🚀 DevOps Networking Cheat Sheet

1️⃣ Networking Basics

• IP Addressing: Unique device identifier on a network
• IPv4: 192.168.1.1/24
• IPv6: 2001:db8::1/64
• Subnet Mask: Divides network & host portion
• Gateway: Device connecting your network to outside networks
• DNS: Converts domain names to IP addresses

Quick Commands:

ifconfig / ip addr # Show network interfaces

ping <IP/hostname> # Check connectivity

traceroute <IP/hostname> # Trace path to destination

nslookup <domain> # DNS lookup

dig <domain> # Advanced DNS lookup

2️⃣ Common Protocols

ProtocolPortUseHTTP80Web trafficHTTPS443Secure web trafficSSH22Secure remote accessFTP21File transferSFTP22Secure file transferSMTP25Sending emailIMAP143Email retrievalDNS53Domain name resolutionDHCP67/68IP assignment

3️⃣ Routing & Firewalls

• Routing: Directs packets between networks
• Default Route: 0.0.0.0/0 points to gateway
• NAT (Network Address Translation): Private → Public IP
• Firewall: Filters traffic based on rules

Linux Firewall (iptables / ufw) Example:

ufw status

ufw allow 22/tcp # Allow SSH

ufw deny 80/tcp # Block HTTP

4️⃣ DNS / Load Balancing

• DNS Records:
• A → IPv4
• AAAA → IPv6
• CNAME → Alias
• MX → Mail
• Load Balancer:
• Distributes traffic to multiple servers
• Types: Round Robin, Least Connections, IP Hash

Nginx Load Balancer Example:

upstream backend {

server 192.168.1.2;

server 192.168.1.3;

}

server {

listen 80;

location / {

proxy_pass http://backend;

}

}

5️⃣ Common DevOps Networking Tools

• ping / traceroute / nslookup / dig – basic network testing
• netstat / ss – check open ports & connections
• tcpdump / Wireshark – packet capture
• curl / wget – HTTP requests
• telnet / nc (netcat) – port testing

6️⃣ Docker & Kubernetes Networking

• Docker Bridge Network: Containers communicate internally
• Host Network: Container shares host network
• Overlay Network: Multi-host container networking (Swarm/K8s)
• K8s Services:
• ClusterIP → internal
• NodePort → external access
• LoadBalancer → cloud LB
• Ingress → HTTP routing & SSL termination

Kubernetes Example:

apiVersion: v1

kind: Service

metadata:

name: my-service

spec:

type: NodePort

selector:

app: my-app

ports:

- protocol: TCP

port: 80

nodePort: 30001

7️⃣ SSH & Remote Access

ssh user@server-ip # Connect to server

ssh -i key.pem user@server # Key-based authentication

scp file.txt user@server:/path # Copy file via SSH