add an example about accessing internal workloads

This is specifically for accessing containers on the same network
when running network isolation

Author: yrobla

docs/toolhive/guides-ui/network-isolation.mdx

@@ -79,6 +79,19 @@ The configuration pictured below allows the MCP server to access
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+### Accessing other workloads on the same network
+
+To allow an MCP server to access other workloads on the same network, you need
+to configure network isolation to include the appropriate hostnames and ports.
+This is commonly needed when your MCP server needs to communicate with
+databases, APIs, or other services that are not publicly accessible.
+
+For example, in Docker environments, you can add `host.docker.internal` to
+access services on the host:
+
+- **Allowed hosts**: `host.docker.internal`
+- **Allowed ports**: `3000`
+
 ## Related information
 
 - [Run MCP servers](./run-mcp-servers.md)