MongoDB Atlas “IP Not Whitelisted” / Connection Timeout: The Exact Fix for Nepali Dynamic IPs

Most home broadband providers in Nepal (WorldLink, Vianet, Subisu, Nepal Telecom) use **Carrier-Grade NAT (CGNAT)** with dynamic public IP pooling. Every time your fiber router reboots or your ISP refreshes leases, your public IP changes. When you created your Atlas cluster and clicked *"Add Current IP Address"*, Atlas whitelisted your IP for that day only. The next morning, your router has a new IP, and your terminal outputs: ```bash MongoServerSelectionError: connection timed out at Topology.selectServer (/node_modules/mongodb/lib/sdam/topology.js:285:38) reason: TopologyDescription { type: 'ReplicaSetNoPrimary', servers: Map(3) { ... } } ```

### Fix 1: For Local Development & College Projects (0.0.0.0/0) In MongoDB Atlas: 1. Go to **Security > Network Access** in the left sidebar. 2. Click **Add IP Address**. 3. Click **Allow Access from Anywhere** (`0.0.0.0/0`). 4. Set a comment like *'Development - Dynamic Nepal IP'* and click **Confirm**. *Note: This allows connections from any IP, but your database is STILL protected by your database user username and strong password. Ensure your password is at least 20 random characters.* ### Fix 2: Resolving DNS/SRV Lookup Failures on Nepali Routers Some local router DNS servers fail to resolve MongoDB's `mongodb+srv://` URI format. If you still get timeout errors after whitelisting: 1. Change your laptop's DNS servers to **Cloudflare (1.1.1.1)** or **Google (8.8.8.8)**. 2. Alternatively, in your Atlas dashboard, click **Connect > Drivers**, uncheck *"Use the latest driver format"*, and select the standard non-SRV connection string.