Network Redundancy Planning

🏢 Enterprise Dual ISP Internet Edge Design — What Production-Grade Redundancy Actually Looks Like Single ISP = single point of failure. In enterprise networking, that's simply not acceptable. Here's a breakdown of this High-Level Design (HLD) built for maximum resilience: ☁️ ISP Layer — Dual Provider Redundancy → Two completely separate ISPs (ISP-1 & ISP-2) → Each connects via eBGP on Gi0/0 — no shared fate 🌐 WAN Edge — BGP Traffic Engineering → Edge Router A & B peer with their respective ISPs via eBGP → Inter-router iBGP link enables coordinated routing decisions → BGP attributes used: Local Preference, AS-Path, MED → ECMP optionally enabled for load balancing across both ISPs 🔥 Security Layer — Firewall HA Pair → Active/Standby firewalls connected via State Sync Link → Session state is mirrored — failover is seamless, zero session drops → Connected to edge routers via Port-Channel (Po1) for link aggregation 🔐 Security Trust Boundary + NAT → Clear demarcation between untrusted (internet) and trusted (internal) zones → NAT boundary sits here — public-to-private translation handled at this layer 🔀 Core Layer — VSS/vPC Redundancy → Core Switch A & B connected via Peer Link (Po10) → OSPF runs as the IGP between Core and Distribution → Dual uplinks to both distribution switches (cross-connected for full redundancy) 📡 Distribution Layer — OSPF IGP → Dist-1 & Dist-2 interconnected via Po3 running OSPF → Each dist switch dual-homes to both core switches 🖥️ Access Layer → User VLANs → Access switches connect to both distribution switches via Po200 → Traffic segregated into: User VLANs | Server VLANs | Printer VLAN 💡 Why this design wins: ✅ No single point of failure from ISP to end user ✅ BGP gives granular traffic control & fast failover ✅ Firewall HA ensures security without sacrificing uptime ✅ OSPF provides fast IGP convergence internally ✅ Port-Channels eliminate individual link failures This is the blueprint enterprises use to achieve 99.99%+ uptime at the internet edge. Are you running dual ISP in your environment? What's your BGP failover strategy? 💬 #NetworkEngineering #EnterpriseNetworking #BGP #OSPF #NetworkDesign #HighAvailability #DataCenter #CiscoNetworking #NetworkArchitecture #CCNP #Infrastructure #Redundancy #NetworkSecurity #ITInfrastructure

95% of the world’s internet traffic moves through subsea cables. Not satellites. Not clouds. Just glass. Laid on ocean floors. Invisible. Critical. Exposed. This year, four major cables in the Red Sea were cut... ...and Asia-Europe lost 25% of bandwidth. And no, it wasn’t an war. Just anchors. Fishing nets. Seabed tectonics. If your DR plan doesn’t include the ocean floor... ...you’re not ready. Here’s how to build real resilience... ...with SubCom as your on-ground truthful partner: ✧ MAP Trace your traffic flows. Which systems carry your core paths? SEA-ME-WE 6? AAE-1? EIG? Tag landing stations, handoffs, terrestrial hops. Now mirror that in your L3 overlays using SubCom’s telemetry. ✧ SPLIT Don’t load balance across two POPs… ...that land on the same cable. Use SubCom’s open cable design to mix routes, geographies, and owners. Redundancy ≠ resilience unless it spans tectonic and political zones. ✧ DESIGN SubCom supports wavelength-level reroute. Define fault domains. Automate handoff to your SD-WAN controller. No more manual ticket escalations at 2 AM. ✧ SIMULATE Run Red Team drills for dual cable cuts. Measure time-to-recovery. Not hope. Coordinate with SubCom’s NOC before the anchor drops. ✧ MONITOR SubCom gives you real-time fault zones, vessel paths, route degradation. Pipe it into your NOC. Pair it with your IXP metrics. Predict the cut before the outage. We stress over power and cooling redundancy in data centers. But one snapped fibre under water can drop an entire region. At 400G, there’s no retry logic. There’s signal. Or outage. Design accordingly. What’s your failover plan if the ocean goes dark? Tag your network team, this is the layer nobody’s watching.

I'm back in the lab today and I decided to add some resiliency through automation. Today’s focus in my E-University network project was simple: build redundancy where it matters and detect failures fast, with validation and visibility baked in from the start. Here's what I added today: HSRP deployment with pyATS validation: - I deployed HSRP gateway redundancy across three campus networks (Main, Medical, and Research) spanning six PE routers and 11 HSRP groups, with load balancing across the two edge routers per site. Instead of configuring first and hoping it worked, I wrote pyATS/Genie validation tests up front to define the expected end state, automated the deployment with Python and Unicon, and then re-ran the tests to prove compliance. That test-first approach paid off immediately. The pyATS checks caught an IP addressing mistake (10.300.x.x is not valid) before it could turn into a troubleshooting session. BFD for sub-second failure detection: I also implemented BFD on edge links (not inside the MPLS core) to dramatically improve convergence time versus relying on OSPF hello/dead timers. With 100ms interval, 100ms min-rx, and multiplier 3, detection is roughly 300ms, compared to an OSPF dead interval around 40 seconds. Observability integrated into the stack: This is all tied into my containerized telemetry pipeline: - A Python collector (Netmiko) polling 16 devices every 30 seconds. - InfluxDB 2.7 for time-series storage. - Grafana dashboards that now include protocol health and redundancy state, not just CPU/memory/interface counters. The Grafana view includes OSPF neighbor counts, BGP session state and prefix counts, BFD up/down session totals, and the HSRP active/standby state across all 11 groups. How I kept it clean (Git workflow): One thing I’ve been trying to do more of is treating my lab like real engineering work. For the Grafana updates, I created a separate Git branch specifically to test new dashboard panels and provisioning changes so I could iterate without breaking the main lab project. Once everything looked right, it’s easy to merge back in, and if something goes sideways I can roll it back without touching the stable baseline. Why this matters: Network automation is not just about pushing configs faster. It is about building confidence through validation. Writing tests first forces you to define success criteria upfront, and passing tests gives you proof that the change actually worked. #NetworkAutomation #NetDevOps #pyATS

This network design features a dual-infrastructure setup using two different firewall platforms, FortiGate and Palo Alto, to provide redundancy and segmentation. The design aims to ensure high availability and robust security for a network with critical assets, likely belonging to a mid to large-sized enterprise. The network is connected to two Internet Service Providers (ISPs) labeled ISP-A and ISP-B. The connections are managed through two switches (SW-15 and SW-16) on the FortiGate side, and two other switches (SW-19 and SW-110) on the Palo Alto side. These switches act as the primary and backup points of entry for the internet traffic, ensuring that if one ISP fails, the other can still provide connectivity. This setup provides resilience and fault tolerance. On the FortiGate side, two FortiGate firewalls are deployed in a high-availability (HA) configuration. This setup means that one firewall will take over if the other fails, providing uninterrupted security services. The firewalls are connected to layer 3 switches (L3-SW7 and L3-SW13) which manage internal routing and distribution of traffic. The layer 2 switches (L2-SW13) underneath connect to end devices or servers, shown as VPCs. This segmentation allows the internal network to be divided into different VLANs (VLAN 10, 21, 22, 23), each with its IP subnet, offering isolation and traffic management according to the organization’s requirements. Similarly, on the Palo Alto side, there are two firewalls, also configured in HA. They are connected to a layer 3 switch (L3-SW8) that performs a similar role in routing and distributing traffic. VLANs (30, 31, 32, 33) are used here as well, indicating that the network is segmented based on functions or departments. This helps in controlling and securing traffic flows, as well as in implementing policies such as access control lists (ACLs) or quality of service (QoS). The purpose of this design is twofold: to provide high availability and to ensure security and segmentation across the enterprise network. By using two different firewall platforms, the design can leverage the strengths of each while maintaining a diverse security posture, which is often recommended to avoid single points of failure or uniform vulnerabilities. The VLAN segmentation helps in managing and isolating traffic, ensuring that security policies can be applied more granularly. Additionally, the HA configurations on both the FortiGate and Palo Alto sides prevent downtime during hardware failures, contributing to the network's resilience. This setup offers a scalable, secure, and resilient architecture capable of supporting a range of enterprise applications and services while maintaining strict security controls and high availability.

⚡ What happens if a single fiber cable fails in a digital substation? Does protection stop working? Does communication collapse? Or does the system keep operating seamlessly? The answer depends on how well the communication network is designed. Modern substations rely heavily on IEC 61850 communication, where protection signals, GOOSE messages, and control commands travel through Ethernet networks. If communication fails at the wrong moment, the consequence could be delayed protection tripping or even equipment damage. That’s why redundancy protocols are critical in digital substations. 🔁 Here are 4 widely used redundancy protocols that keep substation communication reliable: 🔹 Dual Homing (Link Redundancy) One IED connects to two independent switches using two Ethernet ports. • Provides an alternate communication path • Simple and cost-effective architecture • Common in smaller substations or SCADA networks However, recovery time depends on switch configuration. 🔹 Rapid Spanning Tree Protocol (RSTP) RSTP prevents loops in ring networks while maintaining redundancy. • Network forms a ring topology • One link remains blocked during normal operation • If the active link fails → the blocked link activates automatically Typical recovery time: tens of milliseconds to a few seconds Suitable for general substation communication and SCADA systems. 🔹 Parallel Redundancy Protocol (PRP) PRP provides seamless zero-time redundancy. • Two completely independent networks (LAN A & LAN B) • Devices send duplicate frames simultaneously • The receiver processes the first frame and discards the duplicate ✔ Zero recovery time ✔ No packet loss That’s why PRP is widely used for critical protection communication and GOOSE messaging. 🔹 High-availability Seamless Redundancy (HSR) HSR achieves redundancy using a ring topology. • Frames are sent in both directions around the ring • The first arriving frame is accepted • If one path fails, communication continues instantly ✔ Zero switchover time ✔ Ideal for process bus and compact digital substations 💡 Not all redundancy solutions provide the same reliability. • Dual Homing → simple redundancy • RSTP → loop protection with backup path • PRP → zero-time recovery for critical protection • HSR → seamless redundancy in ring networks In protection systems, milliseconds matter. A well-designed redundancy architecture ensures that even if a cable fails, protection signals still reach the circuit breaker instantly. And in a digital substation, that can make all the difference between a safe trip and a costly failure. 🔁 If one communication link fails today in your substation… Will your protection signals still reach the breaker in time? ⚡ ♻️ Repost to share with your network if you find this useful 🔗 Follow Ashish Shorma Dipta for more posts like this #SubstationAutomation #IEC61850 #SmartGrid #PowerSystems #SCADA #Redundancy

For a large national corporation with a large number of locations and a third-party hosting location, ensuring the safest, fastest, and easiest network configuration for monitoring and operating various Building Automation Systems (BAS) and IoT systems involves a combination of modern networking technologies and best practices. Network Architecture, Centralized Management with Distributed Control, A robust core network at the third-party hosting location to manage central operations. Deploy edge devices at each location for local control and data aggregation. Use SD-WAN (Software-Defined Wide Area Network) to provide centralized management, policy control, and dynamic routing across all locations. SD-WAN enhances security, optimizes bandwidth, and improves connectivity. Ensure redundant internet connections at each location to avoid downtime. Failover Mechanisms: Implement failover mechanisms to switch to backup systems seamlessly during outages. VLANs and Subnets: Use VLANs and subnets to segregate BAS and IoT traffic from other corporate network traffic. Implement micro-segmentation to provide fine-grained security controls within the network. Next-Generation Firewalls (NGFW): Deploy NGFWs to protect against advanced threats. Intrusion Detection and Prevention Systems (IDPS): Implement IDPS to monitor and prevent malicious activities. Secure Remote Access, Use VPNs for secure remote access to the BAS and IoT systems. Zero Trust Network Access (ZTNA): Adopt ZTNA principles to ensure strict identity verification before granting access. Performance Optimization Traffic Prioritization: Use QoS policies to prioritize BAS and IoT traffic to ensure reliable and timely data transmission. Implement edge computing to process data locally and reduce latency. Aggregate data at the edge before sending it to the central location, reducing bandwidth usage. Ease of Management, Use a unified management platform to monitor and manage all network devices, BAS, and IoT systems from a single interface. Automate routine tasks and use orchestration tools to streamline network management. Design the network with scalability in mind to easily add new locations or devices. Integrate with cloud services for scalable data storage and processing. Recommended Technologies and Tools, Cisco Meraki for SD-WAN, security, and centralized management. Palo Alto Networks for advanced firewall and security solutions. AWS IoT or Azure IoT for cloud-based IoT management and edge computing capabilities. Dell EMC or HP Enterprise for robust server and storage solutions. Implementation Strategy, Conduct a thorough assessment of existing infrastructure and requirements. Develop a detailed network design and implementation plan. Implement a pilot at a few selected locations to test the configuration and performance. Gradually roll out the network configuration to all locations.

Systems don’t fail because something went wrong - they fail because nothing was prepared to handle what went wrong. That’s why failure-handling patterns are a core part of system design. This visual breaks down 12 essential techniques engineers use to build resilient, fault-tolerant systems that stay reliable under real-world pressure: - Retry Reattempt failed operations to handle temporary network or service glitches. Used in API calls, database queries, and distributed requests. - Circuit Breaker Stops calls to unhealthy services to prevent cascading failures. Common in microservices communication. - Bulkhead Isolates failures so one overloaded component doesn’t crash the entire system. Used with thread pools and microservice resource isolation. - Fallback Provides a degraded or cached response when a dependency fails. Keeps the user experience smooth with static data or defaults. - Timeouts Prevents waiting forever for slow or stuck services. Critical for APIs, databases, and distributed systems. - Dead Letter Queue (DLQ) Captures failed messages for later inspection or reprocessing. A staple in message queues and event-driven architectures. - Rate Limiting Protects systems from abuse or overload by restricting excessive requests. Used widely in public APIs and authentication services. - Load Shedding Drops non-critical traffic during peak load to keep core functions alive. Common in high-traffic or real-time systems. - Graceful Degradation Reduces functionality instead of failing completely. Used in dashboards, e-commerce platforms, and streaming apps. - Redundancy Duplicates critical components to eliminate single points of failure. Standard practice for databases, servers, and networks. - Health Checks Detects unhealthy services and removes them from rotation. Used by load balancers and orchestration tools. - Failover Automatically switches to a backup system when the primary one fails. Essential for multi-region deployments and database clusters. Mastering these techniques is what separates systems that work in theory from systems that work in production. Which ones have you used in your architecture?

Your network uses BGP every day. But is it designed for advanced traffic engineering, multi-cloud connectivity, and real-world resilience? BGP is deceptively complex. Small mistakes can cascade into major headaches. And when that happens, you need a BGP pro on your side. Here are some of the ways I can whisk your BGP problems away: 1️⃣ Internet Edge Multihoming & Traffic Engineering 👉 Inbound load-sharing: Shape how traffic enters your network using communities and AS-prepend, rather than leaving it to chance. 👉 ISP redundancy: Design your BGP architecture for multiple providers to ensure your network is protected against downtime. 👉 Leak & filter protection: Enforce max-prefix limits and implement robust route filtering to block unwanted traffic. 👉 Avoid asymmetrical routing: Influence outbound traffic through local-pref and other path selection mechanisms. 👉 Zero-impact maintenance: Use graceful shutdown so planned work doesn’t trigger unplanned outages. 2️⃣ Multi-Cloud Connectivity (including BGP over VPN) 👉 Consistent return paths: Eliminate asymmetric routing that causes performance issues. 👉 Stay inside provider limits: Aggregate prefixes to avoid hitting strict route caps. 👉 Clear path preference: Control MEDs and priorities so your cloud edges behave as intended. 👉 Fast, reliable failover: Tune timers and enable BFD for high-availability architectures you can trust. 3️⃣ DDoS Mitigation 👉 Instant blackholing (RTBH): Stop a DDoS attack by temporarily blackholing a prefix via the blackhole community. 👉 Flowspec deployment: Push precise filters upstream in real time, dropping only malicious flows instead of entire subnets. 4️⃣ Routing Security & Governance 👉 ROAs & RPKI validation: Prove your IP block ownership and prevent others from hijacking your prefixes. 👉 Clean IRR & AS-SETs: Keep your routing registry data accurate so peers and providers filter you correctly. 👉 End-to-end authentication: Enable MD5 authentication for BGP neighbors. The result: your network becomes predictable, resilient, and secure. That means peace of mind that your internet traffic won’t fail when the business depends on it the most. Quick checklist for network execs to evaluate BGP readiness: ✅Do we have max-prefix, “no-export/self” protections, and a graceful shutdown procedure with our ISPs/IXPs? ✅For each cloud edge, what’s our tested failover time and which prefixes/communities drive primary/backup? ✅Can we trigger RTBH/Flowspec in <1 minute, and with which upstreams? ✅Are all announced prefixes validated with ROAs, and are our IRR objects current? In which of these areas have you seen businesses struggle with their BGP designs? I'd love to hear your feedback in the comments below. 💬 #BGP #NetworkEngineering #CloudNetworking #DDoSProtection #RoutingSecurity #NetworkResilience #TechLeadership #MultiCloud #InternetEdge #NetworkOps

We often confuse High Availability (HA) with Disaster Recovery (DR). In a standard 3-Tier architecture, knowing the difference is what saves your job during a major outage. Let's break down the classic stack, where the Single Points of Failure (SPoF) hide, and how to build a DR strategy that actually works. 1️⃣ The "Standard" 3-Tier Context Most cloud-native apps follow this logical flow: Presentation Tier: The entry point (ALB, Nginx, React) handling user traffic. Application Tier: The business logic (EC2, Lambda, Python/Java) processing the requests. Data Tier: The source of truth (RDS, DynamoDB) storing the state. It looks clean on a whiteboard. But if you deploy this naively into a single Availability Zone (AZ), you are walking on thin ice. 2️⃣ Where the Single Points of Failure Hide Many teams think, "I have an Auto Scaling Group, so I'm safe." Wrong. Here is where the architecture breaks under pressure: 🚩 The Database (The obvious SPoF): A single RDS instance. If the hardware fails or patching hangs, your entire application stops. 🚩 The Network (The hidden SPoF): Relying on a single NAT Gateway for all private subnets. If that one gateway has an issue, your app servers lose connection to 3rd party APIs. 🚩The Region (The ultimate SPoF): Hosting everything in us-east-1 without a backup. If the region faces a service disruption (like S3 or IAM issues), no amount of local auto-scaling will save you. 3️⃣ The Solution: From Fragile to Anti-Fragile True resilience requires a two-pronged approach: Phase A: Local Resilience (High Availability) Multi-AZ Deployment: Spread your EC2s across at least 2 AZs. If one data center loses power, the other takes the load. Redundant Networking: Deploy a NAT Gateway in each AZ to ensure network isolation. Database Standby: Enable Multi-AZ for RDS. This creates a synchronous standby that fails over automatically in <60 seconds. Phase B: Regional Resilience (Disaster Recovery) This is where you graduate from "HA" to "DR." If the region goes dark, you need a plan. The Pilot Light Strategy: Replicate your data (RDS Read Replicas + S3 Replication) to a secondary region (e.g., us-west-2). Keep the compute resources "off" or minimal to save costs. DNS Failover: Use Route 53 to health-check your primary region. If it fails, flip the traffic to the secondary region. The Bottom Line: Resilience isn't just about keeping servers up; it's about assuming they will go down and designing the survival path. #AWS #SystemDesign #CloudArchitecture #DisasterRecovery #DevOps #Engineering

We over-engineer the silicon while neglecting the dirt. In enterprise IT we obsess over hardware. We buy N+1 core routers and tune them perfectly inside sanitized, climate-controlled fortresses. But outside those walls, we bet our entire network on two strands of fragile glass buried in the earth. We buy primary and backup circuits, audit the physical paths, and assume we're safe. Then a single backhoe severs both connections simultaneously, sending a "highly available" datacenter into a catastrophic Split-Brain meltdown. How? The "Silent Reroute." During routine maintenance, carriers frequently shuffle your perfectly separated physical links into the exact same high-capacity conduit to save OpEx. Your physical redundancy is quietly erased via civil engineering, and your Layer 3 controllers never flinch. When both paths die in the same trench, your datacenters lose their database Quorum majority. The isolated databases freeze to prevent data corruption, and your entire system violently halts. If you are running mission-critical interconnects, Dual-Homing isn't redundancy. It is a scheduled outage. To survive, Tri-Homing is the new minimum viable standard even if that third path is an IPsec tunnel or a Starlink connection. A backhoe can destroy a trench in seconds, but it cannot cut the sky. 🛰️ I wrote a breakdown on "The Backhoe Checkmate," the reality of the Silent Reroute, and how to build an architecture that actually survives. Read the full framework in the article below. 👇 #NetworkEngineering #HighAvailability #DataCenter #DisasterRecovery #EnterpriseArchitecture