Layer 3 Unicast Routing - Cisco Nexus 7000 Series Configuration Manual

Layer 3 Unicast Routing

• Intermediate-System to Intermediate-System (IS-IS) is used for advertising MAC routes across OTV
• MAC Route updates in the control plane are reflected across the OTV and VXLAN tunnels.
Layer 3 Unicast Routing
DC-1 and DC-2 (VXLAN BGP EVPN fabric)
Layer 3 routing within the VXLAN BGP EVPN fabric takes place through an underlay Interior Gateway
Protocol (IGP) such as Intermediate System-to-Intermediate System (IS-IS) or OSPF.
Layer 3 traffic between the border leaf switches and the IP WAN should be through over Multiprotocol Label
Switching (MPLS) L3VPN or virtual routing and forwarding (VRF) Lite. The IGP and external connectivity
documentation is available in the Cisco Programmable Fabric with VXLAN BGP EVPN Configuration Guide.
A distributed anycast gateway (or BDI) IP address is used for Layer 3 traffic between Layer 2 virtual networks
in the VXLAN fabric. This should be configured as the secondary BDI IP address. A unique, primary gateway
IP address should be configured on each BDI for sending ARP requests over OTV. Packet flow details in
DC-1 and DC-2:
• Though the main focus of the feature is one box solutions for VXLAN+OTV with BDI and OTV
Note
• Though the simplified sample topology depicts a border leaf switch carrying Layer 3 server traffic
• When a server in the Layer 2 CE pod sends traffic to a server in another VLAN/subnet, either located
• When the Layer 3 DCI enabled border switch receives Layer 3 traffic from another site (through MPLS
DC-3, the legacy datacenter
• Layer 3 routing within DC-3 is through an IGP implemented on the aggregation switches. A Layer 3
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configured device.
with BDI functions, traffic flow from/to the Layer 2 CE pod is also explained for completeness.
within the VXLAN BGP EVPN fabric, real time intra VXLAN fabric server traffic flow is through
a non border leaf switch.
in the VXLAN BGP EVPN fabric within the site or to a server in a remote site, the traffic first reaches
the border leaf switch. The bridge domain, Layer 2/Layer 3 VNI mappings, MAC routes and the
appropriate IGP configuration will be available in the border leaf switch. If the destination server is
within the fabric, the border leaf switch VXLAN encapsulates the packet and routes it to the corresponding
ToR or leaf switch through the fabric underlay routing protocol such as IS-IS or OSPF. 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 sends the traffic towards the remote site through a Layer
3 DCI technology like MPLS L3VPN or OTV, depending on how the host route is learnt (through MPLS
VPN or OTV).
VPN or OTV), it does a lookup to find out where the destination server resides and routes the packets
(across VLANs, through the corresponding destination BDI), to the corresponding Layer 2 switch. The
switch forwards the packets to the intended destination server.
Hot Standby Router Protocol (HSRP) gateway with First Hop Redundancy Protocol (FHRP) filtering
should be configured.
VXLAN BGP EVPN and OTV Interoperation