MongoDB Atlas AWS VPC Peering Not Connecting

How to fix it

Try these in order — the most common fix is first.

1. 1. Check the tier

   1. Network peering and private endpoints are not supported on Free (M0) clusters; use a Dedicated tier
   Did this fix it? Yes No

2. 2. Complete the peering

   Copy steps
   1. Accept the peering request in AWS
   2. Add a route for the Atlas CIDR to your route tables
   3. Add your VPC CIDR to Security > Network Access
   Did this fix it? Yes No

3. 3. Allow the port

   Copy steps
   1. Allow outbound TCP 27017 in the security group
   2. Test with nc -zv <node-host> 27017 from the instance
   Did this fix it? Yes No

4. 4. Check private endpoint DNS

   1. Verify DNS resolves the private endpoint hostname
   Did this fix it? Yes No

Symptoms

App in your VPC times out against Atlas while the public connection works.

Why it happens

• Peering unsupported on M0
• Route table lacks the Atlas CIDR
• Security group blocks 27017
• Peering not accepted or access list missing the VPC CIDR
• Private endpoint DNS misconfigured

This guide also covers

• mongodb atlas vpc peering not working
• mongodb atlas aws lambda connection
• atlas private endpoint timeout

The same problem in other apps

All not loading, error messages & connection guides →

• Supabase Max Client Connections Reached (Supabase)
• Firebase auth/invalid-api-key Error (Firebase)

Other MongoDB Atlas errors

• MongoDB Atlas Connection Timed Out (IP Not Whitelisted)
• MongoServerSelectionError: Fix for MongoDB Atlas
• MongoDB Atlas Authentication Failed (bad auth)
• MongoDB querySrv ENOTFOUND / ECONNREFUSED Error
• MongoDB Atlas Free Tier (M0) Limits and Throttling
• MongoDB Atlas Cluster Paused (Resume or Auto-Pause)
• MongoDB Atlas Unexpected Bill: Why It's So High
• MongoDB Atlas Too Many Connections Error