The serial number for some Netgear models is not populating in Spectrum. These devices are all modeled as GnSNMPDev. Some have the serial number populated and some do not.
For GnSNMPDev models, Spectrum reads the value of the entPhysicalClass attribute in the Entity mib. If it finds a value of chassis(3), then Spectrum reads the corresponding instance value of the entPhysicalSerialNum attribute and if populated, populates the Serail_Number attribute id 0x10030 with this value.
Some of these devices do not have an entry in the entPhysicalClass attribute where the value is chassis(3).
Release : 10.4.x
Component : Spectrum Discovery and Modeling
This is functioning as designed. Please contact the vendor for any questions concerning the population of the entPhysicalClass attribute in the Entity mib.