Linux Networking Commands

linux_networking.sh

# View device IP Address(es)
ip -o address show [interface] | awk '{print $4}' # Prints the IP address(es) of a single interface
ip address # Displays all interfaces
ifconfig # (deprecated)
hostname -I # Displays only IP addresses

# DNS name and resolution
host
dig
/etc/hosts # Add manual DNS record to hostname mappings (normally checked before configured DNS server(s))
/etc/nsswitch.conf # Can be used to change the order of lookups

# View device hostname
hostname
hostname -f
uname -n

# View routing table ( -n skips DNS resolution )
    # Using route
    route -n
    # Using ip
    ip route show
    
# Add/Delete static routes
    # Using route
    sudo route add -net 192.168.2.0/24 dev eth3
    sudo route del -net 192.168.2.0/24 dev eth3
    # Using ip
    sudo ip route add 192.168.2.0/24 dev eth3
    sudo ip route del 192.168.2.0/24 dev eth3

# Add/Delete Default Gateway
    # Using route
    sudo route add default gw 192.168.0.1
    sudo route del default gw 192.168.0.1
    # Using ip
    sudo ip route add default via 192.168.0.1
    sudo ip route del default via 192.168.0.1

# Configure or remove interface with IP Address, Subnet Mask, and Broadcast Address
    # Using ifconfig
    sudo ifconfig eth0 192.168.0.100 netmask 255.255.255.0 broadcast 192.168.0.255
    # Using ip
    sudo ip addr add 192.168.0.100/24 broadcast 192.168.0.255 dev eth0
    sudo ip addr del 192.168.0.100/24 dev eth0

# Enable/Disable interface
    # Using ifconfig
    sudo ifconfig eth0 up
    sudo ifconfig eth0 down
    # Using ifup/ifdown
    sudo ifup eth0
    sudo ifdown eth0
    # Using ip
    sudo ip link set eth0 up
    sudo ip link set eth0 down
    

# Modify Maximum Transfer Unit (MTU) on an interface (default: 1500 bytes)
sudo ifconfig eth0 mtu 1496

# Add static interface configuration in /etc/dhcpcd.conf
interface eth0
    static ip_address=192.168.0.100/24
    static routers=192.168.0.1
    static domain_name_servers=192.168.0.1
    
# Add static interface configurations in /etc/network/interfaces
iface eth0 inet static
    address 10.0.0.41
    netmask 255.255.255.0
    network 10.0.0.0
    broadcast 10.0.0.255
    gateway 10.0.0.1
    dns-nameservers 10.0.0.1 8.8.8.8
    dns-domain acme.com
    dns-search acme.com
    
# Validate /etc/network/interfaces configuration
ifquery --list # Displays available interfaces
ifquery [interface]
    
# Restart networking service
sudo /etc/init.d/networking restart