Networking Tools

2020-05-07

🧠 Everyday Network Troubleshooting: Tools You Should Know (and Actually Use)

Networking Tools

Whether you're debugging why a pod can't reach an endpoint or trying to figure out why your app's requests are timing out, networking tools are your first line of defense.

Here’s a curated, opinionated, and battle-tested list of tools I use (almost) daily. Each one comes with practical examples.

🚀 Connectivity & Reachability

🔹 ping

Checks if a host is alive using ICMP echo requests.

ping google.com
ping -c 4 192.168.1.1 # -c 4 is to send 4 packets

🔧 Tip: If ping doesn't work, the host could be up but blocking ICMP. Check firewall rules.

🔹 traceroute

Visualise the path packets take to a remote host. Great for pinpointing bottlenecks.

traceroute google.com
traceroute -I 192.168.1.1 # -I is to use ICMP echo requests

🧠 Use case: “Why is latency high between service A and B?” → traceroute.

🔹 nslookup

Simple tool for querying DNS. Quick and dirty.

nslookup google.com
nslookup 8.8.8.8

🔹 dig

More verbose and powerful DNS query tool than nslookup.

dig google.com
dig google.com ANY # ANY is to get all records
dig google.com A +short # A is to get A records
dig google.com AAAA +short # AAAA is to get AAAA records

🧠 Bonus: Use +trace to debug DNS resolution path:

dig +trace google.com
dig +trace google.com +short # +short is to get the IP address

🌐 Port Scanning & TCP Checks

🔹 netcat (nc)

The Swiss Army Knife of TCP/UDP.

nc -zv google.com 80
nc -l 1234  # Listen on port 1234
nc -zv 192.168.1.1 1-65535 # -z is to scan all ports

📡 Tip: nc can be used to spin up fake HTTP servers or test port exposure in firewalled networks.

🔹 telnet

Old school, but works.

telnet google.com 80

🎯 Can be used to debug HTTP, SMTP, Redis manually.

🛠 Interface & Routing Info

🔹 ip (modern)

ip addr show
ip route show
ip link set eth0 up

🔹 ifconfig (legacy but familiar)

ifconfig
ifconfig eth0 up

🔹 route (macOS)

route -n
route add default gw 192.168.1.1

📊 Monitoring Traffic & Usage

🔹 netstat

netstat -an
netstat -r

🔹 ss (modern netstat replacement)

ss -tuln
ss -s

🔹 tcpdump Capture packets like a boss.

tcpdump -i eth0
tcpdump -i eth0 -w capture.pcap

🎯 Combine with wireshark to visualize packets.

🔹 tshark CLI version of Wireshark.

tshark -i eth0
tshark -r capture.pcap

🔹 vnstat

Track bandwidth usage.

vnstat -l
vnstat -d

🔹 nload / nethogs

Real-time network I/O monitor per interface or per process.

bash

nload
nethogs

📶 Wireless Tools

iw
iwlist
iwconfig

🧠 These are useful on laptops, Raspberry Pi setups, or Linux wireless APs.

🔐 Security, Scanning & Recon

🔹 nmap

Port scanner and network mapper.

nmap google.com
nmap -sP 192.168.1.0/24

🧠 Pro tip: Use with -A for OS detection, versioning, script scanning.

🔹 whois

Lookup domain ownership.

whois google.com

🔹 lsof

See what ports your system is listening on.

lsof -i :80
lsof -i tcp

🔹 arp / arping

arp -a
arp -d 192.168.1.1

arping 192.168.1.1

🧠 Use for static IP-to-MAC mapping debugging or LAN sniffing.

🧪 Bandwidth Testing

🔹 iperf

Client-server bandwidth tester.

iperf -s          # Start server
iperf -c <ip>     # Run client against server

📦 Works great for diagnosing slow internal links or tunnels.

🔹 mtr

Combines ping + traceroute with live stats.

mtr google.com
mtr google.com
mtr -r google.com

🧠 Instant visibility into jitter, loss, and latency by hop.

🧠 Bonus Mentions

conntrack – Show conntrack entries
ssdp – Debug multicast/UPnP
ncdu – Disk usage but worth knowing if you're debugging slow apps
hostname – Quick check or change the hostname

🎯 My Top 5 Daily Use Tools

✨ Final Thoughts

These tools are deceptively simple—but when chained together, they help you uncover:

Firewall misconfigurations
DNS issues
Interface problems
Packet loss/jitter
Port blocks or misroutes
Host reachability vs app-level downtime

🛠️ Bookmark this. Refer to it next time you're troubleshooting networking issues.