Let’s do some network! YAY!

Network cards and MACs

List interfaces

root@my-server:~# ip link show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN mode DEFAULT group default qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP mode DEFAULT group default qlen 1000
    link/ether 0c:c4:7b:84:5f:2e brd ff:ff:ff:ff:ff:ff
3: eno2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN mode DEFAULT group default qlen 1000
    link/ether 0c:c4:7b:84:5f:3e brd ff:ff:ff:ff:ff:ff

Start an interface

ip link set eno1 up

Change a MAC address

ip link set eno1 address 00:11:22:33:44:55

Network cards and IPs

List IPs

root@my-server:~# ip address show
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
    inet6 ::1/128 scope host
       valid_lft forever preferred_lft forever
2: eno1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc mq state UP group default qlen 1000
    link/ether 0c:c4:7b:84:5f:2e brd ff:ff:ff:ff:ff:ff
    inet 163.172.67.112/24 brd 163.172.67.255 scope global eno1
       valid_lft forever preferred_lft forever
    inet6 fe80::ec4:7aff:fe84:5d3e/64 scope link
       valid_lft forever preferred_lft forever
3: eno2: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
    link/ether 0c:c4:7b:84:5f:3e brd ff:ff:ff:ff:ff:ff

Add an IP

ip address add dev eno2 192.168.0.42/24

Remove an IP

ip address del dev eno2 192.168.0.42/24

Network cards and IPs

List neighbours

root@my-server:~# ip neighbour show |tail -n20
163.172.67.239 dev eno1 lladdr 0c:c4:7a:84:5f:88 STALE
163.172.67.157 dev eno1 lladdr 0c:c4:7a:84:5f:78 STALE
163.172.67.8 dev eno1 lladdr 0c:c4:7a:84:5f:36 STALE
163.172.67.167 dev eno1 lladdr 0c:c4:7a:84:5d:cc STALE
163.172.67.91 dev eno1 lladdr 0c:c4:7a:84:7f:f6 STALE
163.172.67.192 dev eno1 lladdr 0c:c4:7a:84:5f:9e STALE
163.172.67.246 dev eno1 lladdr 0c:c4:7a:84:7c:b0 STALE
163.172.67.73 dev eno1 lladdr 0c:c4:7a:84:5c:cc STALE
163.172.67.127 dev eno1 lladdr 0c:c4:7a:84:7d:da STALE
163.172.67.152 dev eno1 lladdr 0c:c4:7a:84:7e:30 STALE
163.172.67.142 dev eno1 lladdr 0c:c4:7a:84:5d:2a STALE
163.172.67.1 dev eno1 lladdr 58:ac:78:b1:1d:cd DELAY
163.172.67.162 dev eno1 lladdr 0c:c4:7a:84:5d:8e STALE
163.172.67.80 dev eno1 lladdr 0c:c4:7a:84:7c:f0 STALE
163.172.67.207 dev eno1 lladdr 0c:c4:7a:84:7d:46 STALE
163.172.67.253 dev eno1 lladdr 0c:c4:7a:84:5d:c8 STALE
163.172.67.104 dev eno1 lladdr 0c:c4:7a:84:7e:90 STALE
163.172.67.30 dev eno1 lladdr 0c:c4:7a:84:61:0e STALE
163.172.67.145 dev eno1 lladdr 0c:c4:7a:84:5d:3c STALE

Delete neighbour entry

ip neighbour del 163.172.67.253 dev eno1

Network cards and routes

List routes

root@my-server:~# ip route show
default via 163.172.67.1 dev eno1
163.172.67.0/24 dev eno1 proto kernel scope link src 163.172.67.112

Add route

ip route add 192.168.0.0/24 dev eno2
ip route add 192.168.100.0/24 via 192.168.0.1
ip route add default via 192.168.0.254

Remove route

ip route del 192.168.100.0/24

Network cards and persistence

(Under Debian-based operating systems)

network-manager

  • a helper for beginners
  • will mostly conflict with our objectives
  • not on any production grade server

networking

/etc/network/interfaces

source /etc/network/interfaces.d/*

auto lo
iface lo inet loopback

/etc/network/interfaces/eno1

allow-hotplug eno1
iface eno1 inet dhcp

/etc/network/interfaces/eno2

allow-hotplug eno1
iface eno1 inet static
  address 192.168.0.10
  netmask 255.255.255.0
  gateway 192.168.0.254

Resolving domains

Configuration file available in /etc/resolv.conf

root@my-server:~# cat /etc/resolv.conf
nameserver 62.210.16.6
nameserver 62.210.16.7