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How Eagle DNS Protects Against DDoS and DNS Spoofing

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Troubleshooting Common Eagle DNS Configuration IssuesEagle DNS is designed to be fast, secure, and flexible — but like any DNS solution, misconfigurations and environmental factors can cause resolution failures, slow lookups, or unexpected behavior. This guide walks through the most common Eagle DNS configuration issues, how to diagnose them, and practical fixes you can apply to restore reliable DNS service.

1. DNS Resolution Fails Completely

Symptoms: Clients cannot resolve any domain through Eagle DNS; lookups time out or return SERVFAIL/NXDOMAIN.

Possible causes and fixes:

  • Eagle DNS service not running — Check the Eagle DNS daemon/process on your server. Restart it and inspect logs.
    • Command examples (Linux): 
      
sudo systemctl status eagledns sudo journalctl -u eagledns -f sudo systemctl restart eagledns
  • Firewall blocking DNS (port 53 UDP/TCP) — Ensure your firewall allows inbound UDP and TCP on port 53 for the DNS server IP.
  • Network routing issues — Verify the DNS server has correct network connectivity and default gateway; test with ping/traceroute to known IPs.
  • Upstream resolver problems — If Eagle DNS forwards queries, confirm upstream resolvers are reachable and healthy.
  • Configuration syntax errors — A malformed configuration file can prevent startup. Validate config using any built-in syntax-check tool or by reviewing logs for parse errors.

2. Intermittent or Slow DNS Responses

Symptoms: Some queries take long to answer; clients occasionally experience timeouts.

Possible causes and fixes:

  • High server load or resource exhaustion — Check CPU, memory, and file descriptor usage. Increase resources or tune limits if necessary.
    • Commands: 
      
top free -m ss -s ulimit -n
  • Large number of concurrent queries / DDoS — Implement rate-limiting, response rate limiting (RRL), or upstream filtering. Consider using any built-in DDoS protection features and enable query logging for suspicious patterns.
  • Recursive lookup loops or long TTL caching — Ensure recursion settings and cache behavior are correct. Clear cache if necessary to remove stale records.
  • Slow upstream resolvers — Test upstream latency with dig +trace or direct queries to the configured upstream IPs. Replace or add faster resolvers if they’re slow.

3. Incorrect Records Returned (Stale or Wrong Data)

Symptoms: DNS responses contain outdated IPs or incorrect records.

Possible causes and fixes:

  • Stale cache entries — Clear or flush Eagle DNS’s cache after changing authoritative records.
  • TTL misconfiguration — Verify TTL values in zone files. Lower TTLs during frequent change windows.
  • Multiple authoritative sources out of sync — If you run multiple authoritative servers or use DNS replication, ensure zone transfers (AXFR/IXFR) are succeeding and serial numbers are incremented properly.
  • Zone file format errors — Use zone validation tools to detect mis-ordered fields, missing semicolons, or malformed records.

4. Zone Transfer (AXFR/IXFR) Failures

Symptoms: Secondary servers fail to receive updated zones; transfers time out or are refused.

Possible causes and fixes:

  • Access control restrictions — Confirm allow-transfer or ACL settings on the primary server include the secondary’s IPs.
  • TSIG key mismatch — If you use TSIG for authentication, make sure keys and algorithms match exactly on both ends.
  • Firewall blocking TCP 53 — AXFR commonly uses TCP; verify TCP port 53 is open between primary and secondaries.
  • Serial number not incremented — Ensure the SOA serial is increased when zone changes are made; secondaries won’t pull new data otherwise.

5. Recursive Resolution Not Working as Expected

Symptoms: Eagle DNS configured for recursion either fails to answer recursive queries or disallows them for clients.

Possible causes and fixes:

  • Recursion disabled or restricted — Check recursion settings; enable for trusted networks and disable for open resolver exposure.
  • Access control lists (ACLs) — Confirm client IPs are permitted to use recursion.
  • DNSSEC validation issues — If DNSSEC validation is enabled, broken signatures or missing trust anchors can cause failures. Update trust anchors (e.g., root key) and verify zone signatures.
  • Forwarding misconfiguration — If forwarding is used, ensure forwarder IPs are reachable and configured to accept queries from your server.

6. DNSSEC and Signature Problems

Symptoms: Validation failures, SERVFAIL responses for signed zones, or clients rejecting records.

Possible causes and fixes:

  • Incorrect keys or expired signatures — Check that zone signing keys (ZSK/KSK) are valid and signatures haven’t expired. Re-sign zones if needed.
  • Missing or incorrect DS records in parent zone — Ensure DS records at the registrar/parent match the child zone’s KSK.
  • Outdated trust anchor — Update the root trust anchor if your resolver relies on a local copy.
  • Time skew — Ensure server time is correct (use NTP/chrony); DNSSEC is time-sensitive.

7. Split-Horizon / Split-View Zone Issues

Symptoms: Internal clients receive different records than external clients unexpectedly or not at all.

Possible causes and fixes:

  • View configuration errors — Verify view definitions and match-clients statements. Make sure ACLs for views are precise and non-overlapping.
  • Hostname/name overlaps — Ensure internal and external zones are distinct or correctly shadowed in views.
  • Zone loading order — Some servers load views/zones in a sequence; confirm both views load successfully and contain intended records.

8. Logging and Monitoring Gaps

Symptoms: You can’t find why problems occur because logs are sparse or missing.

Recommendations:

  • Enable query and error logging — Use selective logging to capture problematic clients or types without overwhelming storage.
  • Set log rotation and retention — Avoid filling disk space; route logs to a centralized system (syslog, ELK, Prometheus) for analysis.
  • Monitor key metrics — Query rate, cache hit ratio, error rates, latencies, and upstream availability. Set alerts for abnormal values.

9. Client-Side Misconfiguration

Symptoms: Server looks healthy but specific clients (or browsers) still can’t resolve.

Checklist:

  • Local DNS settings — Verify client DNS is set to the Eagle DNS server IP and no local overrides exist (e.g., /etc/hosts entries).
  • DNS caching on clients — Flush client DNS cache (Windows: ipconfig /flushdns; macOS: sudo dscacheutil -flushcache; browsers may have internal caches).
  • IPv4 vs IPv6 issues — Ensure server listens on the protocol family the client uses; test both A and AAAA queries.
  • Split DNS and VPN interactions — VPNs can override DNS; check VPN DNS settings and split-tunnel configuration.

10. Miscellaneous: Certificates, Management UI, and APIs

Symptoms: Web UI/API for Eagle DNS management fails or shows errors when applying changes.

Possible causes and fixes:

  • API authentication/permissions — Confirm API keys, tokens, and roles are correct and not expired.
  • Certificate problems in HTTPS UI — Replace expired TLS certs; ensure the certificate chain is complete and matches hostnames used.
  • Backend service dependencies — Check database connectivity, message queues, or other services the management UI depends on.
  • Race conditions on apply — Some systems require a reload/restart sequence for changes to take full effect; consult logs after applying changes.

Diagnostic Tools & Commands (Examples)

  • Basic DNS query: 
    
dig @your-eagle-dns-server example.com A +noall +answer
  • Trace path for DNS delegation: 
    
dig +trace example.com
  • Test specific record type: 
    
dig @your-eagle-dns-server example.com SOA
  • Check TCP vs UDP behavior: 
    
dig @your-eagle-dns-server example.com +tcp
  • Check zone transfer from primary: 
    
dig @primary-server example.com AXFR

Quick Checklist for Rapid Triage

  1. Is the Eagle DNS service running? Restart if necessary.
  2. Are ports 53 UDP/TCP open on server and firewalls?
  3. Can the server reach upstream resolvers and the internet?
  4. Are zone serials and signatures current?
  5. Are ACLs and recursion settings allowing intended clients?
  6. Is DNSSEC configured correctly and is server time accurate?
  7. Do client machines have correct DNS settings and cleared caches?
  8. Are logs enabled and monitored for anomalies?

If you’d like, provide your Eagle DNS config (redact private keys/IPs) and specific dig command outputs you’re seeing; I can point out likely misconfigurations and exact lines to change.

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