Modern enterprise campuses require a secure fabric networking solution that seamlessly supports large-scale virtual and logical networks over a robust physical network infrastructure. EVPN multihoming-based networks offer a simplified and resilient architecture evolving from legacy STP protocol-based enterprise campus networks to a non-blocking Layer 2 fabric.

The EVPN VXLAN-enabled fabric core networks introduce new possibilities for EVPN multihomed Layer 2 networks by enabling secured wired and wireless segmented and extended networks that address critical technical and business requirements.

The following illustration displays EVPN multihoming in fabric networks

Enterprise campuses can be designed and deployed using a single unified BGP control plane that addresses the traditional Layer 2 and Layer 3 networking requirements at the access layer while supporting a modern fabric network at the core. The unified BGP control plane simplifies network operations by distinctly managing multi-domain routing and bridging functions, enabling seamless integration of the access and core networks.

BGP EVPN multihoming-based networks represents a shift from the traditional flood-based networks to control-plane driven architecture that supports non-blocking and resilient enterprise campus networks. Host addresses—including the MAC, IPv4 or IPv6, multicast—are statefully discovered and synchronized across peer systems, enabling all-active data forwarding in BGP EVPN multihoming networks.

As the BGP control plane role expands into traditional networks, processing demands may increase due to additional BGP prefix tables supporting EVPN multihoming auto-generated prefixes.

Cisco Catalyst 9000 series switches support both standard non-hierarchical and hierarchical BGP peering mode between leaf and spine devices, facilitating the exchange of fabric and EVPN multihoming network prefixes.

To address scalability and performance requirements, Catalyst 9000 series switches can implement a two-tier hierarchical control-plane network in large deployments.

The general non-hierarchical BGP EVPN VXLAN network implementation follows a standard single tier BGP peering model where all fabric devices peer directly with each other to dynamically exchange routes and build the VXLAN forwarding tunnels.

The EVPN multihoming-enabled non-hierarchical fabric network implementation follows a standard iBGP or eBGP peering model between the spine and EVPN multihoming-enabled leaf or border system.

In large scale enterprise campus network environments, spine layer devices require additional resources such as processing power and memory to handle standard fabric host information, such as MAC addresses, MAC/IP bindings and network prefixes (IPv4/IPv6) along with EVPN multihoming auto-generated routes received from each leaf or border system.

Hierarchical and structured networking is fundamental to supporting scalable and resilient campus networks, and EVPN multihoming-based fabric networks follow hierarchical BGP routing design principles for better scalable networking solutions.

The two-tier BGP peering in EVPN multihoming networks assists in subdividing route management between peers by separating Layer 2 networking from scalable network connectivity towards the spine layer.

The iBGP peering between a pair of Cisco Catalyst 9000 series switches exchanges all auto-generated EVPN multihoming network prefixes to build reliable and scalable traditional Layer 2 networks.

Cisco Catalyst 9000 series switches in EVPN multihoming leaf role follow standard parallel iBGP or eBGP peering with a pair of spine switches advertising network prefixes based on EVPN fabric overlay network types. The conditional network prefix announcement to spine switches enables enhanced flexibility, scale, performance, and resiliency across the network.

BGP EVPN VXLAN provides a flexible, virtual networking solution that addresses key networking use cases by combining a wide range of overlay architectures.

Such business-driven network architectures enable multidimensional benefits for scalable and secure segmented overlay networks in EVPN multihoming networks. Network administrators can build overlay networks with a “route first” mindset that can conditionally extend IP or VLAN networks between targeted Ethernet segment network devices to meet application requirements.

The following figure illustrates three overlay network types in EVPN multihoming networks.

Enterprise campuses require flexible networking solutions that support both modern secure fabric networks and backward-compatible traditional Layer 2 or Layer 3 networks. Cisco Catalyst 9000 series switches with EVPN multihoming-enabled EtherChannel trunk interfaces provide this flexibility by bundling multiple VLANs, each delivering distinct networking services.

Network administrators can program some VLANs to operate traditional IP-based networks in the underlay, while mapping other VLANs to IP VRFs or MAC VRFs to route and bridge over the VXLAN fabric.