Cisco Nexus 1000V Switch Features; Switch Forwarding; Mac Address Learning - Cisco Nexus 1000V Deployment Manual

Switch for microsoft hyper-v

Hide thumbs Also See for Nexus 1000V:

Table of Contents

Cisco Nexus 1000V Switch Features

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

the Cisco Nexus 1000V Switch uses the same techniques that other Ethernet switches apply, with a MAC

address-to-port mapping table used to determine the location to which packets should be forwarded.

The Cisco Nexus 1000V Switch 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.

This distributed forwarding model in a centrally managed switch is demonstrated by the way the Cisco Nexus

1000V handles MAC address learning. A MAC address can be learned multiple times within a single Cisco Nexus

1000V Switch in either of two ways: statically or dynamically. Static entries are automatically generated for virtual

machines running on the VEM; these entries do not time out. For devices not running on the VEM, the VEM can

learn a MAC address dynamically, through the pNICs in the server.

Each VEM maintains a separate MAC address table. Thus, a single Cisco Nexus 1000V Switch may learn a given

MAC address multiple times: as often as once per VEM. For example, one VEM may be hosting a virtual machine,

and the virtual machine's MAC address will be statically learned on the VEM. A second VEM, in the same Cisco

Page 26 of 48

Table of Contents