Specifications

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11-2
Cisco Nexus 3000 Series NX-OS Unicast Routing Configuration Guide, Release 5.0(3)U2(2)
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Chapter 11 Configuring Layer 3 Virtualization
Layer 3 Virtualization
Each router has a default VRF and a management VRF. All Layer 3 interfaces and routing protocols exist
in the default VRF until you assign them to another VRF. The mgmt0 interface exists in the management
VRF.With the VRF-lite feature, the switch supports multiple VRFs in customer edge (CE) switches.
VRF-lite allows a service provider to support two or more Virtual Private Networks (VPNs) with
overlapping IP addresses using one interface.
Note The switch does not use Multiprotocol Label Switching (MPLS) to support VPNs.
VRF and Routing
All unicast and multicast routing protocols support VRFs. When you configure a routing protocol in a
VRF, you set routing parameters for the VRF that are independent of routing parameters in another VRF
for the same routing protocol instance.
You can assign interfaces and route protocols to a VRF to create virtual Layer 3 networks. An interface
exists in only one VRF. Figure 11-1 shows one physical network split into two virtual networks with two
VRFs. Routers Z, A, and B exist in VRF Red and form one address domain. These routers share route
updates that do not include router C because router C is configured in a different VRF.
Figure 11-1 VRFs in a Network
By default, Cisco NX-OS uses the VRF of the incoming interface to select which routing table to use for
a route lookup. You can configure a route policy to modify this behavior and set the VRF that Cisco
NX-OS uses for incoming packets.
Cisco NX-OS prevents route leakage(import or export) between VRFs.
VRF-Lite
VRF-lite is a feature that enables a service provider to support two or more VPNs, where IP addresses
can be overlapped among the VPNs. VRF-lite uses input interfaces to distinguish routes for different
VPNs and forms virtual packet-forwarding tables by associating one or more Layer 3 interfaces with
each VRF. Interfaces in a VRF can be either physical, such as Ethernet ports, or logical, such as VLAN
SVIs, but a Layer 3 interface cannot belong to more than one VRF at any time.
Note Multiprotocol Label Switching (MPLS) and MPLS control plane are not supported in the VRF-lite
implementation.
Note VRF-lite interfaces must be Layer 3 interfaces.
Ethernet 1/1
VRF Red
Ethernet 2/1
VRF Red
Ethernet 2/2
VRF Blue
Router Z
Router A
Router B
Router C
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