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Nexus 1000v Switch - VSM and VEM Connectivity Issues

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Introduction

This document describes about communication issues between Nexus 1000v VSM and VEM, which are frequently occuring and sometimes difficult to troubleshoot. The VSM is the control software of the Cisco Nexus 1000V distributed virtual switch. It runs on a virtual machine (VM) and is based on Cisco NX-OS software. The external Virtual Supervisor Module (VSM) manages the Cisco Nexus 1000V Series switch VEMs. The VEM is the part of Cisco Nexus 1000V that actually switches data traffic. The Virtual Ethernet Module (VEM) executes inside the Cisco Nexus 1000V Series switch hypervisor. A set of dual redundant VSMs and managed VEMs form a single Nexus 1000v switch domain.

 

 

About VSM and VEM

 

Cisco Nexus 1000V has 2 parts:

Virtual supervisor module (VSM) - This is the control software of the Cisco Nexus 1000V distributed virtual switch. It runs on a virtual machine (VM) and is based on NX-OS software.
Virtual Ethernet module (VEM) - This is the part of Cisco Nexus 1000V that actually switches data traffic. It runs on a VMware ESX 4.0 host. Several VEMs are controlled by one VSM. All the VEMs that form a switch domain should be in the same virtual Data Center as defined by VMware VirtualCenter.

 

Troubleshoot Connectivity Issues

 

1. Ensure that CONTROL and PACKET VLAN are properly trunked

 

Ensure that on each switches lying between the VEM and VSM the Layer 2 Communication VLAN is allowed on the trunk and is configured.

 

switchport trunk allowed vlan 310

 

In this example, VLAN 310 is the Control VLAN for L2 Communication, same holds good for the PACKET VLAN as well.

This is one of the major task in troubleshooting the L2 Connectivity issue and resolves the issue 90% of the times if other configuration on Nexus 1000v are good.

 

2. Check VSM and vCenter Configuration

 

Following commands help troubleshoot vCenter and VSM Configuration

show vmware vc extension-key

 

To check VSM to VCENTER Sync status:

show svs domain

show vmware vc extension-key

 

Checking opaque data in VSM :

show svs domain

 

Checking Opaque Data in VEM :

vemcmd show card

 

3. Troubleshooting Layer 2 Issues

 

Following command can be used to check L2 connectivity issue

vem-health check VSM_CTRL_MAC_ADDR

 

To find the Control MAC Address you can use the following command:

show interface control 0

 

Check if the VEM's upstream switch has learned the VSM's Control MAC. Please note that on the Uplink port profile should have CONTROL and PACKET VLAN and must be defines as system VLAN.

 

Related Information

Nexus 1000V Recovery from Failed VEM

ESX and ESXi Commands to troubleshoot Nexus 1000v on UCS

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