Cisco Nexus 1000V Deployment Manual - Page 12

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Also for Cisco Nexus 1000V: Deployment Manual (49 pages), Datasheet (8 pages), Manual (6 pages), Installing Manual (27 pages)

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Deployment Guide

expected to require 10 to 50 MB of RAM, with an upper hard limit of 150 MB for a fully scaled solution with all

features turned on and utilized to their design limits.

Each instance of the Cisco Nexus 1000V Series is composed of two VSMs and one or more VEMs. The maximum

number of VEMs supported by a pair of VSMs is 64.

Switch Port Interfaces

The Cisco Nexus 1000V Series supports multiple switch port types used for internal and external connectivity: virtual

Ethernet (vEth), Ethernet (Eth), and PortChannel (Po). The most common port type within a Cisco Nexus 1000V

Series environment is a new concept called a virtual Ethernet interface. This interface type represents the switch port

connected to a virtual machine's vNIC or connectivity to specialized interface types such as the vswif or vmknic

interface.

A vEth interface has several characteristics that differentiate it from other interface types. Besides the obvious fact

that vEth interfaces are virtual and therefore have no associated physical component, the interface naming

convention is unique. Unlike a traditional Cisco interface, a vEth interface's name does not indicate the module with

which the port is associated. Whereas a traditional physical switch port may be notated as GigX/Y, where X is the

module number and Y is the port number on the module, a vEth interface is notated like this: vEthY. This unique

notation is designed to work transparently with VMotion by keeping the interface name the same regardless of the

location of the associate virtual machine.

The second characteristic that makes a vEth interface unique is its transient nature. A given vEth interface may

appear or disappear based on the status of the virtual machine connected to it. The mapping of a virtual machine's

vNIC to a vEth interface is static. When a new virtual machine is created, a vEth interface is also created for each of

the virtual machine's vNICs. The vEth interfaces will persist as long as the virtual machine exists. If the virtual

machine is temporarily down (the guest OS is shut down), the vEth interfaces will remain inactive but still bound to

that specific virtual machine. If the virtual machine is deleted, the vEth interfaces will become available for connection

to newly provisioned virtual machines.

The Cisco Nexus 1000V Series contains two interface types related to the VMNICs (physical NICs) within a VMware

ESX host. An Ethernet, or Eth, interface is the Cisco Nexus 1000V Series' representation of a VMNIC. An Eth

interface is represented in standard Cisco interface notation (EthX/Y) using the Cisco NX-OS naming convention

"Eth" rather than a speed such as "Gig" or "Fast," as is the custom with Cisco IOS Software. These Eth interfaces are

module specific and are designed to be fairly static within the environment.

PortChannels are the third interface type supported by the Cisco Nexus 1000V Series. A PortChannel is an

aggregation of multiple Eth interfaces on the same VEM.

Note:

PortChannels are not created by default and must be explicitly defined.

Switch Forwarding

In many ways the Cisco Nexus 1000V Series Switches are similar to physical Ethernet switches. For packet

forwarding, the Cisco Nexus 1000V Series uses the same techniques that other Ethernet switches apply, keeping a

MAC address–to–port mapping table used to determine where packets should be forwarded.

The Cisco Nexus 1000V Series maintains forwarding tables in a slightly different manner than other modular

switches. Unlike physical switches with a centralized forwarding engine, each VEM maintains a separate forwarding

table. There is no synchronization between forwarding tables on different VEMs. In addition, there is no concept of

forwarding from a port on one VEM to a port on another VEM. Packets destined for a device not local to a VEM are

forwarded to the external network, which in turn may forward the packets to a different VEM.

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