I have deployed a ton of these on 4.x and just recently deployed a new 1000v farm on 5.1 so the version referenced here will be based on what was available on cisco.com at that time. Versioning is very important so you should ensure your network guys (in charge of the VSM) are on the same version you are shooting for. It's ok to have the VEM a bit behind the version of the VSM, but in general you want to keep them the same.
Download the following zip file from cisco.com (register for a instant free account, no serial# needed):
Nexus1000v.4.2.1.SV2.1.1.zip
Note: VMware typically makes the VEM downloads available via my.vmware.com under the vSphere downloads. However, they are a bit behind so the latest is currently only available on cisco.com
Next, on your Windows laptop, extract/unzip and locate the VEM folder. This is what you will copy up to the host (i.e. enable ssh on the ESXi host, then upload using WinSCP in SCP mode, or alternatively use the datastore browser to upload). It's ok to upload the entire VEM folder if that's easier, or you can just copy over the one file you need:
VEM510-20121019150119-BG-release.zip
My example below assumes the whole VEM folder was copied. Use WinSCP to stage the binary to the /tmp directory on the ESXi host, then issue the following command (adjust path as appropriate for your case) from a console or ssh session on the host (of course this could all be done via vCLI or PowerCLI if so inclined as well. But this is the easy mode install here). The following is an example install, followed by the command used to confirm your VEM and VSM versions:
~ # esxcli software vib install -d /tmp/VEM/VEM510-20121019150119-BG-release.zip
Installation Result
Message: Operation finished successfully.
Reboot Required: false
VIBs Installed: Cisco_bootbank_cisco-vem-v150-esx_4.2.1.2.1.1.0-3.1.2
VIBs Removed:
VIBs Skipped:
~ # vemcmd show version
VEM Version: 4.2.1.2.1.1.0-3.1.2
VSM Version: 4.2(1)SV2(1.1)
System Version: VMware ESXi 5.1.0 Releasebuild-838463
PS - If you don't like the method above, an alternative is using VUM. If configured properly it should install the VEM module automatically upon attempting to join the new host to the vDS / 1000v. You may need to point to the cisco depot to be successful in trying that option.
