"The internet is down" is probably the most common phrase heard in any IT department — and in most homes, for that matter. After 20 years of responding to these calls, I can tell you that "the internet" is rarely actually down. Instead, there's usually a specific, identifiable problem at a specific layer of the network stack, and finding it requires systematic troubleshooting rather than random rebooting.
In this guide, I'll walk you through the systematic approach I use to diagnose network problems, from the physical layer all the way up to application-level issues. Along the way, I'll show you how to use common IP tools — many of which are available right here on IP Lobster — to pinpoint exactly where the problem lies.
The Bottom-Up Approach
Effective network troubleshooting follows the network stack from bottom to top. You start with the most basic physical layer and work your way up. There's no point investigating DNS issues if your Ethernet cable is unplugged, and there's no point calling your ISP if the problem is a misconfigured firewall on your own machine. Starting at the bottom and working up ensures you don't waste time on higher-level diagnostics when the problem is something fundamental.
Step 1: Check the Physical Layer
This sounds obvious, but you'd be amazed how often the solution to a network problem is a loose cable. Check that your Ethernet cable is firmly seated in both the device and the router or switch — you should hear and feel a click when it's properly connected. Look at the LED indicators on your network port and router. Most Ethernet ports have a green link light that indicates a physical connection and an amber activity light that flickers during data transfer. If there's no link light, the physical connection isn't established.
For Wi-Fi connections, verify that your wireless adapter is enabled. On laptops, check for a physical Wi-Fi toggle switch or function key combination. Verify you're connected to the correct network — it's surprisingly common for devices to silently connect to a neighbor's open network or a different SSID than intended. Check the Wi-Fi signal strength: if you're at the edge of your router's range, weak signal will cause intermittent connectivity and slow speeds.
Also check your router and modem. Are all the indicator lights showing normal status? Most ISP modems have a light for each layer of connectivity — power, downstream sync, upstream sync, and internet connection. If the internet light is off or flashing, the problem is between your modem and the ISP, not on your local network.
Step 2: Verify Your Local Network Configuration
Once you've confirmed the physical connection is solid, check your device's network configuration. On Windows, open a command prompt and run ipconfig. On Mac or Linux, use ifconfig or ip addr show. You're looking for several things.
Does your device have an IP address? If you see an address starting with 169.254.x.x, that's an APIPA (Automatic Private IP Addressing) address, which means your device couldn't reach the DHCP server (your router) and assigned itself a temporary address. This address won't work for internet access. The fix is usually to release and renew your DHCP lease: on Windows, run ipconfig /release followed by ipconfig /renew. On Linux, sudo dhclient -r followed by sudo dhclient.
Is the IP address in the expected range? If your router uses the 192.168.1.x subnet, your device should have an address in that range. An address in a different subnet means the device is misconfigured or connected to the wrong network.
Is the default gateway set correctly? The gateway should be your router's IP address. If it's blank or wrong, your device won't be able to route traffic beyond the local network.
Step 3: Test Local Network Connectivity
Ping your default gateway to verify you can communicate with your router: ping 192.168.1.1 (substituting your actual gateway address). If this fails, the problem is between your device and your router — a local network issue. If it succeeds, you know your local network is functioning correctly.
Common causes of local ping failures include: a misconfigured static IP or subnet mask, a wireless connection to the wrong network, MAC address filtering on the router blocking your device, or a faulty network adapter. Try connecting a different device to the same network to determine if the problem is specific to one device or affects the entire network.
Step 4: Test Internet Connectivity
If you can ping your gateway but can't browse the web, the next step is to test whether you can reach the internet at all. Ping a reliable external IP address: ping 8.8.8.8 (Google's public DNS) or ping 1.1.1.1 (Cloudflare's DNS). These addresses are highly available and rarely down.
If this ping succeeds, your internet connection is working — the problem is likely DNS-related (because you can reach the internet by IP but websites won't load by name). Skip ahead to the DNS troubleshooting section.
If the ping fails but your gateway ping succeeded, the problem is between your router and the internet. This could be an ISP outage, a problem with your modem, or a configuration issue on your router's WAN interface. Check your ISP's status page (from a different connection, like your phone's cellular data) to see if there's a known outage in your area. Try rebooting your modem — power it off for 30 seconds, then power it back on and wait 2–3 minutes for it to fully reconnect to your ISP.
You can also verify your public IP by visiting IP Lobster. If the page loads and shows your IP address, your internet connection is working. If it doesn't load, but you can ping 8.8.8.8, the issue might be HTTP-specific rather than a complete connectivity failure.
Step 5: Diagnose DNS Issues
DNS problems are one of the most common causes of "the internet is broken" symptoms. The telltale sign is that you can ping IP addresses directly (like 8.8.8.8) but can't load websites by name. This means your internet connection is fine, but domain name resolution is failing.
Test DNS resolution by using nslookup google.com on Windows or dig google.com on Mac/Linux. If the query times out or returns an error, your configured DNS server isn't responding. Try switching to a different DNS server temporarily: change your DNS to 1.1.1.1 (Cloudflare) or 8.8.8.8 (Google) and test again.
On Windows, flush your DNS cache with ipconfig /flushdns to clear any stale or corrupted cached entries. On Mac, use sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder.
Use IP Lobster's DNS Lookup tool to test resolution from an external perspective. If the DNS lookup works from IP Lobster but fails from your machine, the problem is with your local DNS configuration. If it fails from IP Lobster too, the domain itself may have DNS problems.
Step 6: Trace the Route
When connectivity is partially working — maybe slow, or some sites work and others don't — a traceroute can identify where in the network path the problem occurs. On Windows, use tracert google.com. On Mac/Linux, use traceroute google.com. This command shows every router (hop) your traffic passes through between your device and the destination, along with the round-trip time to each hop.
In a healthy traceroute, you'll see incrementally increasing latency as packets travel further. If you see a sudden spike in latency at a specific hop, that router or the link to it is congested. If the traceroute stops entirely at a certain hop (showing asterisks), there's a block or failure at that point in the path.
Interpreting traceroute results requires knowing that the first hop is your router, the next few hops are typically your ISP's infrastructure, and subsequent hops are transit providers and the destination's network. If the problem appears within the first 2-3 hops, it's likely an ISP issue you should report to them. If it's further along the path, the issue is likely in a transit network or at the destination end — less likely something you can directly fix.
Step 7: Check for Firewall and Software Issues
If basic connectivity tests pass but specific applications don't work, a firewall or security software might be blocking the traffic. Temporarily disable your software firewall (Windows Defender Firewall, for example) and test again. If the application works with the firewall off, you need to create a rule to allow the specific traffic rather than leaving the firewall disabled.
Browser-specific issues can masquerade as network problems. If websites don't load in one browser but work in another, try clearing the affected browser's cache and cookies, disabling extensions (ad blockers and security extensions can sometimes interfere with site loading), and checking proxy settings — some malware configures browsers to route through malicious proxy servers.
Antivirus software with "web shield" or "traffic inspection" features can also cause connectivity issues, especially with HTTPS sites. These features work by intercepting encrypted traffic, and sometimes they interfere with legitimate connections. Check your antivirus settings if you're experiencing problems specifically with HTTPS websites.
Step 8: Test Speed and Performance
If everything connects but feels slow, the problem might be performance rather than connectivity. Use a speed test to check your actual throughput against what your ISP plan promises. If speeds are significantly below what you're paying for, the issue could be ISP-side congestion, Wi-Fi interference, or a bottleneck in your local network.
For Wi-Fi performance issues, try connecting via Ethernet to determine if the slowness is wireless-specific. Wi-Fi performance is affected by distance from the router, physical obstacles (walls, floors, appliances), interference from other wireless devices, and channel congestion from neighboring networks. Moving your router to a more central location, switching to a less congested Wi-Fi channel, or upgrading to a mesh network system can dramatically improve performance.
Check your router's connected device list to ensure no unauthorized devices are using your bandwidth. Also check for devices performing large background downloads or uploads that might be consuming your available bandwidth.
The Troubleshooting Cheat Sheet
When you hit a network problem, work through these steps in order: First, check cables and Wi-Fi connections. Second, verify your IP configuration with ipconfig or ip addr. Third, ping your gateway to test local connectivity. Fourth, ping 8.8.8.8 to test internet connectivity. Fifth, test DNS resolution with nslookup or dig. Sixth, run a traceroute to identify where packets are failing. Seventh, check firewalls and security software. Eighth, test performance with a speed test.
This systematic approach will identify the root cause of the vast majority of network problems you'll encounter. The tools available at IP Lobster — including the Port Scanner, DNS Lookup, IP Geolocation, and WHOIS Lookup — complement these steps by providing external perspectives on your network's configuration and reachability.