Network Troubleshooting

1

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 分钟阅读

2

DNS 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 分钟阅读

3

Slow 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 分钟阅读

4

SSH 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 分钟阅读

5

SSL 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 分钟阅读

6

High 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 分钟阅读

7

Packet 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 分钟阅读

8

Port 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 分钟阅读

9

BGP 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 分钟阅读

10

DDoS 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 分钟阅读

11

Email 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 分钟阅读

12

VPN Not Connecting: Troubleshooting All Protocols

Debug VPN connection failures across WireGuard, OpenVPN, and IPsec/IKEv2, including firewall issues, DNS leaks, and MTU problems.

10 分钟阅读

13

Website 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 分钟阅读

14

IP 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 分钟阅读

15

Firewall 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 分钟阅读

16

IPv6 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 分钟阅读

17

Wi-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 分钟阅读

18

How 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 分钟阅读

19

Setting 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 分钟阅读

20

Complete 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 分钟阅读