NX-OS Forwarding Constructs For VXLAN/EVPN
In this post we will look at the forwarding constructs in NX-OS in the context of VXLAN and EVPN. Having knowledge of the forwarding constructs helps both with understanding of the protocols, but also to assist in troubleshooting. BRKDCN-3040 from Cisco Live has a nice overview of the components involved:

There are components that are platform independent (PI) and platform dependent (PD). Below I’ll explain what each component does:
- ARP – Information from ARP requests/responses is needed to build adjacencies. The information learned from ARP is used to populate IP address field in RT2 and hence also to populate the ARP suppression cache.
- IPv6 ND – ND fills the role of ARP, but for IPv6.
- Adjacency Manager – Resolves directly attached hosts MAC addresses.
- Host Mobility Manager – Tracks the endpoints and their movements.
- L2FM – The Layer2 Forwarding Manager. A platform dependent component that programs ASICs for L2 forwarding. Keeps track of MAC addresses, their placement and moves, and synchronizes this information across ASICS, line cards, and vPC peers when vPC is in use.
- MFDM – Multicast Forwarding Database Manager. A platform dependent component that programs ASICs with information to perform multicast forwarding.
- L2RIB – The component that handles Continue reading