Connectivity Guide

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, 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 (RD) and route target (RT) values automatically generate:
– The EVI ID auto-generates with the same value as the virtual-network ID (VNID) congured on the VTEP and associates with the
VXLAN network ID (VNI).
– A Route Distinguisher auto-generates for each EVI ID. A Route Distinguisher maintains the uniqueness of an EVPN route between
dierent EVPN instances.
– A Route Target import and export value auto-generates for each EVI ID. A Route Target determines how EVPN routes distribute
among EVPN instances.
• Manual EVI conguration — To specify the RD and RT values, manually congure EVPN instances and associate each EVI with the
overlay virtual network using the VXLAN VNI. The EVI activates only when you congure the virtual network, RD, and RT values.
In manual EVI conguration, you can either manually congure the RD and RT or have them auto-congured.
Route distinguisher
The RD is an 8-byte identier that uniquely identies an EVI. Each EVPN route is prexed 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 auto-generate or manually congure a RD for each EVI. In auto-EVI mode, the RD is auto-generated. In manual EVI conguration
mode, you can auto-generate or manually congure the RD.
As specied in RFC 7432, a manually congured RD is 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 RD maintains the uniqueness of an EVPN route among dierent EVIs, a RT controls the way the EVPN routes are distributed
among EVIs. Each EVI is congured with an import and export RT value. BGP EVPN routes advertise for an EVI carry the export RT
associated with the EVI. A receiving VTEP downloads information in the BGP EVPN route to EVIs that have a matching import RT value.
You can auto-generate or manually congure the RT import and export for each EVI. In auto-EVI mode, RT auto-generates. In manual EVI
conguration mode, you can auto-generate or manually congure the RT.
The RT consists of a 2-octet type and a 6-octet value. If you auto-congure a RT, the encoding format is dierent for a 2-byte and 4-byte
AS number (ASN):
• For a 2-byte ASN, the RT type is set to 0200 (Type 0 in RFC 4364). The RT value is encoded in the format described in section 5.1.2.1
of RFC 8365: 2-octet-ASN: 4-octet-number, where the following values are used in the 4-octet-number eld:
VXLAN
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