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I have two vSphere EXSI 6 servers both setup with the same vSwitchs and connected to the same physical switches

Server 1:

  • eth0 => vlan143 (mapped to CORE/Management vSwitch)
  • eht1 => vlan140 (mapped to SAT vSwitch)
  • eth2 => vlan141 (mapped to ACK vSwitch)

Server 2:

  • eth0 => vlan143 (mapped to CORE/Management vSwitch)
  • eht1 => vlan140 (mapped to SAT vSwitch)
  • eth2 => vlan141 (mapped to ACK vSwitch)

The problem I have is that the Guest VMs on Server 1 cant reach the Guest VMs on Server 2 which are all on the same vSwitches. Both sets of Guests can reach servers that are on vlan143.

The NICs on each host connect to a single physical switch, this switch has the ports setup as access ports.

The two guest are running Windows Server 2008

There is not any VLAN Tagging enabled on the vSwitchs or host interfaces, as when I do connectivity completely breaks down. The Physical switchs do have Vlans.

Appreciate any help or advice offered.

UPDATE 19 April 2016...

OK I think I have found the cause to this, I have noticed that some of the VM's on either ESXI server are not displaying their MAC address's when looking at the vSwitch overview see Screen Grabs Below.

VMServer 1 vSwitch VMServer 2 vSwitch

Now I can reach the VMs from each server that are displaying the MAC addresses, but those that are not showing MACs cant reach the VMs on the other servers. Any help greatly appreciated.

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  • Is each vSwitch connected to a different pNIC on the host? Are the pSwitch ports configured for the correct VLAN's? Do you have inter-VLAN routing configured? Do the virtual machines have appropriate and correct ip addresses?
    – joeqwerty
    Feb 6 '16 at 16:43
  • Yes each vSwitch is connected to a different NIC on the host. The pSwitch ports are configured correctly for the vlans they should be. Intervlan routing is not configured. The VMs do have the correct IPs setup and are both on the correct Subnets.
    – kasonne
    Feb 6 '16 at 17:43
  • It sounds like you're doing EST (External Switch Tagging). So a VM on Host 1 that is connected to a vSwitch that is connected to a pSwitch port that is an access member of VLAN 141 can't communicate to a VM on Host 2 that is connected to a vSwitch that is connected to a pSwitch port that is an access member of VLAN 141? How are the two switches connected? I'm assuming the switch to switch link is configured as a trunk port and that the relevant VLAN's are allowed?
    – joeqwerty
    Feb 6 '16 at 17:50
  • Both Hosts are connected to the same switch (no redundancy in place just yet)
    – kasonne
    Feb 6 '16 at 18:46
  • And to confirm, the hosts are connected to the correct pSwitch ports for the correct VLAN's? Are the pSwitch ports configured as access ports?
    – joeqwerty
    Feb 6 '16 at 18:59
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Hmm, I'd say VLAN tag all the port groups and configure all the pSwitch ports as trunk, then there's no risk of traffic ending up in the wrong due to untagged traffic.

Are all other vSwitches set up like the examples above? Aka. tagged traffic from a port group exiting on a physical port?

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  • Yes all vSwitches are configure the same way.
    – kasonne
    Feb 7 '16 at 22:04
  • Okay, now I get what you're doing there, you're using the core VLAN143 as your management network at the same time, threw me off a bit.
    – Stuggi
    Feb 8 '16 at 5:58
  • What kind of pSwitches are you using? Could you post the configuration for the ports?
    – Stuggi
    Feb 8 '16 at 5:58
  • It should be something along these lines if it's Cisco: ´switchport mode access´ ´switchport access vlan 143´
    – Stuggi
    Feb 8 '16 at 5:59
  • Please See UPDATE
    – kasonne
    Apr 20 '16 at 0:16
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So it turned out that the problem was being caused by the Windows Network Load Balancer, still not 100% sure why, but we disabling NLB everything started working.

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