One of the topics that will be so fun to tackle in Session 2 of the 8 session CCIE Data Center Written Exam Blueprint will be Virtual Device Contexts (VDCs) of the Cisco Nexus 7000 series. Sure, the device can do wonders with the preexisting virtualization technologies like VLANs at Layer 2 and VRFs at Layer 3, but the Cisco Nexus 7000 leaps beyond these capabilities to actually virtualize itself as shown in the diagram here.
The device actually presents its own physical self as multiple logical units – each fully independent (or real close!) of each other.
The virtualization capabilities attack numerous planes – including:
- Control plane – for multiple logical topologies and fault domains
- Data plane – permitting data segregation
- Management plane – for administrative segregation
- Software partitioning - for the formation of well-defined fault domains
- Hardware components – permitting the predicable allocation of hardware resources
Often times I will overhear my peers commenting – “big deal! – we have had this in the Cisco ASA security devices for years!” – well, be careful now, as there is certainly virtualization of the physical device there into logical partitions, but it remains at strictly the configuration, management, and data plane levels.
In the default state, the switch control plane runs a single device context named VDC 1 that runs approximately 80 processes. Some of these will spawn other processes resulting in as many as 250 running at any one given time. This collection of processes constitutes the control plane for a single physical device if all you ever implement is this default context. If you remained at this state, your virtualization would indeed be limited to the VLAN and VRF capabilities.
When we create additional Virtual Device Contexts (VDCs), all of these processes are replicated for each device context created. Duplication of VRF names and VLAN IDs is now possible as each VDC is its own virtual switch.
Scalability is enormous with four thousand VLANs capable per VDC, two hundred and fifty six VRFs per VDC, and four VDCs capable in all. Note that the default VDC is one of these four.
Thanks to this capability in the Nexus 7000 series device – fault isolation, administration, data traffic handling, and secure are all dramatically enhanced.
We hope you will join us as we examine these configurations in much greater detail!
Anthony Sequeira CCIE, CCSI