MongoDB Connection Failures: SRV String, Allowlist, and DNS

Symptom

Cannot reach cluster: ECONNREFUSED, timeout, or auth failed.

Root cause

Wrong connection-string shape, IP not allowlisted, or DNS/resolver trouble.

Fix, in order

1. Use the SRV string for managed clustersmongodb+srv://user:pass@cluster.x.mongodb.net/db
2. Check the IP allowlist (most common miss)# Atlas: Network Access -> add your egress IP or 0.0.0.0/0 for testing
3. Verify DNS resolves the SRV hostdig _mongodb._tcp.cluster.x.mongodb.net SRV

Prevent it coming back

Static egress IP + allowlist; never leave 0.0.0.0/0 in production.

Run it on clean infra

Spinning up a fresh box to reproduce or escape this error?

Managed cloud hosting

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Last reviewed 2026-10-02 · NinjaOps SEO grid · DevOps blog