Multihoming in a BGP EVPN VXLAN fabric is a redundancy feature that

• provides redundant connections between a host or Layer 2 switch and the EVPN VXLAN network

• connects hosts or Layer 2 switches to the EVPN VXLAN network through either single-homing or multihoming, and

• supports RFC 7432 and RFC 8365 for VXLAN encapsulation-based EVPN multihoming capabilities on Cisco Catalyst 9000 Series switches.

Single-homing is a network connectivity method that

• allows you to connect a host or Layer 2 switch to a single VTEP in the EVPN VXLAN network

• does not support redundancy in the connection between the host or access device and the VTEP, and

• results in connection loss when the active link breaks down, making single-homed topologies not always reliable and efficient.

Multihoming allows you to connect a host or Layer 2 switch to more than one VTEP in a EVPN VXLAN network. This connection provides redundancy and allows network optimization. Redundancy in connection with VTEPs ensures that there is no traffic disruption when a network failure happens. Multihomed topologies are more reliant, secure, and efficient than single-homed topologies.

Multihoming operates in single-active and all-active redundancy modes. In both modes, the connected host or access device connects to the VTEPs through a set of links that together represent an Ethernet segment, identified by a globally unique Ethernet segment ID.

This Ethernet segment ID must also be part of the configuration on the VTEP interface that connects the multihomed host or network device. All traffic forwarded between the VTEPs and the host or Layer 2 switch passes through this Ethernet segment.

ESI-MH in single-active redundancy mode is an EVPN configuration that

• allows two VTEPs to act as an ESI-MH pair with only one VTEP forwarding traffic for a particular Ethernet-segment

• results in multiple VLANs on the physical link with a single link active for a given VLAN, and

• enables fabric-enabled VLANs and traditional Layer 2 VLANs to co-exist on the Ethernet-segment enabled trunk-downstream access interface from the VTEPs.

Migration between single-homed and multihomed network topologies is a BGP EVPN VXLAN capability that

• allows transition from a single-homed topology to a multihomed topology

• enables removal of redundancy from a multihomed topology to move back to a single-homed topology, and

• requires corresponding changes to the Ethernet segment configuration to prevent traffic loops and traffic blackholing.