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Nexus 1000V - VEM & VSM Communication


as i understand the communication between the VSM and the VEM's can be over L3 and not just L2.

i need to understand what protocols are running between these two entities ? is it a 2-way communication?, meaning that the vsm is initiate the sessions and also the VEM initiate a sessions ?

do you have a detailed document about it ?

appreciate your help,


Cisco Employee

Re: Nexus 1000V - VEM & VSM Communication

Over Layer 2: If the VSM and the VEM are in the same Layer 2 domain, the best way to connect them is to use the Layer 2 connectivity mode:

Nexus1000V(config-svs-domain)# svs mode L2

• Over Layer 3: If the VSM and the VEM are in different Layer 2 domains, the Layer 3 connectivity mode should be used:

Nexus1000V(config-svs-domain)# svs mode L3

The Layer 3 mode will encapsulate the packet of the Layer 2 mode using Generic Routing Encapsulation (GRE). This process requires configuration of a VMware VMkernel interface on each VMware ESX host. This VMware VMkernel interface will need to be configured and attached to a port profile with the l3control option.

Nexus1000V(config)# port-profile type vethernet L3vmkernel

Nexus1000V(config-port-profile)#capability l3control

The l3control configuration tells the VEM that it can use this interface to send Layer 3 packets, so even if the Cisco Nexus 1000V Series is a Layer 2 switch, it can send IP packets.

Regardless of the mode of communication between the VSM and the VEM, after the VSM recognizes the VEM, a new module will be virtually inserted into the Cisco Nexus 1000V Series Switch's virtual chassis. The VSM CLI will notify the network administrator that a new module has powered on, much as with a physical chassis.
Extracted from above link.
Please follow the Cisco N1Kv reference and configuration guides for more details.
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