Connectivity Guide

The control plane functions include:
• Initiate BGP peering with all neighbor leaf nodes.
• Advertise BGP routes to all BGP peers.
• In the underlay network, initiate and maintain the routing adjacencies with all leaf and spine nodes.
The data plane functions include:
• Perform only the underlay route processing based on the outer header in VXLAN encapsulated packets.
• Does not perform VXLAN encapsulation or decapsulation.
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 be advertised to the peers. Tunnel endpoints are advertised as Type 3 EVPN routes. MAC/IP
addresses are advertised 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 needs
to be advertised using EVPN must be associated with an EVI. In OS10, you can congure EVIs in auto-EVI or manual conguration mode.
• Auto-EVI — After you congure a virtual network on a VTEP, auto-EVI mode automatically creates an EVPN instance. The route
distinguisher and route target values are automatically generated:
– The EVI ID is auto-generated with the same value as the virtual-network ID (VNID) congured on the VTEP and is associated with
the VXLAN network ID (VNI).
– A Route Distinguisher (RD) is auto-generated for each EVI ID. A Route Distinguisher maintains the uniqueness of an EVPN route
between dierent EVPN instances.
– A Route Target (RT) import and export value are auto-generated for each EVI ID. A Route Target determines how EVPN routes are
distributed among EVPN instances.
• Manual EVI conguration — If you need to specify the Route Distinguisher and Route Target values, manually congure EVPN
instances and associate each EVI with the overlay virtual network using the VXLAN VNI. The EVI is activated only when the virtual
network, Router Distinguisher, and Route Target values are congured.
In manual EVI conguration, you can either manually congure the RD and RT or have them auto-congured.
Route distinguisher
The Route Distinguisher is an 8-byte identier, which uniquely identies an EVPN instance (EVI). Each EVPN route is prexed with a unique
RD and exchanged between BGP peers, making the tenant's route unique across the network. In this way, overlapping address spaces
among tenants are supported.
A Route Distinguisher for each EVI can be auto-generated or manually congured. In auto-EVI mode, the RD is auto-generated. In manual
EVI conguration mode, the RD can be auto-generated or manually congured.
As specied in RFC 7432, a manually congured RD are encoded in the format: 4-octet-ipv4-address:2-octet-number. An
auto-generated RD has the format:
vtep-ip-address:evi.
Route target
While a Route Distinguisher maintains the uniqueness of an EVPN route among dierent EVIs, a Route Target controls the way in which
EVPN routes are distributed among EVIs. Each EVI is congured with an import and export Route Target value. BGP EVPN routes
advertised for an EVI carry the export Route Target associated with the EVI. A receiving VTEP downloads information in the BGP EVPN
route to EVIs that have a matching import Route Target value.
The Route Target import and export for each EVI can be auto-generated or manually congured. In auto-EVI mode, the RT is auto-
generated. In manual EVI conguration mode, the RT can be auto-generated or manually congured.
The Route Target consists of a 2-octet type and a 6-octet value. If a Route Target is auto-congured, the encoding format is dierent for a
2-byte and 4-byte AS number (ASN):
552
VXLAN