Users Guide

Leaf nodes are typically top-of-rack (ToR) switches in a data center network. They act as the VXLAN tunnel endpoints and
perform VXLAN encapsulation and decapsulation. Leaf nodes also participate in the MP-BGP EVPN to support control plane and
data plane functions.
Control plane functions include:
● Initiate and maintain route adjacencies using any routing protocol in the underlay network.
● Advertise locally learned routes to all MP-BGP EVPN peers.
● Process the routes that are received from remote MP-BGP EVPN peers and install them in the local forwarding plane.
Data plane functions include:
● Encapsulate server traffic with VXLAN headers and forward the packets in the underlay network.
● Decapsulate VXLAN packets received from remote VTEPs and forward the native packets to downstream hosts.
● Perform underlay route processing, including routing based on the outer IP address.
Spine nodes
The role of a spine node changes based on its control plane and data plane functions. Spine nodes participate in underlay route
processing to forward packets and in the overlay network to advertise EVPN routes to all MP-BGP peers.
Control plane functions include:
● Initiate BGP peering with all neighbor leaf nodes.
● Advertise BGP routes to all BGP peers.
● Initiate and maintain routing adjacencies with all leaf and spine nodes in the underlay network.
Data plane functions include:
● Perform only underlay route processing based on the outer header in VXLAN encapsulated packets.
● Does not perform VXLAN encapsulation or decapsulation.
The BGP EVPN running on each VTEP listens to the exchange of route information in the local overlay, encodes the learned
routes as BGP EVPN routes, and injects them into BGP to advertise to the peers. Tunnel endpoints advertise as Type 3 EVPN
routes. MAC/IP addresses advertise as Type 2 EVPN routes.
EVPN instance
An EVPN instance (EVI) spans across the VTEPs that participate in an Ethernet VPN. Each virtual-network tenant segment,
that is advertised using EVPN, must associate with an EVI. In OS10, configure EVIs in auto-EVI or manual configuration mode.
● Auto-EVI — After you configure a virtual network on a VTEP, auto-EVI mode automatically creates an EVPN instance. The
route distinguisher (RD) and route target (RT) values automatically generate:
○ The EVI ID autogenerates with the same value as the virtual-network ID (VNID) configured on the VTEP and associates
with the VXLAN network ID (VNI).
○ A Route Distinguisher autogenerates for each EVI ID. A Route Distinguisher maintains the uniqueness of an EVPN route
between different EVPN instances.
○ A Route Target import and export value autogenerates for each EVI ID. A Route Target determines how EVPN routes
distribute among EVPN instances.
● Manual EVI configuration — To specify the RD and RT values, manually configure EVPN instances and associate each EVI
with the overlay virtual network using the VXLAN VNI. The EVI activates only when you configure the virtual network, RD,
and RT values.
In manual EVI configuration, you can either manually configure the RD and RT or have them autoconfigured.
NOTE: Dell Technologies recommends using manual EVI for interoperability with network equipment vendors.
Route distinguisher
The RD is an 8-byte identifier that uniquely identifies an EVI. Each EVPN route is prefixed with a unique RD and exchanged
between BGP peers, making the tenant route unique across the network. In this way, overlapping address spaces among
tenants are supported.
You can autogenerate or manually configure a RD for each EVI. In auto-EVI mode, the RD is autogenerated. In manual EVI
configuration mode, you can autogenerate or manually configure the RD.
As specified in RFC 7432, a manually configured RD is encoded in the format: 4-octet-ipv4-address:2-octet-number.
An autogenerated RD has the format: vtep-ip-address:evi.
Route target
While a RD maintains the uniqueness of an EVPN route among different EVIs, a RT controls the way the EVPN routes are
distributed among EVIs. Each EVI is configured with an import and export RT value. BGP EVPN routes advertise for an EVI carry
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