@rochemike
I had the same issue as you did.

To get around this error.
"│ Error: jsonrpc2: code 10 message: invalid parameters: {"errors":[{"instancePath":"/VIFs/0/mac","schemaPath":"#/properties/VIFs/items/properties/mac/minLength","keyword":"minLength","params":{"limit":1},"message":"must NOT have fewer than 1 characters"}]}
│
│ with xenorchestra_vm.rbbmspcs2,
│ on vm-windows.tf line 19, in resource "xenorchestra_vm""rbbmspcs2":
│ 19: resource "xenorchestra_vm""rbbmspcs2" {"

I modified the tf file to pass a mac_address

network { network_id = data.xenorchestra_network.cladevops01net1.id mac_address = be:d0:74:96:5a:66 }

It would then go and create the VM but once created. I'd log into XO, delete the VIF and readd it to get the randomized MAC address.

Please note that I also tried mac_address = null and mac_address = random which also failed.

Hope it helps.

@rochemike sorry for the late reply!

If we already have an ISO on an SR, do we even need to mount the ISO for a network build of Centos/RHEL? Isn't... shouldn't it be possible for the ISO to be mounted by the new build VM as source for creating the new VM, instead of using network build?

That is exactly what packer-plugin-xenserver#56 accomplishes.

The new VM mounts the guest tools to the DVD - which I don't even want to use as I prefer to install a package afterwards. Is it possible to mount the RHEL/Centos ISO instead?

I believe the ISO and guest tools are treated the same -- both VBDs are attached as cds. If you can identify what is different about them in the UI or from the xe cli that would help me understand what you trying to describe.

As for what is possible, if what you want to configure is accessible via the XCP-ng / Xenserver API the packer plugin could be enhanced to perform that action. Hope this helps explain more on the potential possibilities.