How To • Router • Troubleshooting

How to Fix DNS Issues After Firmware Updates

This guide will help you restore your internet connection by troubleshooting DNS problems that often appear after a router firmware update. You will learn to diagnose whether the issue is with your router, device, or settings, and apply safe fixes to get back online.

Note: Steps may vary by device and router model. This guide focuses on safe, general methods.

Quick Answer

If you can't browse the web after a router update but other apps might work, try these steps immediately:

Restart your router and modem (power cycle).
Restart the device having connection issues.
On your device, renew its IP address and flush the DNS cache.
Check your router's admin panel to ensure DNS settings weren't reset.
Manually set your DNS servers to a public option like Google (8.8.8.8) or Cloudflare (1.1.1.1).

If this doesn’t work: The problem might be more specific. Follow the diagnostic flow and step-by-step guide below.

What you need

Before you start

Access to your router’s admin interface (IP address, username, and password).
A device connected to your network (Wi-Fi or Ethernet).
Basic ability to open command prompt or terminal on your computer.
Your modem (if it's a separate device).
Knowledge of any custom DNS you were using before the update.

Good to know

Public DNS server addresses (e.g., 8.8.8.8, 1.1.1.1).
How to find your device's IP address and gateway.
That a firmware update can reset certain router settings to defaults.
The difference between a router reboot and a factory reset.
How to check for connectivity using the ping command.

Diagnose the issue in 2 minutes

Follow this flow to pinpoint where the problem is:

Is it only one device or all devices?
- One device: Problem is likely on that device (DNS cache, IP settings).
- All devices: Problem is likely with the router or ISP.
On the affected device, can you ping an IP address but not a website?
- Open command line and type ping 8.8.8.8.
  - Success: You have internet connectivity, but DNS is broken.
  - Failure: You may have a broader connection issue (DHCP, physical link).
Try Wi-Fi vs. Ethernet on the same device.
- If one works and the other doesn’t, the issue might be with a specific radio or driver, not DNS.
Is a VPN active?
- Disconnect the VPN. If browsing works, the VPN's DNS is conflicting with the new router settings.

Quick checks & expected outcomes:

1. ping 8.8.8.8 → Should get "reply" lines.

2. ping google.com → Should translate the name and get replies. If not, DNS is failing.

3. Check router's WAN/Internet status light → Should be solid or blinking, not off.

Step-by-step guide

Step 1 — Power cycle your modem and router

This clears temporary glitches and re-establishes a clean connection with your ISP.

Turn off and unplug your modem and router.
Wait 60 seconds.
Plug in and turn on the modem first. Wait for all its lights to stabilize.
Then plug in and turn on the router. Wait for it to fully boot.

What you should see: Devices reconnect and the router's internet/WAN light turns solid.

Step 2 — Restart the problematic device

A simple reboot clears the device's network stack and local DNS cache.

Completely restart your computer, phone, or tablet.
After restarting, reconnect to the Wi-Fi network.

Step 3 — Flush DNS and renew IP on your device

This removes old, possibly corrupted DNS entries and fetches fresh network settings from the router.

Windows: Open Command Prompt as Admin. Run: ipconfig /flushdns then ipconfig /release followed by ipconfig /renew.

macOS: Open Terminal. Run: sudo dscacheutil -flushcache; sudo killall -HUP mDNSResponder. To renew IP, go to System Settings > Network, toggle your connection off/on.

Linux: Open Terminal. The command varies by distro. For systemd-resolved: sudo systemd-resolve --flush-caches. Renew IP via sudo dhclient -r then sudo dhclient.

What you should see: The commands execute without major errors. Your device gets a new IP address.

Step 4 — Log into your router's admin panel

Check if the firmware update reset critical DNS configuration.

Open a browser and enter your router's IP (e.g., 192.168.1.1).
Log in with your admin credentials.
Navigate to the Internet/WAN or DNS settings section.

Step 5 — Verify or set DNS servers on the router

Ensure DNS is set to reliable servers, not an invalid or missing entry.

Look for "DNS Server" settings. If set to "Obtain automatically from ISP," try changing to "Use the following DNS addresses."
Enter reliable public DNS addresses:
- Primary: 8.8.8.8 (Google)
- Secondary: 8.8.4.4 or 1.1.1.1 (Cloudflare)
Save settings. The router will likely restart.

What you should see: After the router restarts, connected devices should be able to resolve website names.

Step 6 — Set DNS manually on a single device (for testing)

If changing the router's DNS doesn't help, manually override DNS on one device to confirm the fix works.

Windows: Go to Control Panel > Network and Sharing > Change adapter settings. Right-click your connection > Properties > IPv4 > Properties. Select "Use the following DNS server addresses."

macOS: System Settings > Network. Click your connection > Details > DNS. Click the "+" to add 8.8.8.8 and 1.1.1.1.

Linux: Use network manager GUI or edit /etc/resolv.conf (temporary) to add nameserver 8.8.8.8.

Step 7 — Check for DHCP server changes

A firmware update might have altered the DHCP range or disabled the server, preventing devices from getting an IP.

In your router admin, find the LAN or DHCP settings.
Ensure the DHCP server is enabled.
The IP address range (e.g., 192.168.1.100 to 192.168.1.200) should be appropriate for your network.

Step 8 — As a last resort, consider a router factory reset

If all else fails, the firmware update may have introduced a corrupted configuration. A reset wipes all settings back to factory defaults.

Warning: You will lose all custom settings (Wi-Fi name, password, port forwards).
Find the small reset button on your router, usually on the back.
Use a paperclip to hold it down for about 10 seconds until all lights flash.
Set up the router again from scratch, reconfiguring Wi-Fi and security.

Common fixes by symptom

Connected but no internet (browser says "DNS_PROBE_FINISHED_NO_INTERNET")

Likely causes: Router's DNS settings are blank/invalid; DHCP isn't handing out DNS; ISP DNS is down.

Safe fixes: Set manual DNS on router (Step 5). Flush DNS on device (Step 3). Power cycle everything (Step 1).

When to stop: If manually setting DNS on your device works, but the router setting doesn't stick—the router firmware may be buggy.

Some websites don't open, others load fine

Likely causes: DNS server is slow or failing to resolve specific domains; DNS filtering or parental controls were re-enabled.

Safe fixes: Switch to a different public DNS provider. Check router for any active "Access Controls" or "Website Blocking" features.

When to stop: If the issue is consistent for the same websites across all devices and DNS changes don't help.

Very slow browsing after update

Likely causes: DNS server is geographically far; new firmware has buggy DNS caching; QoS settings were reset and are throttling.

Safe fixes: Use a DNS benchmark tool or try different DNS servers (e.g., Cloudflare, OpenDNS). Disable QoS/Smart Queue features to test.

When to stop: If speed tests (to IP addresses) are normal, but browsing is slow—it's almost certainly a DNS performance issue.

Device gets an IP but "No Internet" or limited connectivity

Likely causes: Router's internet connection isn't fully up; the gateway IP is wrong; firmware bug in the WAN/DHCP client.

Safe fixes: Check router's WAN status page. Power cycle modem/router in correct order. Try cloning your device's MAC address on the router.

When to stop: If the router itself shows "Disconnected" or "Failed" for its internet connection—the problem is upstream (modem/ISP).

Wi-Fi connected, Ethernet not working (or vice versa)

Likely causes: Firmware update disabled a network interface; VLAN settings were changed; separate SSID for bands is misconfigured.

Safe fixes: Check router settings for Ethernet port status and Wi-Fi radio enable/disable toggles. Ensure both 2.4Ghz and 5Ghz bands are on.

When to stop: If only one physical port on the router fails, it could be a hardware issue triggered by the update.

VPN breaks local network access or internet

Likely causes: New router firewall rules block VPN protocols; DNS is being forced through the VPN tunnel which is down.

Safe fixes: Disconnect VPN to test basic internet. Check VPN app settings for "split tunneling." Temporarily disable router's SPI firewall or "VPN Passthrough" settings.

When to stop: If internet works perfectly without the VPN but never with it, contact your VPN provider about compatibility with new router firmware.

Quick reference

Table A: What the metric means

Metric	Meaning for Your Network	Good Baseline
Latency (Ping)	Delay for a data packet to travel. High latency causes lag.	< 50 ms to your router; < 100 ms to major sites.
Jitter	Variation in latency. Causes choppy voice/video calls.	< 30 ms is acceptable for most uses.
Packet Loss	Percentage of data packets that never arrive.	0% is ideal. > 1% may cause noticeable issues.
Throughput	Actual download/upload speed you experience.	Should be > 80% of your ISP's advertised plan speed.
Signal Strength	Power of the Wi-Fi signal your device receives.	-50 dBm (excellent) to -70 dBm (fair). Below -80 dBm is poor.

Table B: Safe baseline settings (post-update check)

Setting Category	Recommended Safe Configuration
Wi-Fi Security	WPA2/WPA3 Personal (AES). Avoid WEP or WPA (TKIP).
DNS	Use manual, reliable servers (e.g., 8.8.8.8, 1.1.1.1) or verify ISP auto-assignment works.
Router Admin	Change default login password. Disable remote admin access.
Guest Network	Enable if needed, with a separate password and device isolation.
Updates	Enable automatic firmware updates only if your router model is stable. Otherwise, manual is safer.

Mind map summary

Post-Firmware DNS Issues
├── Diagnosis
│   ├── One device vs. All devices?
│   ├── Can ping IP but not website? → DNS Problem
│   └── Check Wi-Fi vs. Ethernet
├── Immediate Actions
│   ├── Power Cycle (Modem → Router)
│   ├── Restart Problem Device
│   └── Flush DNS & Renew IP on Device
├── Router-Level Fixes
│   ├── Log into Admin Panel
│   ├── Check/Set DNS Servers (Use 8.8.8.8, 1.1.1.1)
│   ├── Verify DHCP Server is ON
│   └── Check for reset Firewall/Filtering rules
├── Device-Level Fallbacks
│   ├── Set DNS manually on the device
│   ├── Disable VPN to test
│   └── Forget and reconnect to Wi-Fi network
└── Last Resort
    └── Factory Reset Router (Reconfigure from scratch)

Troubleshooting checklist

Device

Restart the device
Flush DNS cache
Renew IP address (DHCP)
Forget Wi-Fi network & reconnect
Set manual DNS (temporary test)
Disable VPN/firewall software

Router

Power cycle (modem first, then router)
Log into admin panel
Check WAN/Internet connection status
Verify and set DNS servers
Ensure DHCP server is enabled
Check for firmware re-rollback option

ISP & External

Check for ISP outage reports
Test with a different public DNS
Try a different device (phone/tablet)
Bypass router: connect modem directly to a PC
Note error messages and timestamps

When to escalate

Contacting your ISP

Do this if: The router shows no internet connection on its status page even after proper power cycling, or if connecting a computer directly to the modem also fails. This indicates a line or account issue.

Replacing your router

Consider this if: The router repeatedly loses settings, fails to broadcast Wi-Fi after resets, or exhibits hardware issues (overheating, dead ports) that started after the update. Factory reset did not resolve basic functions.

Asking IT support or a professional

Do this if: You have a complex network (VLANs, static IP assignments, custom firewall rules) that was working before the update and you are uncomfortable restoring it. Or if you suspect a serious firmware bug.

What to collect before you call:

Results of a speed test (to an IP address and a domain).
Router model and firmware version number.
Exact error messages from browser or OS.
Timeline: When you updated, when problems started.
Whether the issue affects wired, wireless, or both.

FAQ

Why would a firmware update break DNS?

Firmware updates can reset router configurations to factory defaults, which often includes DNS settings. They might also introduce bugs in the DNS proxy or DHCP server, or change how the router handles network traffic, causing conflicts with previously stable setups.

Is it safe to use public DNS like Google or Cloudflare?

Yes, for most users. Public DNS services are generally reliable, fast, and secure. They can also provide benefits like phishing protection (if supported) and bypass ISP-level DNS outages. The main trade-off is that you are trusting a third party with your DNS queries, which reveals the websites you visit to them instead of your ISP.

How can I tell if my ISP's DNS is down?

If all devices on your network fail to resolve website names, but manually setting your computer's DNS to 8.8.8.8 fixes browsing immediately, it's a strong indicator your ISP's DNS servers are having problems. You can also try pinging your ISP's DNS server IP directly (if you know it) and see if it responds.

What's the difference between flushing DNS and renewing IP?

Flushing DNS clears your device's local cache of website-to-IP address mappings. Renewing your IP releases your current local network address (like 192.168.1.105) and requests a fresh one from the router's DHCP server. They solve different problems: flushing fixes bad domain records, renewing fixes network configuration conflicts.

Should I enable automatic firmware updates on my router?

It's a trade-off. Automatic updates keep your router secure with the latest patches, but they can also introduce unexpected bugs or changes that break your setup, as this article highlights. For a stable network, manual updates after reading release notes might be safer. For security, automatic is better if your router model has a good update history.

Can I roll back to the previous firmware version?

Some router manufacturers allow you to manually install an older firmware file through the admin interface. However, many do not support official rollbacks due to security and compatibility risks. Check your router's support documentation or admin panel for a "Firmware Upgrade" section to see if an older file can be uploaded.

Why does my phone work but my laptop doesn't after the update?

This usually points to a device-specific issue, not a router-wide DNS failure. Your laptop likely has a stale DNS cache, an incorrect static IP/DNS setting, or a different network adapter driver that's handling the new network configuration poorly. Follow the device-specific steps (flush DNS, renew IP, forget network) on the laptop.

Will a factory reset delete my ISP login information?

Yes. A factory reset erases all configuration, including your ISP username and password (PPPoE), Wi-Fi names/passwords, port forwards, and DHCP reservations. You will need to have this information on hand to set up your internet connection again from scratch. For many connections (DHCP or cable), this info is auto-detected, but it's best to be prepared.

Sources and references

Microsoft Windows Documentation: ipconfig, netsh, and network reset procedures.
Apple macOS Support: Flushing DNS cache and network configuration guides.
Linux Man Pages: systemd-resolve, dhclient, and NetworkManager documentation.
Router Vendor General Support Guides (TP-Link, Netgear, Asus, etc.) for firmware update and reset processes.
IEEE 802.11 Standards Overview for Wi-Fi functionality post-update.
Networking Diagnostics Basics: ICMP, ping, and traceroute concepts.
DNS Fundamentals RFCs (e.g., RFC 1034, RFC 1035) explaining name resolution.
Home Network Security Best Practices from CISA and other security organizations.
Public DNS Service Provider Documentation (Google Public DNS, Cloudflare 1.1.1.1).
General concepts of DHCP and IP address management in home networks.

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