Networking basics.
On a modern RHEL system, NetworkManager owns the network and nmcli is how you drive it. Watch an interface go from no address to a fully configured static IP — connection profile, gateway, DNS — then verify it end to end.
Linux networking basics animated tutorial. Interfaces and IP addresses, NetworkManager connections vs devices, configuring a static IP with nmcli, the default gateway and DNS, connection profiles, and verification with ip/ping/nmcli. RHCSA EX200 ready.On RHEL, NetworkManager owns the network and nmcli drives it. Watch an interface go from no address to a fully configured, persistent static IP — then verify the whole chain.
- ·Know what an IP address and CIDR (/24) mean
- ·Helpful: the NAT-and-routing lesson (gateways, routes)
- ·Comfortable running commands as root / with sudo
Configure a static IP with nmcli, understand connections vs devices, set the gateway and DNS, and troubleshoot connectivity layer by layer.
pace: 10 minutes
deviceens160MAC00:0c:29:ab:cd:efInterfaces and addresses
A network interface is the kernel's handle on a NIC — named like ens160, eth0, or wlan0 (lo is the loopback). `ip addr` shows each interface, its state (UP/DOWN), and its IP address with CIDR prefix (e.g. 192.168.1.50/24 — the /24 means the first 24 bits are the network). A fresh interface may be UP at the link layer but have no IP yet.
$ip addr$ip -br addr$ip linkThe mental model: edit the profile, then activate it. `nmcli con mod` writes settings to disk; `nmcli con up` applies them. Forgetting the second step is the #1 "I changed it but nothing happened" confusion. And never hand-edit /etc/resolv.conf — NetworkManager owns it.
$nmcli dev status$nmcli con show$nmcli con show ens160$nmcli con add type ethernet con-name ens160 ifname ens160$nmcli con mod ens160 ipv4.addresses 192.168.1.50/24$nmcli con mod ens160 ipv4.gateway 192.168.1.1$nmcli con mod ens160 ipv4.dns 1.1.1.1$nmcli con mod ens160 ipv4.method manual$nmcli con up / down ens160$nmcli con reload$ip addr / ip -br a$ip route$ping -c3 HOST$ss -tlnp$hostnamectl set-hostname X$/etc/NetworkManager/system-connections/In NetworkManager terms, what's the difference between a 'device' and a 'connection'?
You ran `nmcli con mod ens160 ipv4.addresses 192.168.1.50/24 ipv4.method manual` but the interface still has its old DHCP address. Why?
`ping 1.1.1.1` works but `ping google.com` fails. What's broken?
Where should you set the DNS servers on a NetworkManager system, and what should you NOT do?
These aren't graded — they're just for active recall, which is what actually makes the lesson stick.
subnet calculator
Before you assign 192.168.1.50/24, know exactly which addresses are on-subnet, where the gateway and broadcast sit, and how many hosts fit.
keep going — these pair well with what you just learned.
What happens when you type a URL?
The most-asked interview question, animated. Five chapters: DNS → TCP → TLS → HTTP → Render. Step through each at your own pace.
OSI / TCP-IP layers
A packet wrapped layer-by-layer, then unwrapped on the other side. Watch headers stack and peel off — OSI 7 and TCP/IP 4 side by side.
DNS deep dive
Beyond the basics: recursive vs iterative, cache layers, TTLs, glue records, and what `dig +trace` actually shows.