IT & Network Engineering Technical Guides

Hierarchical IP addressing standards, zero-waste VLSM block subnetting, and wildcard mask calculation rules for access lists and dynamic routing protocols (OSPF/EIGRP).

• /24 = 256 Total IPs, 254 Usable Hosts (Netmask 255.255.255.0, Wildcard 0.0.0.255)
• /26 = 64 Total IPs, 62 Usable Hosts (Netmask 255.255.255.192, Wildcard 0.0.0.63)
• /29 = 8 Total IPs, 6 Usable Hosts for Public DMZ (Netmask 255.255.255.248, Wildcard 0.0.0.7)
• /30 = 4 Total IPs, 2 Usable Hosts for Router PTP WAN (Netmask 255.255.255.252, Wildcard 0.0.0.3)
• /32 = 1 Single Host for Loopback Interface (Netmask 255.255.255.255, Wildcard 0.0.0.0)

Per-connection classifier (PCC) mechanics with both-addresses-and-ports hashing, RouterOS v7 FIB routing tables, and recursive next-hop gateway monitoring.

• Deploy 'both-addresses-and-ports' hashing for uniform HTTPS packet flow without invalidating banking TLS sessions.
• Assign connection marks in prerouting chain before committing routing marks.
• In RouterOS v7, declare custom tables explicitly via /routing table add name=to-WANx fib.
• Recursive failover binds virtual next-hops to public resolvers (8.8.8.8) with target-scope=30 for zero-loss path fault detection.

Optical Distribution Network (ODN) budget sizing across Class B+ (+28 dB) and Class C+ (+32 dB), theoretical PLC splitter insertion loss (1:2 to 1:64), and ONT Rx thresholds.

• Normative PLC Splitter Loss: 1:2 ~3.5 dB, 1:4 ~7.2 dB, 1:8 ~10.5 dB, 1:16 ~13.8 dB, 1:32 ~17.1 dB, 1:64 ~20.5 dB.
• Single-mode fiber loss: 0.35 dB/km @ 1310nm and 0.22 dB/km @ 1490/1550nm.
• Target ONT Rx optical sensitivity window: -15 dBm to -24 dBm (Receiver saturation > -8 dBm, LOS threshold < -27 dBm).
• Cascade topologies: Deploy asymmetrical PLC taps (80:20 or 70:30) to preserve optical link budget across pole trunks.

Usable storage capacity engineering for ZFS pools, 80% Copy-on-Write threshold safety, ARC memory requirements, dual parity trade-offs, and Proxmox VE VM sizing.

• ZFS Copy-on-Write (CoW) experiences severe write performance degradation and fragmentation once pool capacity exceeds 80%.
• RAIDZ2 dual-parity is mandatory for enterprise HDDs >= 8TB due to multi-day resilver windows and secondary drive failure risk.
• ZFS ARC memory sizing rule-of-thumb: 1 GB ECC RAM per 1 TB usable storage + 8 GB base OS allocation.
• Dedicated SLOG vdevs require Enterprise NVMe drives featuring Power Loss Protection (PLP) for sync database workloads.

Formulas for 30-day NVR storage sizing, H.265+ smart compression efficiency, and Cat5e/Cat6 loop resistance voltage drop limits preventing remote camera reboots.

• 1080p @ 25fps on H.265+ requires an average of 1.5 to 2 Mbps per channel (saving ~50% storage footprint vs legacy H.264).
• 4K (8MP) sensors require 6 to 8 Mbps per channel for definitive nighttime facial and license plate recognition.
• PoE Standards: 802.3af (15.4W PSE / 12.95W PD), 802.3at PoE+ (30W PSE / 25.5W PD), 802.3bt Type 4 (90W PSE / 71W PD).
• Cat6 pure solid copper cable voltage drop must remain below 4.5V over maximum 90-meter structured runs.

Best practices for Linux privilege boundary hardening (chmod/chown), Docker Compose orchestration behind Nginx reverse proxy, and Little's Law API concurrency sizing.

• Private SSH keys require strict chmod 600 (-rw-------), while the parent ~/.ssh directory requires chmod 700 (drwx------).
• Production sshd_config must enforce PasswordAuthentication no and PermitRootLogin prohibit-password.
• Run Docker containers with non-root UID boundaries and tune host kernel swappiness to 10 for memory latency stability.
• API Sizing: If an endpoint serves 1,000 RPS with 50ms average latency (0.05s), the backend requires at least 50 concurrent worker threads.