VM unable to ping another VM in different ESX host with the same VM Network Label

Hi All,

I'm having weird issue here with one of my VM, the SCCM Vm in the below scenario cannot even ping the domain controller (DC02-VM) hosted in different ESXi blade host while it can ping the DC01-VM in the same blade host.

in the vSwitch there are two pNIC working as the uplink simultaneously. All of the servers only have one vNIC.

ESXi01 contains the following VM:
SCCM01-VM
DC01-VM

ESXi02 contains the following VM:
DC02-VM

after migrating it into another host as follows, the SCCM server can ping to the DC02-VM which wasn't ping-able, but now it cannot ping DC01-VM:
ESXi01 contains the following VM:
DC01-VM

ESXi02 contains the following VM:
DC02-VM
SCCM01-VM

the strange thing is that between DC01-VM and DC02-VM they can both ping-ing to each other.

what to look for and idea for trouble shoot please ?
I noticed that the VM network label are all the same VLAN and IP address class.
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Senior IT System EngineerIT ProfessionalAsked:
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HarsemConnect With a Mentor Commented:
One thing I forgot about

The physical switch that these two ESX Servers are conencted to. Is it just 1 switch or are there 2 (or more) switches involved in traffic from ESXi01 to ESXi02?

If they are seperate you also have to ensure that the VLAN that these VMs communicate over is also allowed to pass the link that connects these switches.
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
are the VLANs tagged correctly on the vSphere vSwitch and physical switch.
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HarsemConnect With a Mentor Commented:
Hello,

From what you have described I would suggest that the physical switch to which the ESX hosts are connected to are not properly configured.

Most likely the VLAN that is hosting these VMs is not tagged to one or both of the ports that the ESX Servers are connected to.

ESX uses its own internal Virtual Switch (vSwitch) to which the VMs connect. In turn you connect that vSwitch to a physical NIC which then leads to the physical switch.

Seeing that things work within ESX, it look slike the physical switch that is defeating you here.

Jens
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Senior IT System EngineerIT ProfessionalAuthor Commented:
Hm.. if that is the case then it is the Networking team issue not us the server team ?
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
could you upload screenshots of your vSwitches

what physical switches are you using.
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HarsemConnect With a Mentor Commented:
Hello,

from what you have written that is where I would check next.

it might well be that the VLAN Tag is not being sent through to your ESX Server(s). It may be sent to one, but not the other, but that is impossible to tell from what you have described.

If you are using Cisco switches & Cisco Discovery Protocal is enabled, then you can press on the Blue icon next to the NIC in Configuration->Networking
 CDPThis shows you to which Switch port your ESX Server is connected. This can be used to verify if the networking team has configured the correct Switch Port.

If this is not a production environment you can try to create a new Virtual Machine network - but this time do not assign a VLAN ID - do this on both ESX Servers and move your VMs into it. If they can ping each other (across the ESX Servers) then it is almost certain that a VLAN as not been properly presented to the ESX NIC on which that VLAN should be active.

Jens
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Senior IT System EngineerIT ProfessionalAuthor Commented:
I believe that there are two CISCO switches for redundancy reason.

the Cisco CDP is turned off based on PCI requirement (for security purpose in production facility).
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HarsemConnect With a Mentor Commented:
If they are there for redundancy then is it correc tthat each single switch is connected to both ESXi01 & 02 Server.

In which case I would check VLAN Tags on the ESX ports of the Cisco Switch.
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Andrew Hancock (VMware vExpert / EE MVE^2)Connect With a Mentor VMware and Virtualization ConsultantCommented:
Ask you network engineers for the Cisco configuration of the switches and compare between switches and server ports.
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Andrew Hancock (VMware vExpert / EE MVE^2)VMware and Virtualization ConsultantCommented:
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HarsemCommented:
Hello,

did you have an update for us?
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Senior IT System EngineerIT ProfessionalAuthor Commented:
Yes it is the network config changes.
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