.

External IP responds, website names do not

DNS may be the problem.

Neither responds

The issue may be local, router-related or provider-related.

Some networks block ping, so use it as one piece of evidence rather than a final verdict.

Run a Traceroute

Traceroute shows the path from your device towards an internet destination.

On Windows:

tracert 1.1.1.1

On macOS or Linux:

traceroute 1.1.1.1

Look for:

• Whether the route leaves your router
• Where latency increases
• Where the trace stops
• Whether several destinations show the same pattern

Asterisks do not automatically indicate a fault. Some routers simply do not respond to traceroute probes.

Provide the full output to technical support rather than highlighting one slow-looking intermediate hop.

Run a Speed Test Over Ethernet

A meaningful broadband speed test should be performed:

• On a capable computer
• Over Ethernet
• With Wi-Fi disabled on that computer
• Without a VPN
• While other large transfers are paused
• Using more than one test service

Record:

• Download speed
• Upload speed
• Idle latency
• Loaded latency
• Jitter
• Packet loss
• Test server
• Date and time

One poor test is not enough. Repeat it several times.

Compare the Result With Your Contract

Check the provider’s documentation for:

• Expected download range
• Expected upload range
• Minimum guaranteed speed
• Peak-time estimate
• Any usage limits

Do not compare only with the largest headline number used in advertising.

Broadband overhead, local network limitations and service type can affect the usable rate, but persistent wired results below the promised range should be investigated.

Test at Different Times

A connection that works in the morning but slows every evening may be affected by:

• Provider congestion
• Neighbouring Wi-Fi
• Household demand
• Streaming-service demand
• Mobile-network load
• Business backup schedules

Run tests during:

• Early morning
• Working hours
• Peak evening time
• Late night

Keep the test method consistent.

A time-based pattern is valuable evidence.

Check What Other Devices Are Doing

A single device can consume most of the connection without being obvious.

Look for:

• Game downloads
• Operating-system updates
• Cloud backups
• Photo synchronisation
• CCTV uploads
• Streaming
• File-sharing
• Software deployment
• NAS replication

Check the router’s traffic monitor where available.

Pause large transfers and test again.

If the connection immediately improves, the ISP may not be the problem.

Check Upload Saturation

Consumer broadband often provides much less upload capacity than download capacity.

A large upload can make the entire connection feel slow.

Symptoms include:

• Delayed web browsing
• Poor video calls
• Gaming lag
• Robotic audio
• High latency
• Slow downloads despite unused downstream capacity

Pause:

• Cloud backups
• Security-camera uploads
• File synchronisation
• Large email attachments
• Livestreaming

If performance improves, consider:

• Scheduling uploads
• Limiting backup speeds
• Configuring queue management
• Upgrading to a service with more upstream capacity

Check Loaded Latency

Run a continuous ping while starting a large download or upload.

When latency rises from 15 milliseconds to several hundred milliseconds, the problem may be excessive queuing or bufferbloat.

This can happen even when the speed test reaches the advertised bandwidth.

A provider upgrade might help when the connection is genuinely saturated, but router traffic management may also be required.

Check Router Placement

When the problem affects Wi-Fi, inspect where the router is located.

Poor positions include:

• Inside a cupboard
• Behind a television
• On the floor
• Beside a microwave
• Next to a boiler
• Near large metal objects
• In a basement
• At one end of a large house

A better location is:

• Central
• Elevated
• Open
• Ventilated
• Away from interference

The ISP is not responsible for every weak Wi-Fi area inside the property, particularly when the incoming service performs correctly over Ethernet.

Check Mesh Nodes and Extenders

A mesh node can show a strong local signal while having a weak connection to the main router.

Check the mesh application for:

• Backhaul quality
• Offline nodes
• Incorrect placement
• Firmware updates
• Excessive wireless hops

Basic Wi-Fi extenders can reduce capacity and increase latency.

Test near the main router or over Ethernet before blaming the broadband line.

Check Ethernet Link Speed

A computer connected with Ethernet may negotiate at only 100 Mbps instead of 1 Gbps or faster.

Possible causes include:

• A damaged cable
• A poor connector
• An old network switch
• A 100 Mbps router port
• Incorrect adapter settings
• Missing cable pairs

If you have a 500 Mbps broadband package but the Ethernet link is 100 Mbps, the speed test cannot exceed the local link’s capacity.

Check the adapter status and switch or router port.

Try Another Ethernet Cable

A cable can partly fail without disconnecting completely.

Symptoms include:

• Reduced link speed
• Intermittent packet loss
• Disconnections
• Slow transfers
• Link lights repeatedly changing

Test with a known-good Cat 5e, Cat 6 or better cable.

Avoid damaged connectors and excessively tight bends.

Bypass Additional Network Equipment

Temporarily remove non-essential equipment from the path.

This may include:

• Network switches
• Powerline adapters
• Personal routers
• Mesh systems
• Hardware firewalls
• Ethernet-over-coax adapters
• USB network adapters

Connect a test computer as directly as safely possible to the provider router.

If the problem disappears, reconnect devices one at a time until the fault returns.

Check for Double NAT

Double NAT occurs when two devices are both acting as routers.

It commonly happens when:

• A personal router is connected behind the ISP router.
• A mesh system is left in router mode.
• A firewall is installed without bridging the provider equipment.

Double NAT does not normally reduce ordinary download speed dramatically, but it can affect:

• Gaming
• VPN servers
• Port forwarding
• Remote access
• Peer-to-peer applications
• Local discovery

Check the WAN address of your personal router. If it receives a private address such as 192.168.x.x, another router may be upstream.

Check for Overheating

Routers, modems and switches can become unstable when they overheat.

Ensure that equipment is:

• In the open
• Properly ventilated
• Not covered
• Not stacked tightly
• Away from radiators
• Away from direct sunlight
• Using the correct power adapter

Signs of overheating include:

• Random restarts
• Performance worsening over time
• Wi-Fi disappearing
• Hot casing
• Instability under heavy traffic

Allow the equipment to cool and test again.

Check Router Firmware

Outdated firmware can cause:

• Connection drops
• Wi-Fi faults
• Security problems
• Performance issues
• Compatibility problems

Provider-supplied routers often update automatically.

Third-party routers may require manual updates through their administration page or app.

Back up the configuration before performing a major firmware upgrade.

Do not install firmware intended for a similar but different model.

Check Whether the Router Is Still Supported

An old router may no longer receive security or reliability updates.

It may also be unable to handle:

• Modern broadband speeds
• Large numbers of devices
• Advanced encryption
• Current Wi-Fi standards
• VPN throughput
• Security filtering

Ask the provider whether the supplied router is still supported and whether a replacement is available.

A new router will not repair a faulty broadband line, but unsupported hardware should not be relied upon indefinitely.

Test Without Powerline Adapters

Powerline adapters use the electrical wiring to carry network traffic.

Their performance can change because of:

• Appliances
• Wiring quality
• Extension leads
• Circuit boundaries
• Surge protectors
• Electrical noise

Connect directly through Ethernet or Wi-Fi for comparison.

If the problem disappears, the powerline link—not the ISP—is the likely cause.

Check the Weather and External Cabling

External copper, coaxial or fibre cabling may be affected by:

• Water ingress
• Storm damage
• Tree branches
• Construction work
• Loose overhead cables
• Damaged street cabinets
• Accidental excavation

Do not climb poles or touch damaged external cables.

Report:

• Visible damage
• Hanging wires
• Open cabinets
• Water ingress
• A fault beginning after bad weather or nearby construction

Take photographs from a safe location.

Ask Neighbours

When nearby customers using the same provider experience the same problem, a local network or infrastructure fault becomes more likely.

Ask whether they have:

• No service
• Slow evening performance
• Frequent disconnections
• A red router light
• A known outage reference

Do not share account credentials or allow unknown people to access your router.

Keep a Fault Log

Intermittent faults are difficult to investigate without dates and times.

Record:

• When the problem starts
• How long it lasts
• Which devices are affected
• Whether Ethernet is affected
• Router light status
• Speed-test results
• Ping and packet loss
• Weather conditions
• Router restarts
• Error messages
• Any outage references

A short table is often enough:

This evidence gives the provider something measurable to investigate.

Prepare the Information the ISP Will Ask For

Before calling, have the following ready:

• Account holder’s name
• Service address
• Account or telephone number
• Router model
• Serial number where relevant
• Broadband type
• Router light status
• Time the fault began
• Devices affected
• Whether Ethernet was tested
• Speed-test results
• Error messages
• Troubleshooting already completed
• Outage reference
• Availability for an engineer visit

Do not post account numbers or serial numbers publicly.

Describe the Fault Precisely

Instead of saying:

“My internet is terrible.”

Say:

“All devices are affected. I tested a laptop by Ethernet directly to the provider router. The normal wired speed is around 450 Mbps, but between 7pm and 10pm it falls below 50 Mbps. The router remains connected and latency rises from 15 ms to over 100 ms.”

A precise description helps the support agent follow the correct process.

Ask the ISP to Check the Right Things

Depending on the connection type, ask the provider to check:

• Line status
• Synchronisation history
• Error counts
• Signal levels
• Optical levels
• Disconnection history
• Local congestion
• Account authentication
• Router health
• Network outages
• Minimum guaranteed speed
• Traffic-management policies

Do not demand an engineer visit before basic remote checks have been completed. Equally, do not accept repeated router restarts when the evidence shows a persistent external fault.

Ask for a Fault Reference

Always request:

• A ticket number
• A fault reference
• The expected next action
• A response timeframe
• Any test window
• Engineer details where booked

Keep notes of:

• Date and time
• Person or team spoken to
• Advice given
• Changes made
• Promised follow-up

This becomes important when the fault continues across several calls.

Do Not Cancel an Engineer Visit Too Quickly

An intermittent fault may disappear temporarily after:

• A router restart
• A line reset
• A weather change
• Reduced peak-time demand

If the problem has been recurring, confirm that it remains resolved over a reasonable period before cancelling an arranged investigation.

Keep the fault log until the service has remained stable.

Be Careful With Chargeable Visits

Providers may charge when an engineer finds that the fault is caused by:

• Customer-owned equipment
• Damaged internal wiring
• Incorrect installation
• An unsupported extension
• Accidental damage

Before agreeing to a visit, ask:

• Whether charges are possible
• Which conditions trigger them
• Whether internal wiring is included
• Whether the router is covered
• Who owns the affected equipment

Document the troubleshooting you performed.

When You Should Call the ISP Immediately

Contact the provider promptly when:

• The fibre terminal shows a loss-of-signal alarm.
• External cables are visibly damaged.
• Every device is offline.
• The router cannot establish broadband synchronisation.
• There is persistent wired packet loss.
• The service repeatedly disconnects.
• The line is noisy.
• Wired speeds remain below the guaranteed level.
• A provider outage is suspected but not listed.
• The connection failed after an engineer or service migration.
• Business-critical services are affected.

Do not spend hours changing Wi-Fi settings when the physical broadband connection is clearly down.

When the ISP Is Probably Not the Right First Call

Start elsewhere when:

• Only one website is affected.
• Only one application fails.
• Only one computer is affected.
• Ethernet works but one room has weak Wi-Fi.
• The issue appears only when a VPN is active.
• A local switch or powerline adapter is failing.
• The problem began after changing firewall settings.
• The service works on another browser.
• The streaming platform has an outage.
• A company-managed device fails while personal devices work.

In these cases, contact the application provider, device manufacturer or IT support team as appropriate.

A Practical Pre-Call Checklist

Before contacting the ISP, confirm that you have:

• Tested more than one device
• Compared Wi-Fi and Ethernet
• Checked router and modem lights
• Inspected physical cables
• Restarted the router once
• Checked for an outage
• Confirmed the account is active
• Tested more than one website
• Disconnected any optional VPN
• Paused large downloads and uploads
• Run a wired speed test
• Checked latency and packet loss
• Recorded dates and times
• Collected any error messages
• Prepared the account details

You do not need to complete every advanced step when the connection is completely offline. Use the checks that fit the symptom.

Give the ISP Evidence, Not Guesswork

The most effective support calls begin with a clear distinction between:

• A device problem
• A Wi-Fi problem
• A local-network problem
• A router problem
• A broadband-line problem
• A provider-network problem
• A service-specific problem

A few controlled tests can establish that distinction.

When the provider receives wired speed results, router-light information, packet-loss data and a reliable timeline, it is much easier to investigate the real fault.

Hamilton Group can diagnose broadband, Wi-Fi, routers, cabling, packet loss and business connectivity problems before or alongside an ISP investigation.

Call 0330 043 0069 or visit hgmssp.com to speak with one of our experts.