Realizing Layer-2 And Layer-3 Multi-Tenancy - Cisco Nexus 7000 Series Configuration Manual

Realizing Layer-2 and Layer-3 Multi-Tenancy

• End host to ToR mapping information for each ToR is shared with every other ToR using BGP via a
• Specifically, within BGP, the EVPN address family is employed to carry MAC and IP address information
• VMs belonging to the same tenant might be many hops apart (though assigned with the same segment
• In order to accurately route/switch packets between end hosts in the data center, each participating ToR
VXLAN-EVPN fabric— The overlay protocol is VXLAN and BGP uses EVPN as the address family for
communicating end host MAC and IP addresses, so the fabric is referred thus.
Realizing Layer-2 and Layer-3 Multi-Tenancy
Using segment IDs or VNIs for multi tenancy in the VXLAN fabric
Typically, when a tenant is created, it is assigned a unique VNI referred to as the layer-3 VNI or the layer 3
segment ID. This serves as a unique identifier for tenant layer-3 context also referred to as the tenant VRF.
For each network created within the tenant, a unique identifier is assigned which is referred to as the layer-2
VNI or layer-2 segment-id. The VNIs all come from the same 2^24 – 1 pool represented by the 24-bit VNI
identifier carried in the VXLAN header.
Figure 5: VXLAN Packet Format
Some Segment ID/VNI pointers are given below:
• If a new VM or physical server for this tenant is added to the data center, it is associated with the same
• By confining server and end host identification of a specific tenant to a unique VNI (or few unique
• By ensuring that the VNI-to-end host mapping information on each ToR is updated and shared through
• Routing at the ToR/access layer facilitates a more scalable design, contains network failures, and enables
Traffic between servers in the same tenant network that is confined to the same subnet is bridged. In this case,
the VTEPs stamp the layer-2 VNI in the VXLAN header when the communication is between servers that
Cisco Nexus 7000 Series NX-OS VXLAN Configuration Guide
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route reflector.
of the end hosts along with other information such as the network and tenant (aka VRF) to which they
belong. This allows optimal forwarding of both layer-2 and layer-3 traffic within the fabric.
ID/VNI), and there might be frequent movement and addition of end hosts. When a new VM comes up
or is moved between ToRs, the information is instantly updated into BGP by the detecting ToR thereby
ensuring that the updated reachability information is also known to every other ToR.
in a VXLAN cluster must be aware of the end hosts attached to it and also the end hosts attached to
other ToRs, in real time.
layer-3 VNI, regardless of the physical location. In addition, if it is part of a given tenant network, it is
assigned the same layer-2 VNI that identifies that network.
VNIs), segmentation and security are ensured.
the route reflector, the latest information is available through the VXLAN setup.
transparent mobility.
Configuring VXLAN BGP EVPN