VXLAN Part XV: Analysis of the BGP EVPN Control Plane Operation

Document Status: Unfinished
Edited: Monday, 7 January 2019

This chapter covers the following topics:

MAC address learning process (Intra-VNI switching): This section describes how the local VTEP switch learns the MAC addresses of its’ directly connected hosts from the ingress frame and installs the information into the MAC VRF in Layer 2 Routing Information Base (L2RIB) by the L2 forwarding component (L2FWDER). This section also shows how the local VTEP switch advertises the MAC address information to the remote VTEP switch by using BGP EVPN Route Type 2 advertisement (MAC Advertisement Route) and how the Remote VTEP switch installs information into MAC VRF in L2RIB and from there into MAC address table. Intra-L2VNI (Switching) Data Plane operation is explained at the end of the section with various frame capture examples. The white “MAC line” represents these processes in figure 7-1.

MAC-IP address learning process (ARP for Intra-VNI switching and ): This section gives a detailed description how the local VTEP switch learns the IP addresses of its’ locally connected hosts from ARP messages generated by the host and how the Host Mobility Manager component (HMM) installs the information into the IP VRF. This section also shows how the local VTEP switch advertises the IP address information to the remote VTEP switch by using BGP EVPN Route Type 2 (MAC Advertisement Route) advertisement and how the remote VTEP switch installs this information into IP VRF in L2RIB as well as into L3RIB of VRF TENANT77. In addition, this section explains how the ARP Suppression mechanism use MAC-IP binding information to reduce BUM (Broadcast, Unknown Unicast, and Multicast) traffic in VXLAN Fabric. The grey “IP line” represents these processes in figure 7-1.

Prefix advertisement: This section covers how the local VTEP switch redistributes its Anycast Gateway (AGW) subnets into BGP and advertises this information to the remote VTEP switch by using BGP EVPN Route Type 5 (IP Prefix Route) advertisement. This section also explains how the information is used to discover silent hosts. This section also describes how the remote VTEP installs the route from the BGP into local L3RIB. The black “Prefix line” represents these processes in figure 7-1.

Figure 1-1: BGP EVPN Control Plane Operational Overview.