There are 3 main types of Signature Updates.

1) IPS Sensor Signature Updates

2) CSM Signature Updates for IPS Sensors

3) IOS IPS Signature Updates

The IPS Signature Update filename is in the form: IPS-sig-Sxxx-req-Ey.pkg

This is most likely what you are referrnig to in your post. This file can be installed on ANY IDS/IPS Appliance or Module.

The Requirement here is not the platform but rather the Engine Level. The "req-Ey" portion of the filename tells you that the sensor must already be running the "y" Engine level of software.

So an IPS-sig-S436-req-E3.pkg file can be installed on any IDS/IPS Appliance or Module so long as the software on that sensor is an "E3" version.

The CSM updates, are signature updates for the Cisco Security Manager. They contain special files that CSM uses to update itself, and then also included within the CSM update is the actual sensor update described above. CSM unpackages the CSM update, updates itself, and then uses that embedded file to upgrade the actual sensor.

The third type of file is for IOS Routers loaded with special IOS software that has the special IOS IPS features where the Router itself (instead of a separate IDS/IPS module) does the signature monitoring.

These IOS IPS Signature Updates get installed on the actual router, and are not installed on the IDS/IPS Sensor Appliances or Modules.

So in answer to your question, yes the same Signature Update for your IDSM-2 is the exact same Signature Update for your SSM modules.

The exact same file is available through multiple different paths on cisco.com. But it doesn't matter through which cisco.com path you downloaded the file you can still install it on all IDS/IPS Appliances and Modules.

As for licensing, the license works the same on all IDS/IPS Appliances and Modules. A license must be on the sensor for the Signature Update to be applied.

NOTE: A Trial License is available from cisco.com for new sensors to allow you time to get everything setup correctly for your sensor to be covered by a service contract, and get the standard license from the service contract.