I'm running an SMS pilot in a large corporation with many VLANS.  I have enabled SMS Discovery, defined the VLAN in the Site Boundaries, and added the subnet into the Network Discovery settings, but SMS is not retrieving any discovered clients.

I'm able to setup the client directly on the workstation from a logon script or manually.  I have verified that the SMS VLAN is open for all IP traffic from all my boundaries VLAN.  What ports are used by SMS for discovery and what am I doing wrong?

Contributed By: Wally Mead [MS]
Most likely the issue is that we can't discover the client's subnet mask, which we do require in order to create a discovery record for the resource.

We only discover subnet masks through router ARP caches, Microsoft DHCP, or a local SNMP agent on the client.  If none of these are available, then we won't have the subnet mask, and won't report the resource.