Network Tools I Use: 12 Reliable Resources for DNS, Email, HTTP, and Troubleshooting
When you manage websites, email systems, APIs, or cloud infrastructure, “network issues” can mean almost anything: a DNS record hasn’t propagated, email is failing SPF alignment, a TLS certificate is misconfigured, a firewall is blocking traffic, or a CDN is caching something it shouldn’t. The fastest way to get from suspicion to certainty is to use a set of dependable diagnostic tools—especially ones that give you consistent results and help you confirm changes from multiple vantage points.
This article is a resource-style roundup of the network tools I use most often. They’re mostly web-based (so you can use them from anywhere), they cover common scenarios (DNS, email, routing, HTTP headers, TLS), and they’re well-known enough to be trusted when you’re communicating findings to teammates or clients. I’ll also include practical notes—what each tool is best for, when I reach for it, and what to watch out for so you don’t misinterpret results.
How I Think About “Network Tools”
Before the list, it helps to categorize the typical problems these tools solve:
DNS visibility and correctness: Are the right records published? Are they accessible globally? Are resolvers caching old values?
Email authentication and deliverability: Are SPF, DKIM, and DMARC configured correctly? Are mail servers reachable? Are you on a blacklist?
HTTP behavior and edge caching: What headers are being returned? Is the CDN injecting something? Are redirects correct?
TLS/SSL configuration: Is the certificate valid? Is the chain complete? Are protocols and ciphers aligned with modern requirements?
Connectivity, routing, and latency: Is the host reachable? Where does the route fail? Are packets being filtered?
No single tool covers everything. The real trick is to combine them: validate DNS from multiple resolvers, confirm service behavior over HTTP, and cross-check email posture with independent analyzers. This “triangulation” saves time and reduces false conclusions.
1) WhatsMyDNS — DNS Propagation and Multi-Resolver Checks
WhatsMyDNS is my go-to for quickly checking whether a DNS record change is visible across multiple locations and resolvers. When you update an A record, CNAME, MX, TXT, or AAAA record, propagation is often less about “the whole internet” and more about caching behavior across recursive resolvers.
What I use it for:
Confirming whether a new A/AAAA record is being returned globally
Verifying TXT records (SPF, DKIM, DMARC) after changes
Spot-checking whether a CNAME is resolving correctly from various regions
Practical tip: If you still see old values, compare the TTL you set with what you’re observing. A low TTL helps, but it doesn’t override caches that already stored an older answer until it expires. Use WhatsMyDNS as a “global snapshot,” then confirm locally with a targeted query tool (like Google’s Dig) for deeper detail.
2) MXToolbox — Email and DNS Diagnostics in One Place
MXToolbox is an all-purpose favorite when email or DNS configuration comes into question. It provides a collection of tests—MX lookups, SPF checks, blacklist monitoring, SMTP diagnostics, and more.
What I use it for:
Validating MX records and mail routing expectations
Checking SPF syntax and common mistakes
Reviewing DMARC and DKIM-related visibility in DNS
Running quick blacklist checks when deliverability dips
Practical tip: MXToolbox is great for “is this basically correct?” checks. For deep deliverability posture, pair it with a dedicated DMARC analyzer and a real inbox placement strategy—but for day-to-day troubleshooting, it often catches the obvious issues quickly.
3) DNSChecker — A Second Opinion on Global DNS Propagation
DNSChecker serves a similar purpose to WhatsMyDNS, and I often use it as a cross-check. Different tools may query different resolver pools, and having a second perspective is useful when you’re trying to determine whether an issue is widespread or isolated to certain networks.
What I use it for:
Confirming propagation across another set of resolvers
Comparing results when a client reports “it’s still broken for me”
Practical tip: If DNSChecker shows the new value but a user still sees the old one, that’s a strong hint the user’s ISP resolver (or local network resolver) is caching old data, or the application is using its own DNS caching layer.
4) Google Admin Toolbox Dig — Targeted DNS Queries with Detailed Output
Google Admin Toolbox Dig is one of the simplest ways to perform precise DNS queries without relying on local command-line tools. It gives you control over the query type and displays useful details.
What I use it for:
Querying specific record types (TXT, CNAME, MX, NS, SOA)
Verifying authoritative answers and catching misconfigurations
Getting quick output to share in tickets or emails
Practical tip: If you’re diagnosing propagation, pay attention to authoritative name servers and the SOA record. Sometimes the issue isn’t propagation—it’s that changes weren’t made in the correct DNS zone or aren’t being served by the expected authoritative servers.
5) IntoDNS — DNS Health Checks and Delegation Validation
IntoDNS is valuable when you suspect deeper DNS hygiene issues: misconfigured delegation, missing glue records, inconsistent NS sets, or other problems that don’t show up in simple A record queries.
What I use it for:
Checking NS consistency across authoritative servers
Identifying lame delegations and missing glue
Spotting TTL and SOA issues that can cause intermittent resolution
Practical tip: Treat IntoDNS as a “structural audit.” If it reports problems, fix those before chasing symptoms like intermittent downtime or region-specific resolution failures.
6) SecurityTrails — DNS and Domain Intelligence
SecurityTrails offers DNS intelligence and historical data. It’s helpful when you inherit a domain and need to understand prior configurations, or when you’re investigating unexpected changes.
What I use it for:
Viewing historical DNS records for troubleshooting regressions
Understanding subdomains and related DNS footprint
Validating ownership or tracking down “mystery” endpoints
Practical tip: Historical data is context, not proof. If you’re handling security-sensitive investigations, validate findings with authoritative DNS queries and internal change logs.
7) SSL Labs (Qualys) — Deep TLS/SSL Configuration Testing
SSL Labs Server Test is one of the most recognized tools for evaluating TLS configuration on public-facing endpoints. It provides a comprehensive breakdown: certificate chain, protocol support, cipher suites, vulnerabilities, and overall scoring.
What I use it for:
Verifying certificate chain completeness and trust
Checking for legacy protocol exposure (e.g., outdated TLS versions)
Evaluating configuration after migrating load balancers or CDNs
Practical tip: Use SSL Labs after major changes (new CDN, new reverse proxy, certificate renewal automation). It often catches issues that only appear from an external client’s point of view, such as missing intermediate certificates.
8) HSTS Preload — Confirming HSTS Eligibility and Preload Status
HSTS Preload is not a general network debugging tool, but it’s important enough in real-world operations to keep in your toolkit. If you plan to enforce HTTPS with strict transport security, this site helps you verify whether your domain meets the criteria for browser preload lists.
What I use it for:
Checking current preload status
Validating that HSTS headers meet preload requirements
Understanding the implications before submitting a domain
Practical tip: Preloading is effectively a long-term commitment. Confirm that all subdomains support HTTPS if you use includeSubDomains, and ensure certificates and redirects are correct before submitting.
9) WebPageTest — Performance, Waterfalls, and Network-Level Loading Behavior
WebPageTest is primarily a performance tool, but it’s extremely useful for network troubleshooting related to web delivery: redirects, caching, CDN behavior, and third-party request timing. It provides waterfalls and detailed request/response information.
What I use it for:
Spotting redirect chains and mixed content issues
Seeing header behavior (cache-control, CDN headers, compression)
Testing from different geographies and connection profiles
Practical tip: If users report slow loads “only in certain regions,” run tests from those regions and compare waterfalls. You can often pinpoint a single third-party domain or misrouted CDN POP.
10) HTTPStatus.io — Visualizing Redirect Chains
HTTPStatus.io is a clean way to inspect redirects without manually following them. It shows each hop, status code, and response headers, which is ideal for diagnosing unexpected 301/302 behavior or HTTP-to-HTTPS enforcement issues.
What I use it for:
Auditing redirect chains during site migrations
Ensuring canonical host enforcement (www vs non-www)
Confirming HTTPS redirects behave consistently
Practical tip: Pay special attention to redirect loops, mixed scheme hops (HTTP → HTTPS → HTTP), and chain length. Excessive redirect hops cost time and can break certain clients.
11) Ping.eu — Quick Connectivity Tests (Ping, Traceroute, DNS, and More)
Ping.eu is a lightweight collection of network tests you can run from a remote server: ping, traceroute, DNS lookup, port checks, and WHOIS. It’s convenient when you need a fast “is it reachable from outside my network?” check.
What I use it for:
Testing reachability when I suspect local ISP routing issues
Running a quick port check (e.g., 443, 25, 587) externally
Getting a basic traceroute for route visualization
Practical tip: Remember that ICMP ping being blocked doesn’t always mean the service is down. Many environments block ICMP while allowing TCP/HTTPS. Use port checks and HTTP tests to confirm service availability.
12) IPinfo.io — Fast IP Intelligence and ASN Context
IPinfo.io is one of the quickest ways to get context around an IP address: ASN, organization, approximate location, and related metadata. This is especially helpful when you’re looking at logs, firewall events, or unexpected traffic patterns.
What I use it for:
Identifying whether an IP belongs to a cloud provider, ISP, or enterprise ASN
Understanding traffic sources during incidents
Validating that “allowed IPs” belong to the expected organization
Practical tip: Geolocation is not perfectly accurate. Use it as a clue, not a definitive answer—especially for compliance or security decisions.
How I Use These Tools in Real Scenarios
Scenario A: “My DNS change isn’t working”
If a DNS change appears “stuck,” I typically do the following:
Check global visibility with WhatsMyDNS and DNSChecker (A/AAAA/CNAME/TXT as needed).
Run a more targeted query using Google Admin Toolbox Dig to confirm the answer path and authoritative servers.
If results are inconsistent, run IntoDNS to look for delegation or NS inconsistencies.
Common root causes: high TTL, changes applied to the wrong DNS provider, stale records at recursive resolvers, split-horizon DNS (internal vs external), or a misconfigured CNAME/ALIAS at the zone apex.
Scenario B: “Email deliverability suddenly dropped”
When emails start bouncing or landing in spam:
Use MXToolbox to check MX, SMTP reachability, SPF basics, and blacklists.
Confirm TXT records for SPF/DKIM/DMARC with WhatsMyDNS (to see global visibility) and Google Dig (to confirm exact record content).
If the domain recently changed DNS providers, use IntoDNS to make sure delegation is correct.
Common root causes: SPF exceeding DNS lookup limits, missing DKIM record publication, DMARC policy misalignment, or a mail provider change without updating MX/TXT records everywhere.
Scenario C: “The site redirects incorrectly”
For redirect and header problems:
Use HTTPStatus.io to map the redirect chain quickly.
Use WebPageTest to see how redirects and caching impact load performance and whether third-party calls are a factor.
Common root causes: conflicting rules between app, load balancer, and CDN; mixed canonicalization (www/non-www); accidental redirect loops introduced during HTTPS enforcement.
Scenario D: “TLS errors for some users”
If only some clients see TLS warnings:
Run SSL Labs to identify chain issues, weak ciphers, or protocol incompatibilities.
Confirm HSTS posture and eligibility with HSTS Preload if you’re enforcing strict policies.
Common root causes: missing intermediate certificates, outdated TLS settings on older load balancers, or an HSTS configuration that doesn’t match actual subdomain coverage.
Tips for Getting Accurate Results
Cross-check with at least two tools when the stakes are high. Different resolver pools, caches, and vantage points can produce different results.
Know what “propagation” really means: it’s often caching, not a magical global delay. TTL values matter, but so does resolver behavior.
Differentiate between authoritative and recursive answers. If authoritative servers have the right record but users don’t, you’re likely dealing with caching or resolver issues.
Document before/after output. For changes and incident reports, copy results from tools like Google Dig, SSL Labs summaries, and redirect chain outputs.
Be mindful of privacy and sensitive domains. Some tools query public endpoints and may log requests. For internal services, prefer internal tooling and controlled vantage points.
My “Minimum Kit” If You Only Bookmark a Few
If you want a short list that covers the most common needs:
WhatsMyDNS for fast DNS propagation checks
Google Admin Toolbox Dig for precise DNS queries
MXToolbox for email/DNS troubleshooting
SSL Labs for TLS configuration validation
HTTPStatus.io for redirect diagnostics
Closing Thoughts
A strong network toolkit doesn’t eliminate problems—but it shortens the path to clarity. The tools above are the ones I repeatedly come back to when diagnosing DNS changes, email delivery issues, TLS misconfigurations, and web routing behaviors. They’re especially effective when used together: confirm global DNS visibility, validate authoritative correctness, then test real service behavior over HTTP or SMTP.
As your environment grows—multiple CDNs, several mail streams, hybrid DNS, layered security controls—your troubleshooting process matters as much as the tools. Build a repeatable workflow, cross-check results, and keep notes. When the next “it’s down” message comes in, you’ll be ready to move from guesswork to evidence in minutes.