Parent Domains and Subdomains in .NET NO_PROXY
Include the parent domain deliberately when a .NET environment proxy policy also needs to bypass its subdomains.
In .NET's documented environment-proxy rules, .example.com matches subdomains. It does not match example.com itself. That little distinction can split one service across two routes.
| Entry | Intended .NET match |
|---|---|
example.com | The parent hostname |
.example.com | Hostnames below that domain |
example.com,.example.com | Both groups |
Suppose the landing page uses the parent name and its API uses api.example.com. A list containing only the dotted form can send the landing page through the proxy while the API goes direct. The reverse mistake is listing only the parent and expecting every child to match. Inspect HttpClient.DefaultProxy.IsBypassed for the parent and a child to check the configured decision.
This applies to the environment policy used by the participating .NET HTTP client. An explicitly assigned IWebProxy, another handler implementation, or another runtime generation needs its own rules checked. Do not assume a browser's bypass list has become this environment list.
Also resist translating the setting into *.example.com by habit. The documented .NET environment syntax does not treat the asterisk as a general wildcard.
When comparing a working curl command with the application, preserve the literal URL in the report. “Same server” hides whether you requested the parent, a subdomain, or an IP address. Domain matching happens against that request input, not against your informal name for the service.