DNS resolution failed
Why FTP/SFTP DNS lookups fail and how to fix hostname resolution issues quickly.
Diagnose this automatically
Check whether the hostname resolves before debugging credentials or firewall rules.
Shareable output
Prefer the browser? Run the same check on the homepage.
If DNS resolution fails, the hostname can’t be converted into an IP address.
This is usually a typo, missing DNS record, or a DNS/VPN/network resolver issue.
Common causes
- Misspelled hostname
- DNS record does not exist (NXDOMAIN)
- Internal hostname used outside the VPN/network
- Local DNS resolver misconfiguration
- Intermittent DNS failures (timeouts / SERVFAIL)
Fix checklist
- Verify the hostname spelling (copy/paste; watch trailing spaces).
- Run `nslookup <host>` or `dig <host>` from your network.
- If the hostname is internal-only, connect via VPN or run checks from inside the network.
- Try an alternate resolver (1.1.1.1 / 8.8.8.8) if allowed.
Quick commands
nslookup <host>
dig +short <host>
ping <host> # only to test resolution; ICMP may be blockedFTPMonitor Help
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Related
- TCP connection timeout (firewall issue) — Why FTP/SFTP connections time out and how to diagnose firewall, routing, or allowlist blocking.
- TCP connection failed — General TCP failure causes when connecting to FTP, FTPS, or SFTP services.
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