Techniques for detecting device changes using SNMP polling are described. In response to determining that an MIB of a managed device has changed, the device's SNMP agent identifies the altered objects in the device's MIB. In response to detecting such a change, the SNMP agent generates a bitmap. This bitmap identifies all the MIB's objects that have changed. The NMS may access and use this bitmap to take further action. For example, the NMS may use the bitmap to poll only the changed objects in the MIB, rather than all of the objects in the MIB (including the unchanged objects). Because fewer than all of the MIB's objects need to be polled in order to identify changes to the managed device, both the burden on the device and the bandwidth required for the polling is significantly reduced.