You'll register vOPs with your vCenter server so it'll need to have a communication link to your vCenter Server host. Page 9 lists the ports for that - www.vmware.com/pdf/vcops-5-installation-guide.pdf.
You'll also access the client either directly with a web browser, or via the vSphere client plugin, but either method is access the UI VM on https. Whatever VLAN you use to access vCenter would be fine for the vApp.