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Hypercat (Deb)
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VMs on the same host cannot communicate

I have 2 VMs on the same ESXi 5.0 host, on the same vmswitch; they are the only VMs on this host.  They can communicate with the rest of the network with no problem and they can also browse the Internet, but they cannot ping or browse each other. The Windows firewall is turned off on both machines.  I have eliminated any DNS issues (one of the machines is DC and DNS server, and there is another DC/DNS server on the network as well), TCP/IP configuration issues, etc.  File and Printer Sharing is turned on for both servers. One is running Windows 2008R2 Standard, and the other is Windows 2008 Standard. The only conclusion I can reach is that it's something in the ESXi configuration.  Any ideas would be appreciated.
VMwareWindows Server 2008

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Hypercat (Deb)

8/22/2022 - Mon
ajeab

did you check gateway setting?
Hypercat (Deb)

ASKER
Yes, as I said, both machines can browse the Internet, so their gateway settings are correct.
David Johnson, CD

are they in the same subnet and vlan?
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Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)

Have you checked ALL the network settings are the same, Subnet Mask ?

Firewall Disabled on both Hosts?

VMXNET3 interface installed, and VMware Tools ?
Hypercat (Deb)

ASKER
@david - There is only one vlan. All devices at this site are in the same subnet, so if one or both of these machines had the wrong subnet, they wouldn't be able to communicate with anything else on the network.  This is a very simple network, about 65-70 devices total, one network/subnet, one hardware firewall router at the edge.

@andrew - same answer on the network settings.  Windows firewall is disabled by group policy, but I double-checked and it is definitely disabled for all profiles. They are using an E1000 driver for the network interface. I've never had a problem with these, but I could change it if you think it might fix the problem.  VMWare Tools are installed and the service is running.
ASKER CERTIFIED SOLUTION
Andrew Hancock (VMware vExpert PRO / EE Fellow/British Beekeeper)

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Mark Galvin

Have you checked DNS is configured correctly?
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Hypercat (Deb)

ASKER
Changing to the VMXNET3 driver even on just one of the virtual machines fixed the problem. I'm amazed that this made such a difference, especially since when you create a new virtual machine, ESXi defaults to using the E1000 driver for the NIC card. IMO, they ought to change this default if using the older driver can cause this kind of problem on the newer versions of ESXi.  Thanks!