> For the complete documentation index, see [llms.txt](https://developers.oxylabs.io/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://developers.oxylabs.io/products/proxies/dedicated-isp-proxies/self-service/response-codes.md).

# Response Codes

Learn about the common response codes and errors for Dedicated ISP Proxies and their meaning.

These are the most common response codes you can get while using Oxylabs Dedicated ISP Proxies.

<table><thead><tr><th width="166">Response code</th><th width="254.33333333333331">Error message</th><th>Description</th></tr></thead><tbody><tr><td><code>407</code></td><td><code>Proxy Authentication Required</code></td><td>User credentials are not provided / are incorrect / the user is connecting from an IP that is not whitelisted.</td></tr><tr><td><code>504</code></td><td><code>Gateway Timeout</code></td><td>A proxy server timed out, waiting for a response from the target server. It usually takes about 60s.</td></tr><tr><td><code>503</code></td><td><code>Service Unavailable</code></td><td>Failed to connect to the target server. DNS failure to resolve the target server address.</td></tr><tr><td><code>404</code></td><td><code>Not Found</code></td><td>The domain specified could not be found.</td></tr><tr><td><code>500</code></td><td><code>Internal Server Error</code></td><td>We had a problem with our server. Try again later.</td></tr><tr><td><code>429</code></td><td><code>Too Many Requests</code></td><td>User has reached the thread/concurrent session limit.</td></tr></tbody></table>


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