Migrate vms from vss to vds

Hi dear,
I have two questions, can you help me, please?
1. when vm's migrate from vss to vds switch, really what changes happen in host and vCenter?
2. Do exist way that when a VM migrate from vss to vds, don't happen loss network ?
Very thanks from your helps,
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Hamid SaeedAsked:
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
1. nothing changes in the host or vCenter Server, but the VMs networking must change from the vss virtual machine portgroup to the vds virutal machine portgroup. So it's a VM change. Assuming that VDS is already configured on hosts via vCenter Server.

2. providing vss and vds networking is correct and complete, the change over can be done in real time, by switching over networking, but there will be a moment of network loss, depends on how heavily loaded the VM is, at the time of switch over.

We would always recommend completing out of core hours, to avoid outages.
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Hamid SaeedAuthor Commented:
Hi dear,
Thanks for your helps,
Ok,
Excuse me, when vds use what happen for vss?

Thanks,
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Nothing, it's not used, and can be removed.

vss uses different physical uplinks to vds.
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Hamid SaeedAuthor Commented:
Hi dear,
Ok,
So,as a result:
In a vss:
A VM has a mac address, and it connect to a uplink, and uplink connected to physical switch, and vss has mac:port forwarding table,

In vds :
We add host and their physical nics to vds,and vm networking too,

1. Is it right that again vm use from same physical nic that before, it  use on vss for send it's traffic?

I want know what changes  occur that after migrating in vds, that physical switch must be update through notify switches feature?

Thanks dears,
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
traffic goes through the new vSwitch, and different port if required
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Hamid SaeedAuthor Commented:
Very thanks,
I read in vss :
ESXi will send out an RARP , When a virtual machine is powered-on,means,
When vSwitch assigns a physical NIC to a vNIC, ESXi will need to send a RARP frame to enable the switch to update its lookup table with a new physical port number mapping for the vNICs MAC address. This is necessary because every time a virtual machine is powered-on it is not guaranteed the same vNIC to PNIC mapping.

1. Even if a VM with a pNIC exist , it send arp, after vm power off and power on?

2.Do it in  vds is right ? Even if  vm use from same pnic , it send arp?

In generally, if a VM running migrate to vds and after migrating vm use from same pNIC, in here not change pNIC , so not need send arp to physical switch?


Thanks,
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
if you are migrating from VSS to VDS you will have no issues.

As for ESXi definition - yes.

You make a change to networking, and it will send the RARP.
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Hamid SaeedAuthor Commented:
Hi,
You say :
You make a change to networking, and it will send the RARP.

Means,  if vm port in virtual switch changed,even if uplink not change, it send rarp again?
Really what things must change that it send rarp?
Thanks,
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Correct.

Networking of the VM, so the physical switch, knows which port the MAC Address is on!

ESXi does send RARPs at various other times, e.g. when VMs are vMotioned to maintain forwarding tables in your physical switches.

and it's the HOST ESXi server which sends the RARP on behalf of the VM.

So the physical switch understands the MAC:PORT (physical switch) relationship. - this is why the RARP is sent, so if you move a VM from one vSwitch to another vSwitch, which is on different physical ports, RARP will...
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Hamid SaeedAuthor Commented:
As result,
I say , when I have a port group with a uplink that have a pNIC , why with change virtual switch port for a VM , it send rarp?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
ESXi decides to send RARP on behalf of the VM, to notify the physical switch of any changes.
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Hamid SaeedAuthor Commented:
Thanks, dear
My problem is solved if I understand that what things send to physical switch for when :

I have a port group with a uplink that have a pNIC ,so

why when vm off and on , and while it still use same pNIC , after  off and on vm  what things notify to  physical switch?

Means, what info it send to physical switch for that  notify it?

While pNIC not changed and from before   switch know that a VM with given mac address is connected with same pnic,

Now what info it send to physical switch for that  notify it?

Thanks,
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
When you set the switch to notify, ESX will give permissions, to send fake RARP frames on behalf of the VMs.

this is so, he physical switches, can be updated quickly.

This is helpful, if you are using more than one nic per vSwitch e.g. teaming, and the MAC Addresses need to be moved to the other network interface uplink quickly, if an uplink should fail.

So in Summary RARPS are used for

1. Power on and Power OFF, RARP is sent.

2. vMotion RARP is sent.

3. Teaming Failure, and Notify switch set to Yes.

when the NOTIFY option is set to Yes.

If set to No, ESXi will not send RARPS, and you could experience packet loss, before physical switches learn where MAC Addresses are located on which ports. But VMs should still work and function.
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Hamid SaeedAuthor Commented:
Ok dear,
So, when  esx send many  rarp for a VM in when change pnics in team ,
What is behavior of physical switch with repeated rarps?

My question is, when secend rarp for a VM is send to physical switch,
1.  what is behavior physical switch with  old entires in it's mac table?
2. Another state is : when vm off and on while nothings change, in time esx send a rarp that is same with later RARP ,
Now switch how behair with rarp that duplicate later?

Very thanks,
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Ok dear,
So, when  esx send many  rarp for a VM in when change pnics in team ,
What is behavior of physical switch with repeated rarps?

updates physical switch tables.

My question is, when secend rarp for a VM is send to physical switch,
1.  what is behavior physical switch with  old entires in it's mac table?
2. Another state is : when vm off and on while nothings change, in time esx send a rarp that is same with later RARP ,
Now switch how behair with rarp that duplicate later?

replaces the existing entry, updates the tables.

You can observe this if you use Wireshark, to packet sniff your network.
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Hamid SaeedAuthor Commented:
Very thanks,
I understand that main goal  notify switches is tell  to physical switch what vm is on, is right ? Or has it another goal?

So, now when a VM power off , how physical switch be notify it for update it's table?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
Very thanks,
I understand that main goal  notify switches is tell  to physical switch what vm is on, is right ? Or has it another goal?

we covered that here in this post...

https://www.experts-exchange.com/questions/29012251/Migrate-vms-from-vss-to-vds.html#a42073151

So, now when a VM power off , how physical switch be notify it for update it's table?

the MAC address:Port, in the physical switch will be the same value, when the VM was on. If the VM is off, the VM is off.
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Hamid SaeedAuthor Commented:
Ok dear,
Very very thanks for your helps,
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