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Cisco Nexus 7000 Series NX-OS Unicast Routing Configuration Guide, Release 4.x
OL-20002-02
Chapter 1 Overview
Layer 3 Virtualization
OSPF is an example of a link-state protocol.
Layer 3 Virtualization
Cisco NX-OS introduces the virtual device context (VDC), which provides separate management
domains per VDC and software fault isolation. Each VDC supports multiple Virtual Routing and
Forwarding Instances (VRFs) and multiple routing information bases (RIBs) to support multiple address
domains. Each VRF is associated with a routing information base (RIB) and this information is collected
by the Forwarding Information Base (FIB). Figure 1-3 shows the relationship between VDC, VRF, and
the Cisco NX-OS system.
Figure 1-3 Layer 3 Virtualization Example
A VRF represents a layer 3 addressing domain. Each layer 3 interface (logical or physical) belongs to
one VRF. A VRF belongs to one VDC. Each VDC can support multiple VRFs. For more information,
see Chapter 14, “Configuring Layer 3 Virtualization.”
See to the Cisco Nexus 7000 Series NX-OS Virtual Device Context Configuration Guide, Release 4.x for
details on VDCs.
Cisco NX-OS Fowarding Architecture
The Cisco NX-OS forwarding architecture is responsible for processing all routing updates and
populating the forwarding information to all modules in the chassis.
This section includes the following topics:
• Unicast RIB, page 1-11
• Adjacency Manager, page 1-11
• Unicast Forwarding Distribution Module, page 1-12
• FIB, page 1-12
Cisco NX-OS System
VDC 1 VDC n
Routing
Protocol VRF
Routing Protocol
Routing
Protocol VRF
RIBs
RIB table RIB table
VRF n
VRF 1
RIBs
RIB table RIB table
Forwarding Information Bases
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