networking issues esxi replica backup


We hava a couple of esxi hosts that are connected to a vcenter server.

The esxi hosts all have public ip addresses. Now we have added a vkernel with an internal ip adress for each host. This is done so that the vms can be replicated over the internal network and so that the host can be managed over the internal network. The vcenter server has also an ip address in the same internal subnet.

The external ip's are used to backup the vm's to an external location.

So each host has an external and internal ip.

Since we did this change, we get in aprox. 20 % of the vm replica's an error that says "an error occured while communicating with the remote host". This happens randomly, so the vm's with error in one replica job can be successfully replicated the other time. So it's not the same vm's/hosts that generate errors.

Physically, alle the nic are connected to the same switches. There are no vlans yet.

Thanks in advance.
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Brett DanneyIT ArchitectCommented:
How have you set this up at the vSwitch level?
You will need you management\vMotion on one vSwitch, then a VM network on the internal network for the VM's. You would also need an external network for the external IP's. This will ensure that all traffic is being routed correctly.
Peter VVMware InstructorCommented:
You said that "Physically, all the nic are connected to the same switches" but if that is the case then why are you referring to external and internal IP addresses?

Do you have two routers/gateways on the same physical/logical network layer?

If you have 2 network gateways on the same physical/logical layer that will cause issues.
PramoITAuthor Commented:
I think we found it.

At first:
the host and the vcenter al had public ip adresses. let's say:
they were all connected to the same switch which was connected to an uplink.
There was 1 default gateway to the internet.
All went fine

We change all the hosts to privat ip adresses:
We added a nic to the vcenter and gave the vcenter als an ip adress in the range
So no the vcenter had 2 ip adresses, 1 private and 1 public.
We removed all the hosts form vcenter and added them again using the private ip addresses.
Physically nothing change.

All looked fine, but sometimes the vcenter lost the connection to the hosts. In particular during replica backups.

This is what we did today and the problem did not occur anymore.

In vsphere -> administration -> vcenter server settings -> runtime settings -> vcenter server manged IP we put there the private address of the vcenter server.

We removed the public ip address from the vcenter and reconnected all the host. Now it looks like the problem is solved.

I think the hosts or the vcenter stil tried to comunicated over the public ip adresses.

Could this be it?


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Peter VVMware InstructorCommented:
Absolutely, removing the public IP from vCenter is a must. All hosts, and vcenter should have private IPs. Your VMs can have public IPs. I would also make sure there is separate switch for Internal and separate switch for external traffic.
PramoITAuthor Commented:
We found the solution by removing the public ip from vcenter
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