SD-Access Brownfield Deployment: Manual Underlay Requirement
Short answer
D In a brownfield SD-Access deployment, the existing underlay must be handled via Manual Underlay configuration to preserve current routing and avoid disruption, as automated tools like LAN Automation are intended for greenfield builds.
Question
Key Takeaways
The question tests the distinction between greenfield (automated/LAN Automation) and brownfield (manual/existing) underlay strategies in SD-Access.
For Cisco SD-Access brownfield deployments, Manual Underlay is the required configuration approach to integrate existing infrastructure without disrupting active services.
Common mistake: Candidates often choose LAN Automation because it is a key DNA Center feature, but it only works on unconfigured greenfield devices, not live brownfield networks.
Expert Analysis
Brownfield Context vs. Tooling Capability
In a Cisco SD-Access brownfield deployment, the existing network infrastructure (Layer 2/3 underlay) is already operational and configured with production routing protocols (e.g., OSPF, EIGRP). The defining constraint of this scenario is that the underlay cannot be rebuilt or wiped. LAN Automation is a feature designed specifically for greenfield deployments where switches are unconfigured and ready to be discovered and built out from scratch using IS-IS. Attempting to use LAN Automation on a live brownfield network would disrupt existing services by reconfiguring interfaces and wiping routing tables.
Manual Underlay as the Necessity
Because the underlay exists, the engineer must perform a Manual Underlay configuration. This involves importing the existing topology into Cisco DNA Center and manually mapping it to the fabric nodes. While DNA Center facilitates the overlay (VXLAN, policies, segmentation) and can automate aspects of the migration, the underlying IP routing and switching logic must be preserved and acknowledged via manual configuration steps within the tool's context. Automated underlay options assume a clean slate, which contradicts the brownfield definition.
Trap Analysis
The primary trap is selecting LAN Automation (Option B) because it is a popular DNA Center feature. However, as noted in community discussions, LAN Automation is incompatible with active production networks. Another distractor is Subnet Stretching (Option A), which is a specific technique for migrating VLANs during the overlay build, not the fundamental underlay configuration method. The phrase "must be taken with Cisco DNA Center" refers to the workflow execution; while manual underlay sounds CLI-centric, in the SDA brownfield migration workflow, the underlay validation and import process is managed through the DNA Center interface, distinguishing it from pure greenfield automation.
Operational Consequence
Choosing LAN Automation in a brownfield scenario leads to network outage due to unexpected interface resets and routing protocol flaps. Choosing Manual Underlay ensures service continuity while allowing the overlay to be built atop the stable existing infrastructure.
Official Reference
This link opens the official vendor documentation in a new tab.
Exam Strategy
When encountering 'brownfield' keywords in SD-Access questions, immediately eliminate any option suggesting 'automation' of the physical or Layer 3 underlay (like LAN Automation or Automated Underlay). Focus on solutions that preserve existing state, such as Manual Underlay or Subnet Stretching for specific VLAN migrations. Always verify if the option disrupts live traffic.
Frequently Asked Questions
Can LAN Automation be used in brownfield SD-Access?
What does Manual Underlay involve in DNA Center?
Community Votes
57% of anonymous learners picked answer B. Votes are pick records left by other test-takers — they are not the verified answer.
Discussion 11 contributions
Compiled from public community threads and reader submissions, lightly edited for clarity. Handles and vote tallies are shown as recorded, and comments reflect the views of individual contributors.
From public community threads 11
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XalaGyan 👍 11In a brownfield deployment scenario, the deployment of the underlay network must be taken with manual configuration. The other configurations, such as subnet stretching, LAN automation, and automated underlay, can be done with the help of Cisco DNA Center.
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zzmejce 👍 7 Answered DCisco LAN automation workflow helps enterprise IT administrators prepare, plan, and automate greenfield networks. In the question, it is a brownfield deployment scenario and manual underlay is more appropriate.
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Reinier_veen 👍 3provided answer is correct. https://www.cisco.com/c/en/us/td/docs/cloud-systems-management/network-automation-and-management/dna-center/tech_notes/b_dnac_sda_lan_automation_deployment.html
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Nickplayany 👍 3 Answered DIsn´t it D here?!
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CKL_SG 👍 2 Answered BB - LAN Automation in Cisco DNA Center for configuration of Underlay in SDA LAN Automation for deployment—The configuration of the underlay can be orchestrated by using LAN Automation services in Cisco DNA Center. The LAN Automation feature is an alternative to manual underlay deployments for new networks and uses an IS-IS routed access design. Although there are many alternative routing protocols, the IS-IS routing protocol offers operational advantages such as neighbor establishment without IP protocol dependencies, peering capability using loopback addresses, and agnostic treatment of IPv4, IPv6, and non-IP traffic. Manual underlays are also supported and allow variations from the automated underlay deployment (for example, a different IGP could be chosen), though the underlay design principles still apply.
Show 6 more comments
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G_Singh12 👍 1 Answered DFor brownfield deployments, Deal with an existing, running production network where Layer 3 core/distribution routing, VLAN structures, and physical connections are already built and active. Since LAN Automation would wipe and reconfigure those active links, a Manual Underlay approach must be taken. The network engineer discovers or imports the existing underlay topology into Cisco DNA Center without altering its underlying operational state. LAN Automation is used in case of Greenfield deployments.
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Ernie71 👍 1It should be B- LAN automation. The question is regarding the action to take using DNA Center, and LAN automation is one of those actions (in addition to subnet stretching, and automated underlay). If the question was "which configuration deployment must be taken with deployment of the underlay network", then the answer would be D- Manual Underlay. As such the correct answer is B.
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dougj 👍 1 Answered BAnswer is B. In a brownfield scenario Catalyst centre automates the configuration of both the underlay (e.g., routing protocols like IS-IS) and the overlay (e.g., VXLAN) of the SD-Access fabric. This removes the need for manual, command-line configuration on each switch, which is a key benefit for a brownfield migration
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guerreroa25 👍 1 Answered BB it.s correct, coz, n a brownfield deployment scenario, the underlay network already exists and must be manually configured. Cisco DNA Center can assist with the configuration of the overlay network, including policies and virtual networks.
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Seb82 👍 1 Answered BI was absolutely sure it's D, but then I re-read the question and realized this "must be taken WITH Cisco DNA center". Manual underlay is not done "with" Cisco DNA center, so the only logic answer can be LAN automation
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Seb82 👍 1I just reconsidered this few days later. While the question asks for one answer only, the correct one can only be Manual underlay (configuration). The other 3 are done together.
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