What is Nexus 1000v

1. Nexus 1000V (N1kv) is a distributed edge virtual switch leveraging NX-OS which extends the switch to the ESX host and essentially sits b/w the host & the upstream switch. 
2. It can be installed as a OVM (VM) on any host or as a physical appliance (Nexus1010).
3. It has a sup (VSM) which controls multiple line cards in a sense (VEM) installed on a single host.
4. Each host can only support one VEM and VSM can manage a max of 64 VEMs.

Below we have a 2 VSM modules connected to 2 upstream switches which are then connected bunch of VEMs installed in individual ESX hosts.

VSM allows configuration of::-

1. VLANs
2. ACL, PVLANs etc
3. Netflow, ERSPAN
4. QoS
5. Physical NIC port configuration

A vethernet interface is defined for each VMNIC on the VM and an ethernet interface is defined for each physical NIC port on the ESX host.

1. Each ethernet interface is assigned an uplink port profile to provide uplink(external) connectivity.
2. The n/w admin can create port profiles on the VSM (with some/all of above attributes) and assign a vethernet port to any one of these port-profiles.

The design of N1Kv prevents loops by tagging/recognizing/switching that veth traffic to VEMs and ethernet traffic to uplink port of the physical NIC.