Network Troubleshooting
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Practical troubleshooting guides for common network problems. Step-by-step diagnostics for connectivity, DNS, latency, VPN, and security issues.
Can't Connect to the Internet: Complete Diagnostic Guide
A systematic, step-by-step diagnostic guide for when you have no internet access — covering physical checks, IP configuration, DNS, ISP issues, and packet capture.
10 мин. чтенияDNS Not Resolving: Step-by-Step Fix
Diagnose and fix DNS resolution failures with cache flushing, server changes, resolv.conf inspection, nslookup and dig diagnostics, and DNSSEC troubleshooting.
9 мин. чтенияSlow Internet Speed: How to Diagnose and Fix
Measure your true internet speed, isolate whether the bottleneck is Wi-Fi, your router, your ISP, or your hardware, and apply targeted fixes including QoS and MTU tuning.
10 мин. чтенияSSH Connection Refused: Troubleshooting Guide
Systematically diagnose and fix SSH connection refused errors — covering sshd service status, firewall rules, key authentication failures, SSH config issues, and verbose debugging.
9 мин. чтенияSSL Certificate Errors: Causes and Solutions
Understand and fix SSL certificate errors including expired certificates, chain validation failures, self-signed warnings, mixed content issues, and HSTS problems.
9 мин. чтенияHigh Latency and Ping Issues: Root Cause Analysis
Diagnose high latency by distinguishing it from bandwidth issues, using ping and mtr to locate the bottleneck hop, and identifying ISP routing problems, peering disputes, and CDN misconfiguration.
10 мин. чтенияPacket Loss: Detection, Diagnosis, and Resolution
Detect and diagnose packet loss at every network layer — from faulty cables and switch errors through routing problems, ISP congestion, buffer bloat, and QoS prioritization.
10 мин. чтенияPort Blocked by ISP: How to Detect and Work Around
Detect ISP port blocking on common ports like 25, 80, and 443, and work around restrictions using alternative ports, SSH tunneling, Cloudflare Tunnel, and VPNs.
9 мин. чтенияBGP Route Leak Detection and Response
Understand BGP route leaks, their impact on internet traffic, how to detect them using looking glass tools and RPKI validation, and how to respond to and prevent future incidents.
11 мин. чтенияDDoS Attack Mitigation: Practical Response Guide
Identify DDoS attack types, take immediate mitigation steps, implement rate limiting, use CDN protection, and apply BGP blackholing and scrubbing center techniques.
12 мин. чтенияEmail Not Being Delivered: Complete Debugging Guide
Step-by-step guide to diagnosing email delivery failures — from SPF and DKIM misconfiguration to IP reputation and reverse DNS issues.
10 мин. чтенияVPN Not Connecting: Troubleshooting All Protocols
Debug VPN connection failures across WireGuard, OpenVPN, and IPsec/IKEv2, including firewall issues, DNS leaks, and MTU problems.
10 мин. чтенияWebsite Not Loading: Server-Side Checklist
A systematic server-side checklist for diagnosing why a website is not loading, from DNS propagation to SSL errors and reverse proxy misconfigurations.
9 мин. чтенияIP Address Conflict: Detection and Resolution
Learn how to detect and resolve IP address conflicts on your network, from ARP table inspection to DHCP lease management and IPAM tools.
8 мин. чтенияFirewall Blocking Legitimate Traffic: Debug Guide
Debug firewall rules that block legitimate traffic using iptables logs, AWS Security Group audits, tcpdump captures, and testing tools like telnet and nc.
10 мин. чтенияIPv6 Connectivity Issues: Dual-Stack Debugging
Debug IPv6 connectivity in dual-stack environments, including Router Advertisement problems, DHCPv6 vs SLAAC, Happy Eyeballs, and tunnel broker setup.
9 мин. чтенияWi-Fi Keeps Disconnecting: Complete Fix Guide
Fix Wi-Fi disconnections with channel interference scans, router firmware updates, driver fixes, and mesh network troubleshooting on Windows, Mac, and Linux.
9 мин. чтенияHow to Read and Interpret Traceroute Results
Learn to interpret traceroute output including asterisks, timeouts, ICMP rate limiting, asymmetric routing, and using mtr for continuous path analysis.
9 мин. чтенияSetting Up Reverse DNS (PTR Records) Correctly
A complete guide to setting up PTR records for email deliverability, including cloud provider configuration for AWS, GCP, and Azure, and verifying FCrDNS.
8 мин. чтенияComplete Network Performance Audit Checklist
A systematic network performance audit covering baseline measurement, bandwidth testing, latency mapping, packet loss analysis, DNS, TLS, HTTP/2, and TCP tuning.
12 мин. чтения