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Migrate a Traditional Enterprise Network to a Juniper Campus Fabric

date_range 19-Mar-25

This document details a strategy that can be used to migrate a traditional enterprise network-based architecture to a Juniper Campus Fabric EVPN-VXLAN architecture.

Juniper’s campus fabric leverages EVPN VXLAN as the underlying technology for small, mid, and large enterprise deployments. You can build and manage campus fabric by using Mist’s Wired Assurance Cloud-ready framework. For additional information on Juniper’s Campus Fabric, see Juniper Mist Wired Assurance datasheet.

Video 1: Three Step Campus Fabric
Show Transcript

This migration strategy focuses on an enterprise network consisting of the traditional 3-stage architecture of access, distribution, and core. In this example, core provides layer 3 connectivity to all users, printers, access points (APs), and so on. And the core layer interconnects with dual WAN routers using standards based OSPF or BGP technologies.

Figure 1: Traditional Enterprise Network Traditional Enterprise Network

At a high-level, migration from a traditional enterprise network to a Juniper campus fabric architecture involves the following steps:

  1. Build a campus fabric architecture in parallel to the existing enterprise network.
  2. Interconnect the campus fabric to the existing network using a services block.
  3. Migrate VLANs one by one to the campus fabric.
  4. Migrate the critical infrastructure such as DHCP server and RADIUS to the services block.
  5. Migrate WAN router(s) to the services block.
  6. Decommission the existing enterprise network once all the connectivity is verified.

Build Campus Fabric in Parallel to the Existing Network

As the first step, build a campus fabric by using Mist’s Wired Assurance framework. This step allows you to deploy an operational campus fabric in parallel to the existing network. In this example, we choose the campus fabric IP Clos architecture because the customer has a micro-segmentation strategy deployed at the access layer. The customer has chosen the following Juniper equipment to be deployed within the Campus Fabric IP Clos architecture:

  • QFX5120 switches (core layer)
  • QFX5120 switches (distribution layer)
  • EX4100 and EX4400 switches in Virtual Chassis mode (access layer)
  • QFX5120 switches (services block)

See also: Configure Campus Fabric IP Clos.

Figure 2: Co-existence of Campus Fabric with Enterprise Network Co-existence of Campus Fabric with Enterprise Network

Interconnect the Campus Fabric to the Existing Network

You can use the services block to interconnect the campus fabric with the enterprise network. You can do this by using ESI-LAG technologies at layer 2, or the standard routing protocols such as BGP or OSPF if layer 3 connectivity is required. In this case, we interconnect the services block to the core enterprise using OSPF.

Figure 3: Services Block Interconnects with the Core Using OSPF Services Block Interconnects with the Core Using OSPF

The loopback reachability between the two networks should be established through the services block. For example, the campus fabric build assigns loopback addresses to each device. By default, these addresses are part of the same subnet. OSPF should exchange these addresses with routable prefixes sent by the core layer through the services block. The end-user should verify reachability between these prefixes before moving to the next step.

Migrate VLANs to the Campus Fabric

This process requires you to remove each VLAN and associated layer 3 interface from the enterprise network. You need to migrate all devices within the VLAN to the campus fabric and then have the end-user verify full connectivity from the devices on the migrated VLAN to the applications and devices on the enterprise network. The following summarizes this step:

  • Migrate VLANs to campus fabric by disabling or removing the layer 3 subnet from the current network.
  • Users and devices migrate to the access layer of the campus fabric.
  • Layer 3 interconnect provides reachability on a VLAN-by-VLAN basis.
  • Users and devices must validate all application reachability before moving to the next VLAN.
Figure 4: All VLANs and Access Devices Migrated to the Campus Fabric All VLANs and Access Devices Migrated to the Campus Fabric

Migrate the Critical Infrastructure to the Services Block

Juniper recommends dual homing of each critical infrastructure service (such as DHCP server and RADIUS) to the services block. You can do this by using ESI-LAG technologies at layer 2, or the standard routing protocols such as BGP or OSPF if layer 3 connectivity is required. Accessibility of critical infrastructure services within the campus fabric and from the enterprise network should be verified before moving to the next step.

Figure 5: Critical Infrastructure Migration to the Services Block Critical Infrastructure Migration to the Services Block

Migrate WAN Router(s) to the Services Block

Mist lets you connect WAN router(s) to the services block using BGP or OSFP. After WAN routers are connected to the service block, verify the accessibility of WAN services to and from the campus fabric before moving to the next step.

Figure 6: WAN Routers Migration to the Services Block WAN Routers Migration to the Services Block

Decommission the Existing Enterprise Network

We recommend that you keep the enterprise network up and operational for at least one week after all services and applications are reachable without issue to and from the campus fabric. After that, decommission the existing enterprise network.

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