Lesson 1.3: IP Addresses and Port Management

IP Address Fundamentals

Private IP Ranges (RFC 1918)

These ranges are reserved for private networks:

• Class A: 10.0.0.0/8 (10.0.0.0 - 10.255.255.255)
• Class B: 172.16.0.0/12 (172.16.0.0 - 172.31.255.255)
• Class C: 192.168.0.0/16 (192.168.0.0 - 192.168.255.255)

Localhost and Loopback

• 127.0.0.1: IPv4 loopback (localhost)
• ::1: IPv6 loopback
• 0.0.0.0: All interfaces (bind to all IPs)

Port Management Strategy

Well-Known Ports (0-1023)

Reserved for system services:

• 22: SSH
• 53: DNS
• 80: HTTP
• 443: HTTPS

MCT Services Port Allocation

Our current port strategy:

# Core Services
80/443    - Traefik (Reverse Proxy)
53        - Pi-hole (DNS)

# Application Services  
8080      - Nextcloud
8081      - Stash
8082      - MeTube
8083      - Dashy
8084      - Keycloak
8085      - Moodle

# Database Services
3306      - MariaDB
5432      - PostgreSQL
6379      - Redis

# Monitoring
9090      - Prometheus
3000      - Grafana

Port Conflict Resolution

Common strategies for avoiding conflicts:

1. Port Mapping: Use Docker port mapping
2. Reverse Proxy: Single entry point (port 80/443)
3. Port Ranges: Allocate ranges by service type
4. Documentation: Maintain port registry

Docker Port Management

Docker Compose port mapping examples:

services:
  nextcloud:
    ports:
      - 8080:80    # Host:Container
  
  traefik:
    ports:
      - 80:80      # HTTP
      - 443:443    # HTTPS
      - 8080:8080  # Dashboard

Network Interface Binding

Control which interfaces services bind to:

# Bind to localhost only
127.0.0.1:8080:80

# Bind to specific interface
192.168.1.100:8080:80

# Bind to all interfaces
0.0.0.0:8080:80

Firewall Considerations

Essential firewall rules for personal cloud:

# Allow HTTP/HTTPS
sudo ufw allow 80/tcp
sudo ufw allow 443/tcp

# Allow SSH (if needed)
sudo ufw allow 22/tcp

# Allow specific application ports
sudo ufw allow 8080:8090/tcp

Practical Exercise

Task: Design your port allocation strategy

1. Audit current port usage: netstat -tulpn
2. Design port allocation scheme
3. Document port assignments
4. Test port availability
5. Configure firewall rules

Troubleshooting Tools

# Check port usage
netstat -tulpn | grep :8080
ss -tulpn | grep :8080

# Test port connectivity
telnet localhost 8080
nc -zv localhost 8080

# Check which process uses a port
lsof -i :8080