Whitelist an IP in Windows Defender and third-party firewalls

Quick answer

Sometimes a firewall blocks an address you trust — a remote server, a home device, a colleague’s connection. Whitelisting (allowing) that specific IP fixes it. Here’s how, and the safety discipline that keeps an allow-rule from becoming a hole.

Confirm the IP first

Before you allow anything, be certain of the exact address. If it’s your own remote connection you want to permit, check it on our homepage; if it’s a server, confirm its IP and that it’s the right one with our Reverse DNS tool. Whitelisting the wrong address either fails to help or opens access you didn’t intend.

Windows Defender Firewall

In Windows, open Windows Defender Firewall with Advanced Security, create a new Inbound Rule (or Outbound, as needed), choose a Custom rule, and under the Scope step specify the remote IP address you want to allow. Set the action to Allow the connection, and scope it to the specific ports/programs involved rather than everything. Naming the rule clearly helps you find and remove it later.

Third-party firewalls

Most third-party firewalls and security suites follow the same logic: create an allow rule, scope it to the specific remote IP (and ideally specific ports), and apply it. The terminology varies — “trusted IPs,” “exceptions,” “allow rules” — but the principle is identical: permit this address, for this purpose, and nothing broader.

The safety discipline

An allow-rule is a deliberate hole in your firewall, so keep it tight: whitelist a single /32 address rather than a broad range unless you truly need the range (see CIDR ranges), limit it to the specific ports the trusted source needs, and document why it exists. Over-broad allow-rules — a whole subnet when you meant one host, “any port” when you meant one — are a classic source of unintended exposure.

Dynamic IPs complicate it

If the address you’re allowing is dynamic, it’ll change and your rule will silently stop matching (or worse, later allow a stranger who inherits it). For a remote person on a changing IP, a VPN or a DDNS-based approach is more robust than whitelisting a moving target. Review allow-rules periodically and remove ones you no longer need.