Fabric Overlay Control-Plane (Mp-Bgp Evpn) - Cisco Nexus 7000 Series Configuration Manual

Configuring VXLAN BGP EVPN
are below different ToRs. The forwarding lookup is based on (L2-VNI, DMAC). For communications between
servers that are part of the same tenant but belong to different networks, routing is employed. In this case, the
layer-3 VNI is carried in the VXLAN header when communication is between servers below different ToRs.
This approach is referred to as the symmetric IRB (Integrated Routing and Bridging) approach, the symmetry
comes from the fact that VXLAN encapsulated routed traffic in the fabric from source to destination and
vice-versa will carry the same layer-3 VNI. This is shown in the figure below.
Figure 6: Inter Tenant Traffic Flow Using VRF VNI
In the above scenario, traffic from a server (with layer-2 VNI x) on VTEP V1 is sent to a server (with layer-2
VNI y) on VTEP V2. Since the VNIs are different, the layer-3 VNI (unique to the VRF) is used for
communication over VXLAN between the servers.

Fabric Overlay Control-Plane (MP-BGP EVPN)

The main reasons for using BGP EVPN as the overlay control plane are:
• Standards based—The overlay (VXLAN) and the control plane (BGP) are standards based.
• Implement control-plane MAC learning so that VMs/servers for each tenant have a unique identity across
the fabric.
In a VXLAN-EVPN based fabric, MAC learning occurs via the control plane [through multi-protocol
(MP) BGP] instead of the data plane.
When a new end host is attached to a VTEP (aka ToR), the VTEP advertises the MAC and IP address
of the end host to a route reflector which in turn advertises it to the other VTEPs through MP-BGP (as
Fabric Overlay Control-Plane (MP-BGP EVPN)
Cisco Nexus 7000 Series NX-OS VXLAN Configuration Guide
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