SD‑GEEKSDesign Learning SeriesFREE DESIGN LAB · 01TRANSPORT TECHNOLOGIES / DMVPN
One design decision. Ten matrix rows. Reconcile the requirements, choose the right mechanisms, and prove your design.
EXHIBIT A
Northstar Logistics needs a warm backup and encrypted direct branch traffic.
Open full-size topology ↗
One Phase 3 cloud: 10.255.0.0/24. Both hubs share a DC. Lines show logical overlay connectivity; direct spoke shortcuts form on demand.
EXHIBIT B
I suggest keeping H2 shut until we need it and disabling hub next-hop-self for direct branch traffic. Please review those assumptions against the required failure behavior.
Keep both routing adjacencies up. During healthy operation only H1 should carry spoke-to-DC traffic; use H2 after H1 fails and return to H1 when it recovers. H2 must already be a feasible successor at every spoke. Preserve branch metrics and the core return policy. The earlier shutdown proposal does not meet this requirement.
Limit the change to a DC-only outbound offset on one hub Tunnel0. Choose one of the tested values: 12,800, 51,200 or 6,400. This exercise protects a hub failure; both hubs share the DC, and full DC disaster recovery is outside this change.
mGRE/IPsec; dual NHS registration and unicast/multicast maps; hub dynamic multicast mapping; connected-only stub spokes; active T0 and hub-core interfaces; passive branch LANs.
Classic EIGRP 100, default K values, variance 1. Exact branch prefixes; no overlay summary or default. Hub split horizon and next-hop-self start ON. Core return routing already prefers H1 and fails over to H2.
EXHIBIT C
| Spoke | H1 total = FD | H2 RD | H2 total |
|---|---|---|---|
| S1 | 307,200 | 281,600 | 307,200 |
| S2 | 332,800 | 281,600 | 332,800 |
| S3 | 294,400 | 281,600 | 294,400 |
Measured rule: an H2 outbound DC offset d adds exactly d to both H2 RD and each spoke’s total via H2. H1 is unchanged. No lower historical FD exists.
Synthetic instructional measurements. Judge every spoke, not just S1.
Read the operating state named in each row before selecting. Healthy operation, a single failure, and a restored path are different cases; the selections must satisfy the supplied requirements for that case.
Use the final stakeholder requirements and the per-spoke metric exhibit to approve the dual-hub EIGRP design. Decide the healthy and failure forwarding behaviour, the permitted metric change and its feasibility implications for all three spokes.
How to answer: Complete all ten rows with one selection per row. Each row is a separate design decision; read its explanatory prompt before choosing. For slash-separated options, read the operating states from left to right in the order defined by that row. Correct rows earn independent partial credit.
Select one cell in each row. Each correct row earns 10 points; partial credit is awarded across the matrix.