Control Plane - Cisco Nexus 7000 Series Configuration Manual

VXLAN BGP EVPN and OTV Interoperation
In DC-1 and DC-2, there are 2 scenarios where Layer 2 traffic is transported between VXLAN and OTV
overlays or tunnels. On the border leaf switch, traffic from the VXLAN fabric is either sent to a server within
the datacenter, or towards another datacenter through OTV. The other way around, the border leaf switch
receive traffic from OTV towards the VXLAN fabric or CE pod. When you configure this feature, Layer 2
traffic seamlessly passes between the VXLAN and OTV tunnels on the same device. Packet flow details in
DC-1 and DC-2:
• Packet flow within the Layer 2 CE pod and packet flow within the VXLAN BGP EVPN pod (see
• When a VXLAN+OTV border leaf switch receives traffic from another site over OTV, it removes the
• When a server in the VXLAN BGP EVPN fabric sends traffic to a server in the Layer 2 CE pod, the
Packet flow details in DC-4:
• When a Layer 2 CE pod server in the datacenter with the OTV+BDI one box solution sends traffic, the
• When the Layer 3 OTV (with BDI) switch receives traffic from another datacenter over OTV, it OTV

Control Plane

• BGP EVPN is used for advertising MAC and MAC-IP routes across the VXLAN BGP EVPN fabric in
"Configuring VXLAN BGP EVPN" chapter) remains the same. When a Layer 2 CE pod server sends
traffic to a server in the VXLAN fabric within the site or to another site, the packets reach the border
leaf switch. The bridge domain, Layer 2/Layer 3 VNI mappings, and MAC routes of the VXLAN fabric
are available in the border leaf switch. If the destination server is within the fabric, the border leaf switch
VXLAN encapsulates the packet and sends it to the corresponding ToR or leaf switch. The leaf switch
VXLAN decapsulates the traffic and sends the original packet to the intended server. If the destination
server is in another site, the border leaf switch OTV encapsulates the traffic towards the remote site.
Though the simplified sample topology depicts a single switch at the ToR/leaf layer
Note
carrying Layer 2 server traffic within the VXLAN BGP EVPN fabric, a real time VXLAN
fabric spine-leaf setup will have multiple switches at the ToR/leaf and spine layers, and
intra fabric Layer 2 server traffic flows through those non border leaf switches.
OTV encapsulation, does a lookup to find out where the destination server resides, and VXLAN
encapsulates the traffic towards the corresponding ToR/leaf switch. The leaf switch VXLAN decapsulates
the traffic and sends the original packet to the intended server. If the destination server is in the Layer
2 CE pod, the border leaf switch OTV decapsulates the traffic and sends the traffic to the destination
server without any encapsulation.
border leaf switch receives the packets. It VXLAN decapsulates the traffic and sends it to the destination
server in the CE pod.
destination server is either within the datacenter or outside of it. Traffic flow within the datacenter
remains the same. If the destination server is in another site, then the packets reach the Layer 3 OTV
(with BDI) switch. The switch OTV encapuslates the traffic towards the legacy or VXLAN+OTV
datacenter. The border switch in the destination datacenter receives the traffic, OTV decapsulates it, and
forwards it as explained in the earlier sections.
decapsulates the traffic and sends it towards the corresponding Layer 2 access switch. The access switch
forwards the packets to the destination server.
DC-1 and DC-2.
Cisco Nexus 7000 Series NX-OS VXLAN Configuration Guide
Control Plane
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