Network Troubleshooting Guide: Step-by-Step Solutions for IT

August 21, 2025

Network Troubleshooting: A Step-by-Step Guide for IT Professionals

Introduction

Even the most advanced networks break. When they do, you need more than intuition—you need a structured troubleshooting process. Whether you’re diagnosing a sluggish SaaS app, a failed connection between cloud services, or an unreachable internal server, network troubleshooting is a core skill every IT and DevOps professional must master.

This guide covers the tools, methods, and real-world workflows for diagnosing and fixing network issues—from physical cabling to DNS misconfigurations and routing errors. In the final section, we’ll show how noBGP eliminates entire classes of problems by changing the way networks are built and connected.

The Network Troubleshooting Process

Effective troubleshooting follows a structured approach. The most common model is OSI layer-based, progressing from physical connections to application-level issues.

OSI Model for Troubleshooting

Layer	Function	Examples of Issues
1	Physical	Cable unplugged, bad port
2	Data Link	MAC filtering, VLAN misconfig
3	Network	IP misconfig, routing failures
4	Transport	TCP/UDP port issues, firewall blocks
5–7	Session–Application	DNS errors, authentication failures

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Step-by-Step Troubleshooting Workflow

1. Define the Problem Clearly

What is broken?
Who is affected?
When did it start?

Good question: “Can host A ping host B?”

Bad question: “The network is down.”

2. Check Physical Layer (Layer 1)

Are cables connected?
Is the network interface up?
Try: ip link, ifconfig, link lights

3. Verify IP Configuration (Layer 3)

Is the IP address correct?
Does the subnet match?
Try: ip addr, ping, traceroute

4. Check Network Connectivity

Can you ping your gateway?
Can you reach the internet?
Try:

ping 8.8.8.8 traceroute google.com

5. Inspect DNS Resolution (Layer 7)

Is DNS working? Try:

nslookup example.com dig example.com

6. Test Port Availability (Layer 4)

Is the right port open?
Try:

nc -zv server.example.com 443 telnet server.example.com 22

7. Check Firewall Rules

Is the traffic being blocked?
Check:
- iptables (Linux)
- ufw, firewalld
- Security group policies (AWS/GCP)

8. Look for Routing Problems

Run:

ip route show traceroute

9. Capture Traffic (Advanced)

Use tcpdump or Wireshark to view live traffic
Filter for failed handshakes or dropped packets

Diagram: Troubleshooting Flow

networking troubleshooting workflow steps

Real-World Tools for Troubleshooting

Tool	Purpose
ping	Test connectivity
traceroute	Show path packets take
tcpdump	Packet capture and inspection
nslookup	DNS resolution
ip/ifconfig	Show network interfaces
nc / telnet	Test port-level connectivity
Wireshark	Deep packet analysis (GUI)
Cloud vendor logs	Audit traffic (AWS VPC Flow Logs)

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Common Network Problems and Fixes

Problem	Likely Cause	Fix
Cannot ping gateway	Cable unplugged or wrong IP	Check physical and Layer 3 config
Slow internet access	DNS lag, packet loss	Try alternate DNS, test latency
Remote service unreachable	Firewall rules or port block	Open port, allow IP
VPC to VPC traffic fails	Overlapping CIDRs, bad route tables	Use NAT, VPN, or redesign routes
Internal app not resolving	DNS record missing or stale	Flush DNS, fix record

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Troubleshooting in Modern Networks

In today’s infrastructure, networks are more complex:

Cloud-native apps: Move across nodes frequently
Multi-cloud: Require VPNs or peering to connect
Overlapping subnets: Cause routing failures
Ephemeral services: Spin up/down rapidly, breaking static rules

Traditional network troubleshooting assumes:

Static IPs
Predictable paths
Manual configuration

But that’s no longer the world we live in.

How noBGP Changes Network Troubleshooting

Troubleshooting modern networks often involves guessing where the problem lies across:

IPsec tunnels
NAT translations
DNS resolution delays
Cloud security policies
Complex BGP routes

noBGP eliminates most of these problems by providing:

Deterministic, Private Routing

You know exactly which path traffic takes—no more BGP guesswork.

Identity-Based Connections

Workloads talk to each other using identity, not IP. No subnet planning needed.

No NAT, No Overlapping IPs

noBGP allows overlapping CIDRs across VPCs—no collisions, no broken paths.

End-to-End Encryption by Default

No need to troubleshoot IPsec or TLS termination on routers.

Instant Logging and Policy Visibility

You can see what’s allowed, what was denied, and why—no hunting through AWS logs.

Summary: Troubleshooting with and without noBGP

Feature	Traditional Network	With noBGP
Troubleshooting path	Multi-layered guess	Deterministic, direct visibility
Subnet overlap issues	Frequent	Eliminated
DNS/NAT dependencies	Always involved	Not needed
Toolchain needed	Many	Minimal (built-in policies)
Configuration complexity	High	Low

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Final Thoughts

Network troubleshooting is a critical skill, but traditional methods are becoming more painful as infrastructure complexity grows. Static IPs, manual firewall rules, and BGP-based routing create brittle systems with long mean-time-to-resolution (MTTR).

With noBGP, you take back control. Traffic flows based on identity and policy—not on unpredictable public infrastructure. Troubleshooting is simpler, faster, and more transparent.

Why debug a pile of route tables when you could just know it works?

Choose your path with noBG

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