Essential Network Troubleshooting Commands: Ping, Traceroute, tcpdump, nmap and More

Testing network connectivity and diagnostics on Linux using common command‑line tools.

Basic commands:

ping
ip route
route
traceroute
tracepath
mtr
nslookup
host
dig
tcpdump
wireshark
nmap
netcat (nc)
tc

Example of traffic control with tc:

tc qdisc add dev eth0 root netem loss 50%
tc qdisc add dev eth0 root netem delay 1000ms
tc qdisc show dev eth0
tc qdisc del

fping

fping sends ICMP probes to multiple hosts efficiently. It supports specifying a list of hosts or a file and is faster than ping for many targets. Install via EPEL on CentOS.

# yum -y install fping
# fping 10.0.0.7
# fping -g 10.0.0.0/24

tcpdump

tcpdump captures network packets with powerful filtering options. Common syntax and parameters are listed, e.g., -i eth0, -nn, -c 100, and saving to a file.

tcpdump -i eth0 -nn icmp and src host 10.0.0.6 and dst host 10.0.0.7
tcpdump -c 100 -w ./target.cap

nmap

nmap scans remote hosts and ports, offering many scan types such as SYN (-sS), TCP connect (-sT), UDP (-sU), OS detection (-O), and version detection (-sV). Example commands illustrate host discovery, port scanning, and aggressive scanning.

# nmap -sS 10.0.0.1
# nmap -sU 10.0.0.1
# nmap -O 10.0.0.1
# nmap -A 10.0.0.1