vMotion across datacenters within same vCenter

[KarinB]

Hi All,

I have 1 vCenter server running 6.7 managing 2 separate datacenters, each running hosts with ESXi 6.7. Each datacenter is located in a different physical location and there is no layer 2 connectivity between them.

I need to hot-migrate the VM's from one datacenter to the other and need to make sure I have the proper network configuration to make that happen. We are changing the IP address of the VM's once the VM is migrated to the new location.

My question is:
Do the vMotion networks need to be routable? So if the IP for a host in datacenter 1 is 192.168.2.2 and the IP for a host in datacenter 2 is 10.8.2.3, does the vmknic on the datacenter 1 host need to be able to route to the vmknic on the datacenter 2 host?  Or does it not have to have layer 3 since they are all sitting under the same vCenter server?
*Note that the management networks are already routable, just not the vmotion networks at this time.

Thanks!

[scott28tt]

Moderator: Moved to vSphere Discussions since a broader issue than just ESXi itself.

[ashilkrishnan]

Hi @KarinB ,

vCenter is a management server and does not enable connectivity between all host NICs. It's a configuration on hosts that is required to enable communication between them. As far as vMotion network is concerned, yes you need routing to enable connectivity between vMotion networks in different subnets.

To begin with, you can initiate vmkping from source vMotion vmkernel to target vmkernel --> https://kb.vmware.com/s/article/1003728

Hope that helps

[larstr]

KarinB,

I suspect this is a one time move of the VMs since you're changing ip addresses?

If that's the case I would make one host on each site a temporary special migration host, disabling vmotion on the normal vmkernel nics and enable it on the management interface instead. You've already mentioned that the management interface is routable and then you don't need to setup special routing for vmotion vmkernel interfaces on each host. You would however need to move VMs to this host before changing the vmkernel adapters though.

Good luck!

Lars

[nachogonzalez]

Hey, hope you are doing fine:

If you were to do a cross cluster vMotion please keep in mind the following:

- If vMotion interfaces can not reach each other, vMotion traffic will go trough management interfaces. 
- vMotion interfaces should be routable , please consider using vMotion TCP/IP stack.
- The idea of vMotion is for it to be transparent to the VMs, if you have to change the IP's of VMs something is missing.
What you will need to do is to generate portgroups on the destination cluster with the same vlans / or VXLANs to reflect the origin. 

Let me know if I can assist you with something else.
Warm regards