Note: if you have been following my series on CCIE Voice / CCVP Exam Objectives, and are wondering why that series has stopped, don't worry because it hasn't. I'll be alternating between subjects over the next few weeks and months - and there will be plenty more on CCIE Voice / CCVP Exam objectives.
When the Nexus 7000 switch was introduced, one of its major features trumpeted by Cisco was virtualization in the form of Virtual Device Contexts (VDCs). But what exactly are VDCs, and how might they help you in your network?
You are probably already familiar with other forms of virtualization on switches such as Virtual LANs (VLANs) and more recently the Cisco 6500 Virtual Switching System 1440 (VSS 1440), but VDCs take virtualization on an individual switch to a new level. In this blog post, I'll take a look at what VDCs actually are, how they are configured, and how they can be used in real world networks.
VDCs, simply put, are a method of provisioning virtual Nexus switches. So, if you configure three VDCs on your Nexus switch, you'll have three virtual switches.
‘Very nice', you might be thinking, ‘but what happens if one of those virtual switches (VDCs) running on the same physical Nexus platform starts to misbehave?' Well, the other virtual switches just continue to operate normally. This is because each VDC has its own independent processes (OSPF, Spanning Tree, and so on), and NX-OS (the operating system that runs on the Nexus) is based on Linux. Linux has a pre-emptive scheduler that prevents a misbehaving process impacting the performance of the processes belonging to other VDCs. So, faults in one VDC will not impact the performance of another VDC.
Now that you have an understanding of what VDCs are and how they operate, it's time to take a look at how they can be configured.
It is possible to create a VDC and allocate resources using three simple steps:
You can verify VDC configuration using a number of commands such as show vdc vdcname and show vdc vdcname membership.
Here's an example of the configuration and verification of a VDC:
Mark-Nexus01(config)# vdc TestVDC2
Note: VDC creation is a time consuming process, please wait until the command completes
Mark-Nexus01(config-vdc)# allocate interface ethernet 10/1-12
Moving ports will cause all config associated to them in source vdc to be removed. Are you sure you want to move the ports? [yes]
Mark-Nexus01(config-vdc)# show vdc TestVDC2
vdc_id vdc_name state mac
------ -------- ----- ----------
2 TestVDC2 active 00:1b:54:c2:29:42
Mark-Nexus01(config-vdc)# show vdc TestVDC2 membership
vdc_id: 2 vdc_name: TestVDC2 interfaces:
Ethernet10/1 Ethernet10/2 Ethernet10/3
Ethernet10/4 Ethernet10/5 Ethernet10/6
Ethernet10/7 Ethernet10/8 Ethernet10/9
Ethernet10/10 Ethernet10/11 Ethernet10/12
Mark-Nexus01# switchto vdc TestVDC2
---- System Admin Account Setup ----
Enter the password for "admin":
Confirm the password for "admin":
---- Basic System Configuration Dialog VDC: 2 ----
This setup utility will guide you through the basic configuration of
the system. Setup configures only enough connectivity for management
of the system.
Please register Cisco Nexus7000 Family devices promptly with your
supplier. Failure to register may affect response times for initial
service calls. Nexus7000 devices must be registered to receive
entitled support services.
Press Enter at anytime to skip a dialog. Use ctrl-c at anytime
to skip the remaining dialogs.
Would you like to enter the basic configuration dialog (yes/no): n
Cisco Nexus Operating System (NX-OS) Software
TAC support: http://www.cisco.com/tac
Copyright (c) 2002-2008, Cisco Systems, Inc. All rights reserved.
The copyrights to certain works contained in this software are
owned by other third parties and used and distributed under
license. Certain components of this software are licensed under
the GNU General Public License (GPL) version 2.0 or the GNU
Lesser General Public License (LGPL) Version 2.1. A copy of each
such license is available at
Mark-Nexus01-TestVDC2# conf t
Mark-Nexus01-TestVDC2(config)# int mgmt 0
Mark-Nexus01-TestVDC2(config-if)# ip addr 10.1.1.1 255.255.255.0
So, all pretty simple.
At this point you might be saying to yourself, ‘Nice feature, but what can I actually use it for?'.
Here are four initial usage scenarios:
1. Migration: if you are migrating to a new infrastructure, VDCs can be a very useful way of isolating different parts of your network during that migration.
2. Topology and device consolidation: VDCs allow you to virtualize different layers of a multilayer switched network. So, you could, for example, have a Nexus that performs both distribution and core layer functions, and has physical wiring between the interfaces allocated to the distribution VDC (virtual distribution layer switch) and core VDC (virtual core layer switch) that are on the same physical switch.
3. Hosting: if you are operating a secure hosting environment, VDCs can allow you to virtualize your network infrastructure and offer required isolation on shared physical Nexus switches.
4. Independent operation and security zoning: VDCs can allow different parts or units of a business that require independent operation and security zoning to share the same physical Nexus switches.
As I mentioned above, these are just four initial VDC usage scenarios. As Nexus deployments become more widespread, users will inevitably come up with their own ways of using VDCs.
So, in summary, VDCs are a very useful feature of the Nexus switches.
Mark Lewis (CCIE#6280) is an independent consultant who helps service provider and large enterprise clients design and implement leading-edge technologies. Over the last couple of years, Mark has designed and implemented a variety of large-scale technology solutions including VPN, MPLS, QoS, data center, and IP telephony. Mark is the author of three books for Cisco Press: Comparing, Designing, and Deploying VPNs, Troubleshooting Virtual Private Networks, and CCIE Voice Exam Quick Reference Sheets.