Most networks break not because of traffic load, but because one device or one path becomes a silent single point of failure. Even well-funded teams rely on a single routing plane, a single control processor, or single uplink bundles and outages happen the moment something in that chain disappears.
Downtime usually comes from
- Missing redundancy
- Tightly coupled hardware
- Poor separation between forwarding and control functions
- Inconsistent topology design across sites
What Most Teams Do Today?
Many architectures still follow a “scaled-up box” mindset: one big chassis, one plane, one control engine. When scale increases, they add more powerful boxes instead of distributing load.
Teams often assume redundancy exists because the hardware supports it, but logical redundancy is missing, everything still depends on a single plane or domain.
Why This Fails?
- A single hardware failure cascades across the network
- Both traffic and control traffic pass through the same risk zones
- Unbalanced designs create unpredictable blast radius when something breaks
- Multiple planes exist physically, but routing behavior treats them as one
Framework / Approach
Step 1: Define
Identify all areas where one element can take down traffic. This includes routers, route reflectors, fabric modules, or optical paths.
Step 2: Diagnose
Map how traffic would behave if any one plane, bundle, or route reflector disappears. Many teams discover both planes are technically separate but still bound to a single IGP instance.
Step 3: Decide
Choose the right architecture:
- Fixed vs modular
- Single-plane vs multi-plane
- Full vs partial hardware redundancy
- Centralized vs distributed designs
Aim for a structure where the blast radius remains small, no matter where the failure occurs.
Step 4: Deliver
Implement a resilient layout using
- Dual physical planes
- Dual logical planes
- Separated IGP domains when appropriate
- Traffic-steering policies based on service needs
Case Study / Example
A regional provider had two data centers with identical hardware but treated both as one giant cluster.
Actions Taken
- Split the network into two logical planes
- Distributed routing roles (RR, PE functions) across both planes
- Moved traffic classes (internet, mobility, critical video) to separate steering policies
- Added diversity in optical paths by isolating conduits
- Introduced route filtering to stop accidental cross-plane leaks
Results
- 40 percent fewer customer-impacting incidents
- Failures isolated to half of the network instead of full collapse
- Full switchover kept services live during maintenance
- All improvements implemented within a two-month window
What Didn’t Work
Running both planes under a single IGP initially created unnecessary churn, forcing the team to separate domains later.
Playbook / Checklist
- Map physical redundancy and compare it with logical routing behavior
- Segment routing planes instead of relying on a single-domain backbone
- Place RRs, PEs, and core routers in balanced roles across planes
Conclusion & Next Step
High availability is not about buying bigger boxes — it’s about isolating failure impact.
A simple redesign of planes, routing domains, and redundancy paths can reduce outages dramatically.
In Part 2, we shift to fast failure detection and the mechanisms that actually sense failure before loss becomes visible
At TelenceSolutions
We continue to help professionals build scalable, intelligent networks through real-world, hands-on learning — from OSPF and IS-IS fundamentals to BGP, SD-WAN, and AI-driven automation.