Nexus 1000v

Cisco Nexus 1000v

I am writing this blog to mention below key components/terms/definitions related to Nexus 1000v

What is a hypervisor?
Hypervisor is a program that allows multiple OS to share single hardware host

Basic Building Blocks

– It is the control/management plane of 1000v

– Data Plane

Traffic flow with VSM and VEM:
Traffic flow from VEM northbound does not go through VSM.

The physical NICs on the VEM server are uplinks to the external fabric. VEMs switch traffic between the local virtual Ethernet ports connected to VM vNICs, but do not switch traffic to other VEMs. Instead, a source VEM switches packets to uplinks that the external fabric then delivers to the target VEM. The VSM runs the control plane protocols and configures the state of each VEM, but it never takes part in the actual forwarding of packets.
A single VSM can control up to 64 VEMs

VSM Deployment
VSMs are ideally deployed as a pair with active and redundant VSM.
So even if the primary VSM fails, the backup VSM can take over.
Does disruption in VSM to VEM communication affect virtual machine traffic?

So how does Nexus 1000v compare to a modular Cisco switch?
Primary VSM——————-Supervisor
Backup  VSM——————-Redundant supervisor
VEM 1—————————–Line Card 1
VEM 2 —————————-Line Card 2
What are port profiles?
Port profile defines a set of attributes that can include the following:
b, Port channels
c. Private VLAN
d. ACL
e. Port security
f. NetFlow
g. rate limiting
h. QoS Marking
The network administrator defines port profiles in the VSM. When the VSM connects to vCenter Server, it creates a distributed virtual switch (DVS) and each port profile is published as a port group on the DVS. The server administrator can then apply those port groups to specific uplinks, VM vNICs,  or management ports, such as virtual switch interfaces or VM kernel NICs.

VEM Virtual Ports

Three types of vNIC in VMWare
1. Virtual NIC

2. vEth port
Represent a port on Nexus 1000v virtual switch.
These ports are assigned to port group.

3. lvEth port
Dynamically selected for vEth ports on the host.

Further, there are 3 types of Virtual NICs.
1. vnic
Part of the VM and represents the physical port of the host which is plugged into the switch

2. vmknic
Used by the hypervisor for management,VMotion,iSCSI,NFS and other network access needed by kernel.

3. vswif
VMWare service console network interface, the Service Console network interface.
The vswif interface is used as VMWare management port; these interface types map to a veth port within Nexus 1000v

VSM to VEM Communication

1. Layer 3 Control Mode

VEMs can be in different subnet than the VSM and also from each other in Layer 3 control mode.

Each VEM needs a designated VMkernel NIC interface that is attached to the VEM that communicates with the VSM.
This interface which is called Layer 3 Control vmknic must have a system profile applied to it so the VEM can enable it before contacting the VSM.

2. Layer 2 Control Mode

VEM and VSM are in the same subnet in the Layer 2 control mode.


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