You need to assign VLANs(Port group) for ESX hosts. VSwitch should do VLAN tagging for you. You just configure trunk ports on network side.
So, it is liable that it sends untagged packets (you would otherwise have encountered some related settings some day or another...).
Perhaps could you then define the vlan you want to boot in as the native vlan on the trunk?
i need to pxe boot on the vmnic0. but I also need to have this on a trunk port so that i can tagg it in vsphere with vlan ids.
right now I cannot pxe boot off this vmnic0 because its on native vlan 1. the pxe/dhcp server is on vlan 60.