Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 
Community Member

Nexus 1000V CPU usage - Lost connection


Sometimes, a VM lose network connection.

No problem where detected on the network to explain this problem.

This VM (running Windows Server 2003 R2) is connected through VMware flexible network adapter.

I verified all parameters in the running config of this virtual port : no difference with other VMs.

The only thing a noticed is when connections are lost, CPU usage of the VSM VM is about 60% (shown in vCenter performance charts), while the CPU usage is normally staying under 5%.

I look at the return of show log command in the VSM but nothing is logged about CPU usage or lost connection of the VEM.

How can I explaind and/or correct these loses of network connection ?

Thanks in advance.

Everyone's tags (3)
Cisco Employee

Nexus 1000V CPU usage - Lost connection


A few questions.

1. Version of 1000v and ESX

2. Only the one Win2k3 VM affected?

3. Have you tried the VMXNet3 driver?  It's the recommended one for Windows & 1000v.

4. When the issue occurs are the VSM and VM running on the same ESX host?

5. How frequently does the issue occur & any pattern?  (time of day etc)

The VSM doesn't really have much bearing on a VMs network operation.  Once the VEM the VM is running on has been programmed it should stay running fine, unless the VEM loses connectivity to the VSM, and you say this hasn't happend - correct?

Can you also attach the output of "show log" from the VSM, in & around the time you see the high CPU timestamps?



Community Member

Nexus 1000V CPU usage - Lost connection

Hi Robert.

Thanks for your help.


Nexus 1000V is running version 4.2(1)SV1(4).

ESX is running ESXi version 4.1U2.


The problem can appear on other VMs, but nothing tells me that a connection was lost on other VMs.


I did'nt tried VMXNET3, but it's planned to be done.

-> Where can I find bast practices and/or recommandations ?


When this happened, the VSM and the VM weren't running on the same host.


I can't attach show log because no messages were logged during the period of high CPU usage.



Cisco Employee

Nexus 1000V CPU usage - Lost connection

Some information on the various VM Network adaptor drivers here:

The VSM should have some record of the VM's network disruption, otherwise I would look the host utlization to see if there's anything in the vmkernel logs. 

Does this issue ever happen while the VM is on a vSwitch or just 1000v?

Any performance style issues can get pretty difficult to troubleshoot over a forum.  You might be best suited opening a TAC case so we can take a live look at your system.



CreatePlease to create content