Lacp Offload - Cisco Nexus 1000V Deployment Manual

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Figure 34.

Standard PortChannel Configuration

Standard PortChannels can be spread across more than one physical switch if the physical switches are

clustered. Examples of clustered switching technology include the Cisco Catalyst

6500 Virtual Switching System

1440, virtual PortChannels on the Cisco Nexus 7000 Series Switches, and the Cisco Catalyst Blade Switch 3120

for HP. Clustered switches act as a single switch and therefore allow the creation of EtherChannels across them.

This clustering is transparent to the Cisco Nexus 1000V. When the upstream switches are clustered, the Cisco

Nexus 1000V Switch should be configured to use LACP with one port profile, using all the available links. This

configuration will make more bandwidth available for the virtual machines and accelerate Live Migration.

LACP Offload

Traditionally, LACP is processed on the control plane of a switch (the supervisor or VSM). Because the Cisco

Nexus 1000V has a distributed model in the virtualization environment, new problems may arise when LACP is run

on the VSM in this way.

For example, if the VEM operates without the presence of the VSM, also referred to as headless mode, whenever

a link flap or reboot of the VEM occurs and there is no communication between the VEM and VSM, an LACP

bundle will not form. The bundle will not form because the VSM is responsible for originating and processing the

LACP control packets, also referred to as LACP protocol data units (PDUs), needed to negotiate an LACP

PortChannel.

Another situation with a similar problem may occur if the VSM is hosted (as a virtual machine) behind the VEM

and remote storage is used in an FCoE deployment. In an FCoE deployment, the virtual Fibre Channel (vFC)

interface is bound to the Ethernet LACP PortChannel.

For the VSM virtual machine to boot, this vFC interface needs to be up so that the remote storage can be

accessed. However, because the VSM is responsible for originating and processing the LACP PDUs, a

PortChannel cannot be formed because the VSM is not up at the start.

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