We’re recently changed our network design to have two core switches setup with VRRP and multicasting.
We have a few legacy Windows 2003 machines which since the change have started acting a little odd. Theysuddenly stop seeing anything outside of their Vlan but can ping/talk to anything within their vlan.
Hopping on to the box as local admin and clearing ARP and pinging out allows them to resume talking to other devices outside of their native VLan for a few hours and then it starts again.
I’m convinced it is to do with enabling multicasting within the network and have added within the registry on the server for IMGPLevel (2) and IGMPVersion (4) under TCPIP Parameters.