Command Prompt can fix Windows-side causes of slow or unreliable internet, such as stale DNS entries or damaged network configuration. It cannot increase the speed included in your ISP plan. Start by inspecting the connection and testing the problem; use resets only when the symptoms point to them.
What Command Prompt can—and cannot—fix
CMD commands can refresh Windows networking settings, clear the computer’s DNS cache, and help gather evidence about a connection problem. They do not change your ISP’s service tier or repair congestion, a weak Wi-Fi signal, or a fault outside your computer. If only one PC is affected, Windows troubleshooting may help; if multiple devices are slow on the same network, investigate the router or contact your network administrator or ISP.
Inspect the connection before changing settings
Open Command Prompt as an administrator for commands that change networking settings. Start with read-only checks:
-
Run
ipconfig /all. It displays TCP/IP configuration for all adapters, including IP address, gateway, and DNS information. Compare the active adapter’s details with the network you intend to use. [Microsoft: ipconfig]#1 Best Overall
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Run
nslookup example.comto test name resolution through a DNS server. If names fail to resolve or the returned result differs from what you expect, DNS may be involved; this test alone does not establish that DNS is the cause of slow downloads. [Microsoft: Troubleshoot DNS client resolution issues]
Choose a command that matches the symptom
| Command or action | Best fit | Privilege and restart | What it changes |
|---|---|---|---|
ipconfig /flushdns |
Suspected stale or negative DNS cache entries | Run in an elevated Command Prompt; no restart is normally required | Clears the local DNS resolver cache |
ipconfig /release, then ipconfig /renew |
A DHCP-assigned address or lease needs refreshing | Elevated Command Prompt; no Windows restart is normally required, but the interface can disconnect temporarily | Releases and requests a DHCP address |
netsh winsock reset |
Suspected Winsock catalog corruption or a network problem following software changes | Elevated Command Prompt; restart Windows if prompted | Resets the Winsock catalog and removes custom Layered Service Providers |
netsh int ip reset |
Damaged TCP/IP configuration when simpler targeted steps have not helped | Elevated Command Prompt; restart Windows after the reset | Resets TCP/IP settings, including TCP/IP and DHCP parameters |
netsh int tcp show global |
Checking the current TCP global settings before considering a throughput-related change | Command Prompt; no restart is needed to view settings | Displays settings without changing them |
netsh trace capture commands |
A reproducible network or DNS failure that needs diagnosis | Elevated Command Prompt; stop the trace when finished | Captures diagnostic network trace data |
Microsoft documents the commands and their effects in its ipconfig, DNS troubleshooting, Winsock, TCP/IP reset, and TCP performance tuning guidance.
Clear DNS cache for a DNS-resolution problem
Run:
ipconfig /flushdns
This flushes and resets the local DNS client resolver cache. It is useful when cached entries—including negative entries from earlier failed lookups—are suspected. It does not increase raw connection bandwidth or change your ISP’s DNS service. Retry the affected site or application after flushing.
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Refresh a DHCP address when the adapter uses automatic addressing
Run these commands in order:
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ipconfig /release -
ipconfig /renew
Use this only when the adapter obtains its address automatically from DHCP. Releasing the lease can temporarily disconnect that interface while Windows requests a new one. Avoid doing this remotely if you depend on that same connection to reach the computer.
Reset Winsock only when the catalog may be damaged
Run:
netsh winsock reset
Winsock is the Windows interface applications use to communicate with network services. Microsoft says this command resets the Winsock catalog and removes custom Layered Service Providers, which can cause network problems. Restart Windows if prompted; do not treat the command as a routine speed tweak. [Microsoft: netsh winsock]
Reset TCP/IP only for damaged configuration
A TCP/IP reset changes more than the DNS cache or Winsock catalog. If important interface settings are configured manually, record or back them up first. Then, in an elevated Command Prompt, run:
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netsh int ip reset
netsh winsock reset
Restart Windows after running the reset sequence. Microsoft says the TCP/IP reset overwrites TCP/IP and DHCP parameters and “has the same effect as removing and reinstalling TCP/IP,” so use it when configuration is damaged—not as the first response to any slow-speed complaint. [Microsoft: Reset TCP/IP] [Microsoft: troubleshooting sequence]
Check TCP autotuning before changing it
TCP receive-window autotuning can affect throughput in particular TCP conditions; it is not a universal internet-speed setting. First inspect the current global settings:
netsh int tcp show global
If the symptoms point to a TCP throughput issue, and you have recorded the existing setting, Microsoft documents setting autotuning to normal with:
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netsh int tcp set global autotuninglevel=normal
Do not change it solely because a speed test is disappointing. The effect depends on the connection and configuration, and the command is not a guaranteed speed increase. [Microsoft: Network performance tuning]
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.When the commands do not solve it, capture evidence
If a DNS or network problem can be reproduced, a trace can give an administrator or support team more useful information than repeated resets. In an elevated Command Prompt, run the start command, reproduce the failure, and then stop the trace:
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netsh trace start capture=yes tracefile=c:%computername%_nettrace.etlBest Value
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While the trace is running, reproduce the problem—for example, attempt the lookup or connection that fails.
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netsh trace stop
Provide the resulting trace file to your network administrator or support channel. A trace can contain network diagnostic data, so share it only with a trusted support contact. Microsoft documents this capture procedure for DNS troubleshooting. [Microsoft: DNS trace procedure]
How to tell whether a CMD fix helped
After a targeted change—and any required restart—repeat the same test that exposed the problem. For a DNS issue, retry the affected name lookup or application. For a throughput issue, test under comparable conditions and confirm whether other devices on the same network are also affected. If the problem persists, keep the command output and trace for support rather than layering more resets on top of one another.
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