I ran a test in my lab using Spectrum 10.2.1 installed on Linux.
I created a custom $SPECROOT/custom/Event/EventDisp entry to generate a Critical alarm
I create a custom $SPECROOT/custom/Event/AlertMap file to send a trap and save the value of a varbind to event variable 16.
I added the event id only to the $SPECROOT/SS/CsVendor/Ctron_Gen_HOST/Host_Device/EventDisp file.
I modeled a Host_Device model
I set the Enable_SouthboundGateway attribute id 0x116296e to Yes on the Host_Device model
I used TrapGen to send a trap to the ip address of the Host_Device model where the value of the varbind was the model name of a different model in the Spectrum database.
No alarm was asserted on the Host_Device model
The critical alarm was asserted on the target model as expected
Joe