Local interface, address, route, and neighbor state with iproute2. Use when viewing or configuring a host's own IPs, links, routes, or ARP/NDP cache — the ifconfig/route/arp replacement.
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Local interface, address, route, and neighbor state with iproute2. Use when viewing or configuring a host's own IPs, links, routes, or ARP/NDP cache — the ifconfig/route/arp replacement.
Trace the route or diagnose latency to a remote host
network-diagnostics (trippy, gping)
Find what process is listening on a port
network-diagnostics (ss)
Enumerate hosts on the local L2 segment
layer2-discovery (arp-scan, LLDP)
Discover which switch port a host is on
layer2-discovery (lldpcli)
Scan open ports on a remote host
network-discovery (RustScan, nmap)
Resolve DNS records for a domain
dns-tools (dog, dig)
Monitor per-process bandwidth
network-monitoring (bandwhich)
Load test an HTTP endpoint
http-load-testing (oha)
Expert knowledge for inspecting and configuring a Linux host's own Layer 2/3
state — addresses, links, routes, and the neighbor cache — with the iproute2
ip command. This is the modern replacement for the entire net-tools suite:
ifconfig, route, arp, and netstat -i/-r.
Platform note:ip (iproute2) is Linux-only. On macOS the equivalents
are ifconfig, netstat -rn, route -n get, and arp -a; this skill targets
Linux hosts and the many containers/VMs/servers you shell into.
iproute2 as the net-tools Replacement
Legacy (net-tools)
Modern (iproute2)
Shows
ifconfig
ip addr / ip a
Addresses per interface
ifconfig -a
ip link / ip l
Link state, MAC, MTU
route -n
ip route / ip r
Routing table
arp -a
ip neigh / ip n
ARP/NDP neighbor cache
netstat -i
ip -s link
Per-interface counters
netstat -g
ip maddr
Multicast group membership
ifconfig eth0 up
ip link set eth0 up
Bring interface up
ifconfig eth0 1.2.3.4/24
ip addr add 1.2.3.4/24 dev eth0
Assign address
route add …
ip route add …
Add a route
net-tools is unmaintained and blind to modern kernel features (multiple
routing tables, policy rules, VRFs, network namespaces, IPv6 details). Prefer
ip on any Linux host.
Global Flags — the Throughline
These modify anyip object and compose freely. The first three are the
core habit:
Flag
Long form
Effect
-c
-color
Colorize output (state/scope highlighted)
-br
-brief
One tidy aligned line per entry (the columnar view)
-r
-resolve
Reverse-DNS resolve addresses
-j
-json
Machine-readable JSON (pipe to jq)
-p
-pretty
Pretty-print (pair with -j)
-s
-stats
Include statistics (repeat -s -s for more)
-4 / -6
Restrict to IPv4 / IPv6 only
# The compact colorized address table (memorable as the `ipa` shortcut)
ip -color -brief -resolve addr # short: ip -c -br -r a# Same treatment on other objects
ip -c -br link# interfaces: state + MAC, one line each
ip -c -br neigh # neighbor cache, columnar
ip -c route # colorized routing table
Every ip object accepts unambiguous abbreviations: ip a, ip l, ip r,
ip n, ip ru (rule), ip m (maddr).
Read-Only Inspection
Addresses & Links
ip -br a # addresses, one line per interface
ip -br a show up # only interfaces that are UP (filters noise)
ip -4 -br a # IPv4 only
ip a show eth0 # full detail for one interface
ip -br link# L2 view: state, MAC, MTU — no IPs
ip link show eth0 # one interface's link details
Routing
ip route # full routing table
ip route get 1.1.1.1 # WHICH route/interface a destination uses
ip route get 1.1.1.1 from 10.0.0.5 # source-based route selection
ip -6 route # IPv6 routing table
ip route show table all # every routing table (policy routing)
ip route get answers "why is this traffic leaving the wrong interface?" — it
reports the exact route, source address, and egress device the kernel picks.
Neighbors (ARP/NDP)
ip neigh # ARP (v4) + NDP (v6) cache
ip -br neigh # columnar
ip neigh show dev eth0 # neighbors on one interface
ip -s link# RX/TX bytes, packets, errors, drops per interface
ip -s -s link show eth0 # extended error breakdown for one interface
First stop for "is this NIC dropping packets?" — check the errors/dropped
columns.
JSON + jq Scripting — the Real Reason to Learn ip
ip -j emits structured JSON, so scripts parse fields reliably instead of
scraping ifconfig text that varies across versions.
# Pretty-printed full address dump
ip -j -p addr
# All IPv4 addresses on the host, one per line
ip -j addr | jq -r '.[].addr_info[] | select(.family=="inet") | .local'# Primary IP of a specific interface
ip -j addr show eth0 | jq -r '.[0].addr_info[] | select(.family=="inet") | .local'# Interfaces that are operationally UP
ip -j link | jq -r '.[] | select(.operstate=="UP") | .ifname'# Default gateway
ip -j route | jq -r '.[] | select(.dst=="default") | .gateway'# Neighbor cache as ip→mac pairs
ip -j neigh | jq -r '.[] | "\(.dst)\t\(.lladdr // "-")\t\(.state[0])"'
Watching Changes Live
ip monitor # stream ALL link/addr/route/neigh changes
ip monitor link# just interface up/down events
ip monitor address # address add/remove (watch DHCP renewals)
ip monitor route # routing table changes
ip monitor is invaluable for catching a flapping interface, a DHCP lease
renewal, or a VPN altering routes — it prints events as they happen.
Modern Subsystems net-tools Never Covered
ip rule # policy routing rules (which table applies to what)
ip route show table 100 # a specific non-main routing table
ip netns list # network namespaces (the base under containers)
ip netns exec <ns> ip -br a # run any command inside a namespace
ip -br link show type vlan # VLAN interfaces
ip -d link show <dev> # -d = driver/type detail (bond, bridge, vxlan…)
bridge -c fdb show # bridge forwarding DB (iproute2 bridge tool)
bridge vlan show # per-port VLAN membership on a bridge
Mutating Commands (require root)
These change live network configuration and are not persistent — they
vanish on reboot unless written into the distro's network config
(netplan/NetworkManager/systemd-networkd). Flagged here so they're
recognizable; run deliberately.
Addresses
sudo ip addr add 10.0.0.5/24 dev eth0 # assign an addresssudo ip addr add 10.0.0.5/24 dev eth0 label eth0:1 # labeled aliassudo ip addr del 10.0.0.5/24 dev eth0 # remove an addresssudo ip addr flush dev eth0 # remove ALL addresses on eth0
Links
sudo ip linkset eth0 up # bring interface upsudo ip linkset eth0 down # bring interface downsudo ip linkset eth0 mtu 9000 # set MTU (jumbo frames)sudo ip linkset eth0 address 02:11:22:33:44:55 # override MACsudo ip link add veth0 type veth peer name veth1 # create a veth pairsudo ip link delete veth0 # delete an interface
Routes
sudo ip route add 192.168.5.0/24 via 10.0.0.1 # add a routesudo ip route add default via 10.0.0.1 dev eth0 # set default gatewaysudo ip route add 10.1.0.0/16 dev eth0 metric 100 # metric-weighted routesudo ip route del 192.168.5.0/24 # remove a routesudo ip route replace default via 10.0.0.254 # atomically swap default
Neighbors
sudo ip neigh add 10.0.0.9 lladdr 00:11:22:33:44:55 dev eth0 nud permanent # static ARPsudo ip neigh del 10.0.0.9 dev eth0 # drop a neighbor entrysudo ip neigh flush dev eth0 # clear the cache on eth0
Common Patterns
What's my IP and gateway?
ip -br a show up # human view
ip -j route | jq -r '.[] | select(.dst=="default") | .gateway'# gateway only
Why is traffic taking the wrong path?
ip route get <dest-ip> # exact route + source + egress interface
ip rule # is a policy rule diverting it to another table?
ip route show table <n> # inspect that table
Is this interface dropping packets?
ip -s link show <dev> # check errors / dropped counters
watch -n 1 'ip -s link show <dev> | grep -A1 RX'# watch them climb
Namespace-aware inspection (containers)
for ns in $(ip netns list | awk '{print $1}'); doecho"== $ns =="; ip netns exec"$ns" ip -br a
done
