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Cisco Nexus 1000V Series Network Design
This section discusses design considerations related to Cisco Nexus 1000V Series connectivity to the physical
access layer.
Network Design Considerations
Multiple design considerations must be addressed when deploying the Cisco Nexus 1000V Series. At a basic level,
the design principles used when connecting the Cisco Nexus 1000V Series to a physical access layer are similar to
those used when connecting two physical switches together. Some design considerations are specific to the Cisco
Nexus 1000V Series. More than likely, each VEM will be connected to two access layer switches. Dual access switch
designs are the focus of this section.
Design Goals
A Cisco Nexus 1000V Series network design has two primary goals. First, the network should be designed for high
availability. In practical terms, such a design limits single points of failure where possible. VMware ESX provides
robust features to the server administrator to help ensure virtual machine availability. The Cisco Nexus 1000V Series
is responsible for network availability. Availability is usually facilitated by redundant links between each VEM and the
physical network, enabling the network to recover from link or physical switch failure.
The second design goal is to account for the uniqueness of VMware traffic patterns and the performance
requirements of the virtual machines. Each VMware ESX host generates and receives several classes of traffic, each
with unique characteristics. Network administrators must prioritize traffic to help ensure switch uptime, application
performance, and proper VMware capabilities.
Traffic Classification
Classification of traffic types in any network is not easy to achieve. In a VMware environment, traffic varies based on
the types of applications being virtualized. However, some traffic types can be identified and general prioritization
applied. The general classifications of traffic for a typical VMware deployment are as follows:
Control traffic: Control traffic is generated by the Cisco Nexus 1000V Series and exchanged between the
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primary and secondary VSMs as well as the VSMs and VEMs. It requires very little bandwidth (less than 10
KBps) but demands absolute priority. Control traffic is crucial to the Cisco Nexus 1000V Series' ability to
function properly, and its importance cannot be overstated. Control traffic should be considered the most
important traffic in a Cisco Nexus 1000V Series network.
Virtual machine data traffic: Data traffic is a generalization of all traffic transmitted or received by virtual
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machines. In an VMware ESX host, this is the primary traffic type. For obvious reasons, data traffic requires
high priority. The VSM management interface falls within this category.
VMware ESX management traffic: VMware vCenter Server requires access to the VMware ESX
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management interface to monitor and configure the VMware ESX host. Management traffic usually has low
bandwidth requirements, but it should be treated as high-priority traffic.
VMware VMmotion traffic: VMware VMotion traffic does not occur on a constant basis, meaning that most of
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the time VMware VMotion does not use any bandwidth. When VMware VMotion is initiated, it usually
generates a burst of data over a period of 10 to 60 seconds. VMware VMotion is not bandwidth sensitive.
When this type of traffic is faced with bandwidth that is lower than line rate, the duration of the virtual machine
move event is extended based on the amount of bandwidth available. Despite its popularity as a feature,
VMware VMotion traffic can usually be considered of medium priority relative to other traffic types.
Packet traffic: Packet traffic is used to transport selected packets to the VSM for processing. The bandwidth
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required for packet interface is extremely low, and its use is very intermittent. If Cisco Discovery Protocol and
IGMP features are turned off, there is no packet traffic at all. The importance of this interface is directly related
© 2009 Cisco Systems, Inc. All rights reserved. This document is Cisco Public Information.
Deployment Guide
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