tracepath and Path MTU Discovery on Linux
Small things work and big things hang. One unprivileged command finds the narrow link, and one iptables rule shows what a black hole looks like.
Linux
The Linux side of a network engineer's job. Articles tagged Linux cover interfaces, routing tables, neighbor states, NIC drivers, name resolution and the CLI tools used for testing from a real host.
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mtr: Continuous Path Monitoring on Linux
Loss and latency per hop against a link with 12 percent loss injected on purpose, and the one rule that separates real loss from cosmetic loss.
traceroute: UDP, ICMP, and TCP Modes Explained
Three probe types down one four hop path, the packets on the wire for each, and the ICMP rate limit that makes a perfect path look broken.
nmcli and nmtui: Managing Connections from the CLI
Devices against connection profiles, the activation step everybody forgets, and how to make a configuration survive a reboot.
ethtool: Link Speed, Duplex, Offloads, NIC Stats
The driver layer below the kernel: link settings, offloads that make packet captures disagree with the wire, rings, and where host-side drops show up.
ifconfig, route, netstat: Legacy net-tools to iproute2
The full command map, and the same host through both toolsets so you can see exactly what the legacy tools hide from you.
ARP on Linux: ip neigh, arp, and Neighbor States
The six-state neighbor machine walked live on a real lab, the tunables behind it, and why arp -n cannot show you any of it.
ip route: Managing the Linux Routing Table
Every field in a route line, get against show, blackhole routes, the replace gotcha, and policy routing with multiple tables.
The Linux ip Command: The Complete Guide
The grammar, the four objects you use every day, the output modifiers that make it readable, and how to create interfaces out of nothing.
tcpdump for Network Engineers: A Practical Reference
Interface selection, BPF filters, reading the output line, writing and re-filtering pcap files, and safe long captures - all from a live run of tcpdump 4.99.5 against IOS-XE routers. Includes the privilege drop that kills rotating captures, and a telnet password readable on the wire.
Verify IP Parameters on Windows, macOS, and Linux
Half of network-down tickets end at the client. Verify IP address, mask, gateway, and DNS on Windows, macOS, and Linux with the exact commands for each, including live output from a real Debian host.
Linux Ping Options Every Network Engineer Should Know
The iputils ping flags engineers actually use: -c/-i/-q for jitter, -s/-M for MTU, -D for timestamps, and the -I flag that fixes confusing IPv6 failures.