Refer to the exhibit. Which routing solution is the most scalable to connect the branches to the HQ and to connect the branches together over the internet using DMVPN?

Question

Options

• AEIGRP
• BEIGRP with the branch routers setup as stubs
• COSPF with each branch router as an ABR
• DIS-IS L2 in all locations
• EOSPF Area 0 in all locations

• A
  12% (5)
• B
  77% (33)
• C
  7% (3)
• D
  2% (1)
• E
  2% (1)

Explanation

EIGRP stub is the correct answer because in a DMVPN hub-and-spoke topology, branch (spoke) routers configured as stubs tell the HQ hub not to send EIGRP queries their way when a route goes down. This eliminates the query propagation problem - the primary EIGRP scalability killer - preventing SIA (Stuck-In-Active) conditions that plague large deployments. Stub spokes advertise only their connected/summary routes to the hub, keeping the design simple and lightweight as branch count grows.

Why the distractors fail:

• A (EIGRP without stub): Works but doesn't scale - unconstrained query flooding across hundreds of branches causes SIA timeouts and convergence problems.
• C (OSPF with branch routers as ABRs): ABRs must maintain multiple LSDB copies and manage inter-area routing - complex and resource-heavy for simple branch routers; also incorrect design for this topology.
• D (IS-IS L2 everywhere): IS-IS L2 is an ISP/carrier protocol for large backbone networks, not suited for enterprise DMVPN branch deployments.
• E (OSPF Area 0 everywhere): All branches in a single area means every router floods and stores the full topology database - this gets exponentially worse as branches are added, the opposite of scalable.

Memory tip: Think "Stub = Stop Unnecessary Broadcasts" - stubs block queries from propagating through spokes, and in DMVPN, queries are the enemy of scale.

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