Sep 18, 2020

How to Solve EVPN Implementation Challenges

Current data center trends indicate that the future holds both more and larger data centers.  Data centers don’t exist in isolation, as they proliferate in number and size it is crucial that applications can leverage compute and storage that is geographically diverse. Applications, storage, and servers have to be reliably connected, making data center interconnectivity a topic of choice in a web-scale, cloud-based world where access to data is key.  And yet, applications continue to be deployed that thrive on assuming they have local L2 adjacency. In data centers, networks depend on flood-and-learn techniques for data-plane learning. When a frame needs to be sent to an unknown destination, the sender needs to know the destination MAC address and sends a broadcast query for the destination MAC address. Every node in the L2 network receives the request and only the device with the proper MAC address will respond to the sender while others ignore the message. When the sender receives the reply, the sender’s MAC address is added to the ARP cache. Eventually, the cache will expire and the data plane learning will repeat. There are many inefficiencies if broadcast, unknown unicast, and multicast (BUM) traffic is handled poorly.

So, the modern network has become a story about distributed network nodes that need to integrate seamlessly and EVPN-VxLAN is a technology that helps a network engineer deal with the scale and proliferation of L2 broadcast domains. 

Let’s look at the EVPN control plane first. 

What is EVPN?

EVPN builds on the operational experience and uses the BGP control plane to exchange L2 and L3 reachability information. It introduces a new model for ethernet services but works in the same way as a routing protocol by leveraging  MP-BGP (Multiprotocol-BGP) to distribute MAC and IP information optimizing the flood-and-learn challenges of traditional bridging. The MAC advertisement function is moved from the data plane to the control plan, making MAC learning very efficient. EVPN can support different encapsulation technologies in a data plane that can be varied based on application scenarios. In practice, EVPN with VxLAN or MPLS are the most popular choices.

EVPN technology is standardized in RFC7432, so there is no need to lock into a particular vendor’s proprietary features. It leverages the well-known efficiencies of BGP and has IPv6 support fully integrated. It helps to integrate L2/L3 services, enables workload mobility across data centers, and allows for multi-tenancy. EVPN instantly simplifies DCI with scalable and efficient technology. 

In short, it makes L2 applications work properly across data centers and other L3 interconnects. 

Benefits of an EVPN implementation include: 

  • Less unicast and ARP flooding because of MAC learning within the control plane 
  • Elegant and efficient handling of broadcast, unicast and multicast (BUM) traffic 
  • Distributed L3 gateways that optimize virtual machine traffic 
  • Enables active-active, dual-homed server connections 
  • Enables quick convergence and failure when moving Virtual Machines 
  • Leverages the known scalability of BGP control 
  • Enables Virtual Networks (VNs) spanning racks with efficient cross-VNs traffic routing 
  • Extends L2/L3 connectivity between data centers and from the data center to end-users

Why is EVPN challenging? 

Despite these impressive benefits, EVPN technology has been slow to mature. Different vendors have implemented varying interpretations of the standard, causing incompatibilities in multi-vendor environments, sometimes necessitating a wholesale overhaul of the equipment in your network. EVPN technology is intrinsically scalable in operation, but configuring it at scale can be complex, causing configuration errors that lead to network instability. 

The current state of EVPN can be summarized as standards-based, providing numerous benefits, but still presenting some deployment and implementation challenges

Apstra Solves EVPN Implementation Challenges

With multi-tenant support via VRFs and enhanced inter-rack L2 connectivity, EVPN provides a scalable solution allowing for the isolation of different virtual networks while still enabling routing and switching between them where necessary. EVPN efficiently accommodates north-south and east-west traffic flows. 

The many operational benefits of EVPN technology can be achieved if the complexity of the configuration, internetworking and operational telemetry is abstracted and automated from a logical orchestration system that delivers and ensures reliability and stability in the network. 

Apstra’s Intent-Based Networking solution empowers your organization to automate all aspects of the network design, build, deploy, and operate phases. Apstra leverages advanced Intent-Based Analytics to continually validate the network, thereby eliminating complexity, vulnerabilities, and outages resulting in a secure and resilient network. Automation of the complex configuration tasks allows you to continue to address your existing application connectivity requirements while transitioning to a modern L3 leaf-spine data center architecture for better agility and scale.

Learn more about Apstra

Apstra puts Easy in EVPN: Video

Networking Field Day: Apstra Multi-Vendor EVPN Demonstration