Interfaces

Interfaces#

Network interfaces are the kernel’s view of every NIC, virtual link, bridge, tunnel, and loopback. ip is the modern tool for inspecting and reconfiguring them; the old ifconfig is deprecated but still shows up in legacy scripts.

The list of interface kinds an operator meets in the wild. Each shows up in ip link with its own type, state machine, and quirks; mixing them up in firewall rules is a frequent source of “why isn’t this working” tickets.

Name

Kind

Notes

lo

loopback

127.0.0.1 / ::1

ethN

physical NIC

UP / DOWN / NO-CARRIER

wlanN

wireless

SSID, association state

brN

software bridge

L2 switch (br0 + eth0 + tap0 ...)

bondN

link aggregation

N NICs as one (LACP, active-backup)

vlanN

802.1Q tag

eth0.10 = VLAN 10 on eth0

vethX-vethY

pair

one half in netns, one in host

tunN / tapN

userspace tunnel

L3 (tun) / L2 (tap)

wgN

WireGuard

encrypted L3

docker0, cni*

container nets

bridge or veth into namespaces

Bring-up sequence; each step gates the next:

        flowchart LR
  U[link UP] --> C{carrier?} --> A{addr assigned?} --> R{route present?} --> Y[usable]
    
operator@system:~$ ip addr
operator@system:~$ ip a show eth0
operator@system:~$ ip link set eth0 up
operator@system:~$ ip link set eth0 down

operator@system:~$ ip addr add 192.168.1.10/24 dev eth0
operator@system:~$ ip addr del 192.168.1.10/24 dev eth0