August 2025

DHCP in Cisco ACI

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The Dynamic Host Configuration Protocol (DHCP) automates IP address assignment through a four-step dialogue known as DORA: Discover, Offer, Request, and Acknowledge. This process ensures that clients can join a network without manual IP configuration.

Because DHCP discovery messages are broadcasts, they cannot cross Layer 3 boundaries. A DHCP relay policy may be used when the DHCP client and server are in different subnets. ACI’s built-in DHCP relay function solves this by intercepting the broadcast and forwarding it as a unicast packet to a configured DHCP server.

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EPG vs. ESG

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The evolution of Cisco ACI’s security model from EPGs to ESGs represents a significant maturation of the platform. While EPGs were instrumental in ACI’s original design, their tightly coupled nature presented challenges in large-scale and complex environments. The ESG model directly addresses these limitations by providing a more flexible, scalable, and operationally efficient approach to security.

The ESG’s ability to decouple security policy from forwarding, expand its scope to the VRF level, and leverage dynamic endpoint selectors allows network professionals to align their security posture with business logic in a way that was not previously possible. This shift not only simplifies complex tasks like route leaking and brownfield migrations but also conserves valuable hardware resources.

The decision of whether to primarily utilize EPGs or ESGs hinges on your specific application requirements and design philosophy.

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ACI EPG vs. ESG – Quiz

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Hey there, ACI enthusiasts! Ready to put your knowledge to the test? – Cisco ACI: EPG vs. ESG Quiz! Test your knowledge on the differences between EPGs and ESGs in Cisco ACI.

In the world of Cisco Application Centric Infrastructure (ACI), understanding the subtle but critical differences between network constructs is key to building a robust and secure fabric. While you might be very familiar with Endpoint Groups (EPGs) and their role in defining both forwarding and security policy, ACI 5.0 introduced a new player to the game: Endpoint Security Groups (ESGs).

Are you ready to see if you can tell the difference? Let’s dive in and find out if you’re an EPG expert or an ESG master!

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