what is the exact version of ESXi 6.5 host?
We do find the option available for ESXi 6.5 a version.@
I've seen this before. It depends on your NIC (and the driver for it) wether or not it will give you that option. What type of NIC is it?
VMware ESXi, 6.5.0, 4564106
On 10GbE NICs autonegotiation is not supported.
You are using VMXNET NIC (nested ESXi, 10GbE emulated speed)
Dont worry, its not a bug it should looks like that.
I happened to notice the same issue in ESXi 6.0 update3
I couldn't see the Auto-negotiate option too and have intel x540-at2 network interface on ESXi host.
Putty to the ESXi host and enable auto negotiation on the interface from command line
1. # esxcfg-nics -a <vmnic2>
2. Login into vSphere Client and you should see the autonegotiate appear.
Worked for me with ESXi 6.0 update3