How to prevent domain controllers from attempting authentication on 2nd NIC

I have setup a second NIC on my domain controllers and assigned a new VLAN for a backup-only network for DPM.  This works but I've found that the 2nd NICs are broadcasting as available domain authentication points.  This is causing problems for our wireless access points that are not VLAN aware.  How can I prevent the 2nd NICs from offering authentication services over the network?

Thanks,
Joe