Networking Skill
Overview
Master networking fundamentals for DevOps infrastructure management.
Parameters
| Name | Type | Required | Default | Description |
|---|---|---|---|---|
| protocol | string | No | all | Protocol focus |
| operation | string | Yes | - | Operation type |
Core Topics
MANDATORY
- •TCP/IP and OSI model
- •DNS configuration and troubleshooting
- •HTTP/HTTPS and TLS
- •SSH key management and tunneling
- •Firewall basics (iptables, ufw)
OPTIONAL
- •Load balancing
- •VPN and tunneling
- •Traffic analysis with tcpdump
ADVANCED
- •BGP and routing protocols
- •SDN concepts
- •Zero-trust networking
Quick Reference
bash
# DNS dig +trace example.com dig @8.8.8.8 example.com host -t MX example.com # TCP/IP Diagnostics ping -c 4 host traceroute host ss -tuln ip addr show # HTTP Testing curl -I https://example.com curl -v https://example.com # SSL/TLS openssl s_client -connect host:443 openssl x509 -in cert.pem -text -noout # SSH ssh-keygen -t ed25519 ssh-copy-id user@host ssh -L 8080:localhost:80 user@host ssh -D 1080 user@host # Firewall (UFW) ufw status verbose ufw allow 22/tcp ufw deny from 192.168.1.100 # Firewall (iptables) iptables -L -n -v iptables -A INPUT -p tcp --dport 22 -j ACCEPT
Troubleshooting
Common Failures
| Symptom | Root Cause | Solution |
|---|---|---|
| Connection refused | Service not running | Check ss -tuln |
| Connection timeout | Firewall/routing | Check firewall, traceroute |
| Name resolution failed | DNS issue | Check /etc/resolv.conf |
| Certificate error | Expired/invalid cert | Check dates, verify chain |
Debug Checklist
- •Layer 1-2: Link up?
ip link show - •Layer 3: Ping gateway?
- •Layer 4: Port open?
ss -tuln - •DNS: Resolving?
dig hostname - •Firewall: Allowing?
iptables -L
Recovery Procedures
Lost SSH Access
- •Use cloud console/IPMI
- •Check sshd:
sshd -t - •Verify firewall:
iptables -L -n