MODERN LINUX NETWORK TROUBLESHOOTING

1. REHAN 27.01.2026 / 14:58
🐧 MODERN LINUX NETWORK TROUBLESHOOTING – MADE SIMPLE!

Whether you’re using Ubuntu, Debian, Fedora, Arch, or RHEL-based systems, this light-theme infographic walks you through modern Linux networking commands step by step — from checking IPs and routing to DNS, NetworkManager, and packet capture 🌐💻

🐧 Modern Linux Network Troubleshooting Guide
Works on Ubuntu 20.04+, Debian 11+, RHEL/CentOS Stream, Rocky, Fedora, Arch

1️⃣ CHECK NETWORK INTERFACES & IP ADDRESS
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ip addr show
Purpose:
Shows IP addresses (IPv4/IPv6)
Confirms interface is UP
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ip link show
Purpose:
Checks physical/logical interface state (UP/DOWN)

2️⃣ CHECK DEFAULT GATEWAY & ROUTING
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ip route show
Purpose:
Displays routing table
Confirms default gateway exists
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ip route get 8.8.8.8
Purpose:
Shows which interface & gateway traffic uses

3️⃣ TEST CONNECTIVITY
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ping -c 4 127.0.0.1
Purpose:
Tests local TCP/IP stack
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ping -c 4 <gateway- ip>
Purpose:
Confirms LAN/router connectivity
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ping -c 4 8.8.8.8
Purpose:
Tests internet access without DNS
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ping -c 4 google.com
Purpose:
Tests DNS + internet

4️⃣ DNS TROUBLESHOOTING (Modern systemd)
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resolvectl status
Purpose:
Shows active DNS servers per interface
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resolvectl query google.com
Purpose:
Tests DNS resolution directly
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resolvectl flush-caches
Purpose:
Clears DNS cache

5️⃣ NETWORK MANAGER (Modern Linux)
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nmcli device status
Purpose:
Shows device state (connected, disconnected)
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nmcli connection show
Purpose:
Lists network profiles
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nmcli device wifi list
Purpose:
Scans available Wi-Fi networks

6️⃣ CHECK LISTENING PORTS & CONNECTIONS
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ss -tuln
Purpose:
Shows listening TCP/UDP ports
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ss -antp
Purpose:
Shows active connections and processes

7️⃣ ARP / NEIGHBOR ISSUES (Modern Replacement)
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ip neigh show
Purpose:
Shows ARP / neighbor table
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ip neigh flush all
Purpose:
Clears stale ARP entries

8️⃣ TRACE NETWORK PATH & LATENCY
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traceroute google. com
Purpose:
Finds where packets stop
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mtr google. com
Purpose:
Continuous latency & packet-loss analysis

9️⃣ RESTART NETWORK SERVICES (Correct Way)
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sudo systemctl restart NetworkManager
Purpose:
Safely restarts networking
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sudo nmcli networking off && sudo nmcli networking on
Purpose:
Soft reset without reboot

🔟 PACKET CAPTURE (ADVANCED)
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sudo tcpdump -i eth0
Purpose:
Captures raw packets for deep debugging

❌ AVOID THESE (Deprecated)
Command
Status
ifconfig
Deprecated
netstat
Replaced by ss
arp
Replaced by ip neigh
iwconfig
Replaced by nmcli / iw
/etc/init.d/networking
Legacy

🧠 RECOMMENDED TROUBLESHOOTING Order
ip addr show
ip route show
ping gateway
ping 8.8.8.8
resolvectl query
ss -tuln
traceroute / mtr

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