Networking

Reconstruct an HTTPS flow across the TCP/IP stack, route incident snapshots to the right OSI layer, read a saved tcpdump capture of a TCP handshake, and run a layer-by-layer triage drill from captured incident artifacts.

Audit and remediate a real Linux ops stack: inspect iptables rules, diagnose AWS Security Group vs NACL behavior, choose SSH hardening fixes, interpret fail2ban jail status against auth.log, and diagnose an iptables rule-ordering bug that lets abuse traffic through.

Pick the smallest free CIDR from IPAM capacity data, reject a public VPC proposal, verify a four-subnet plan against allocation records, and catch an overlapping CIDR before it breaks peering.

Walk a saved dig +trace through the resolution chain, audit a zone file by record type, compare two dig outputs to spot a stale answer, and trace a stale-deploy outage to the missing TTL drop.

An incident-triage companion to the HTTP & TLS article: compare response headers, analyze curl captures, audit certificate-chain details, and classify the HTTP/TLS failures you'll actually hit on call.

An on-call companion to the Nginx article: tour a real /etc/nginx/ tree, debug a SPA deep-link 404, fix a proxy_pass path bug, audit a load-balancer skew, and unblock a failed deploy.