Vlan Consistency; Traffic Separation; Upstream Switch Connectivity; Individual Uplinks - Cisco Nexus 1000V Series Deployment Manual

to the use of IGMP. If IGMP is not deployed, then this interface is used only for Cisco Discovery Protocol,
which is not considered a critical switch function.

VLAN Consistency

Proper VLAN configuration on the physical infrastructure is important to helping ensure that the Cisco Nexus 1000V
Series functions correctly. A VLAN defined on a physical switch has universal meaning: that is, every port on the
switch configured in VLAN 10 is in the same VLAN; there is no concept of two discreet VLANs with ID 10 on the
same switch. The same is true for the Cisco Nexus 1000V Series, but the switch architecture relies on proper
physical switch configuration to help ensure this consistency.
Multiple VEMs require a physical Ethernet switch for inter-VEM connectivity. Each VEM needs consistent connectivity
to all VLANs that are defined on the Cisco Nexus 1000V Series. Thus, any VLAN that is defined on the Cisco Nexus
1000V Series must also be defined on all upstream switches connected to each VEM.
Each VLAN should be trunked to each VEM using IEEE 802.1q trunking. Although not required, the uplink port
profiles should be consistently applied to each VEM.

Traffic Separation

Traditional VMware network design calls for a minimum of three VLANs trunked to the VMware ESX host. These
VLANs are used for virtual machine data, the VMware ESX service console, and VMkernel (VMware VMotion), with
optional VLANs used for IP-based storage or additional virtual machine connectivity. The Cisco Nexus 1000V Series
requires additional VLANs to support the control and packet interfaces.
The control and packet interfaces should be deployed on discreet VLANs, even though no configuration requirement
or CLI enforcement prevents the two interfaces from sharing the same VLAN. Deployment on discreet VLANs is
recommended for several reasons.
The control interface is much chattier and broadcast based than the packet interface. If the two interfaces were in the
same VLAN, the packet interface would receive unnecessary broadcast traffic. Also, although the packet interface is
important, the control interface is much more crucial to overall system function. Keeping the control interface isolated
from any external influence helps ensure reliable system operation.
Multiple Cisco Nexus 1000V Series Switches can share common VLANs for their respective control and packet
interfaces, but ideally each Cisco Nexus 1000V Series has separate VLANs. When the same control and packet
VLANs are shared across multiple Cisco Nexus 1000V Series Switches, take care to help ensure the uniqueness of
domain IDs.

Upstream Switch Connectivity

Much of the design work of a Cisco Nexus 1000V Series solution focuses on proper upstream switch connectivity.
Connecting a Cisco Nexus 1000V Series Switch to a physical switch is not unlike connecting two physical switches to
each other.
You can connect a Cisco Nexus 1000V Series Switch to a physical infrastructure in two ways: using standard uplinks
and using PortChannels.

Individual Uplinks

A standard uplink is an uplink that is not a member of a PortChannel from the VEM to a physical switch. It provides
no capability to load balance across multiple standard uplink links and no high availability characteristics. When a
standard uplink fails, no secondary link exists to take over. Defining two standard uplinks to carry the same VLAN
involves the risk of creating loops within the environment and is an unsupported configuration. Cisco NX-OS will issue
warnings when such a condition occurs.
© 2009 Cisco Systems, Inc. All rights reserved. This document is Cisco Public Information.
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