New ESX 6.5 install. DNS lookups to other subnets fail.

[SCampbell1]

Problem: DNS lookups failing from ESX, preventing AD domain join.

Configuration and tests:

• This all works when this same blade is installed with ESX6.0U2
• HPE ESX 6.5 iso
• One NIC with VLAN trunking, and Management VLAN configured with VLAN Id, IP address, subnet and default gateway
• ESXi shell enabled for troubleshooting.
• All inbound connections to the ESX host (web client, classic client, tracert) work from any subnet.
• Output ping from the ESX host to same subnet works
• Output ping from ESX host to DNS server (different subnet) fails from the ESX server, but works from other computers on the same subnet.
• nslookup fails (as expected)
• I'm not real experienced with ESX internals, but ran this with no effect: esxcli firewall set --enable false
• In the LAB on a separate chassis, the ESX 6.5 server can join the domain, but the domain controller is in the same subnet which may or may not be a factor there.

I'm just looking for some troubleshooting or obscure configuration tips for ESX6.5, although a solution would be nice.  🙂

Thanks for any input.

[SCampbell1]

Just an FYI for people reading this thread with similar problems.

After installing the OS in our environment, the host initially comes up with a DHCP-assigned address, and a Powershell script waits for this to happen, then changes the IP address and other information to the correct static IP address.

In ESX 6.0 this causes a restart of the management network.

In ESX 6.5, the behaviour is slightly different, and the management network didn't seem to completely restart.  The problem goes away when the management network is manually restarted from the console.

Next step is to look at how to achieve this through PowerCLI, although since this only happens once at build time, we may just use PowerCLI to reboot the server after these changes are completed.