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VXLAN/EVPN Forwarding Characteristics

Chapter Description

In this chapter from Building Data Centers with VXLAN BGP EVPN: A Cisco NX-OS Perspective, the author team discuss two different options for handling BUM or multidestination traffic— leveraging multicast replication in the underlying network and using a multicast-less approach called ingress replication.


This chapter provides an in-depth discussion of the core forwarding capabilities of a VXLAN BGP EVPN fabric. For carrying broadcast, unknown unicast, and multicast (BUM) traffic, the chapter examines both multicast and ingress replication, coupled with the inclusive multicast Route type support with BGP EVPN. It also discusses enhanced forwarding features that allow for reducing ARP and unknown unicast traffic within the fabric. Perhaps the key benefit of a BGP EVPN fabric is the realization of a distributed anycast gateway at the ToR or leaf layer that allows for optimal forwarding of both Layer 2 and Layer 3 traffic within the fabric, using IRB semantics. Efficient handling of endpoint mobility with BGP EVPN is also described, as well as how to handle dual-attached endpoints with vPC-based deployments. Finally, the chapter concludes with a description of how DHCP relay functionality can be implemented in environments with distributed IP anycast gateway.

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