For OM12 RTM the Excel sheet OperationsManager2012_ExtendedMonitoringForNetworkDevices.xlsx shows 834 network devices in total which are supported for extended network monitoring.
When SP1 for OM12 became GA it wasn’t very clear whether extended network monitoring was still the same or additional devices were added. For some weeks a new Excel sheet is available for OM12 SP1 extended network monitoring, SystemCenter2012_SP1_OperationsManager_ExtendedMonitoringForNetworkDevices.xlsx.
This Excel sheet shows an additional 302 network devices supported for extended network monitoring. So OM12 SP1 supports 834 + 302 = 1136 network devices for extended network monitoring.
Both Excel sheets can be downloaded from here.
And as Microsoft states on the same webpage: ‘…For a complete list of devices covered with System Center 2012 Service Pack 1 (SP1), Operations Manager, you will need to download BOTH documents…’