network-engineering

# Network Engineering Comprehensive network engineering skill covering network design, troubleshooting, load balancing, DNS, and network security. ## When to Use This Skill - Designing network topologies - Troubleshooting connectivity issues - Configuring load balancers - DNS configuration and troubleshooting - SSL/TLS setup and debugging - Network security implementation - Performance optimization - CDN configuration ## Network Architecture ### OSI Model Reference | Layer | Name | Protocols | Troubleshooting | |-------|------|-----------|-----------------| | 7 | Application | HTTP, DNS, SMTP | curl, browser tools | | 6 | Presentation | SSL/TLS | openssl | | 5 | Session | NetBIOS | - | | 4 | Transport | TCP, UDP | netstat, ss | | 3 | Network | IP, ICMP | ping, traceroute | | 2 | Data Link | Ethernet | arp | | 1 | Physical | - | cable tester | ### VPC/Network Design **Subnet Strategy:** ``` VPC CIDR: 10.0.0.0/16 (65,536 IPs) Public Subnets (internet-facing): - 10.0.1.0/24 (AZ-a) - Load balancers, bastion - 10.0.2.0/24 (AZ-b) - 10.0.3.0/24 (AZ-c) Private Subnets (application tier): - 10.0.11.0/24 (AZ-a) - App servers - 10.0.12.0/24 (AZ-b) - 10.0.13.0/24 (AZ-c) Database Subnets (isolated): - 10.0.21.0/24 (AZ-a) - Databases only - 10.0.22.0/24 (AZ-b) - 10.0.23.0/24 (AZ-c) ``` **Traffic Flow:** - Internet → Load Balancer (public) → App (private) → DB (isolated) - NAT Gateway for private subnet outbound - VPC Endpoints for AWS services ## Load Balan...