I've had this issue before, but can't remember how I resolved it. Basically, we are switching out some network gear so I'm recreating the vLans into a more organized layout since they are kind of all over. As I back out the old vlans, some of them don't want to leave the reporting of NPM and are listed as down or unknown. I've tried forcing a resources update, repolling, double checking my configs to ensure the vlan isn't hanging around in my core still being reported. Anyone else have an issue like this ? Any suggestions would be a great help.