After downgrading back to 12.1.671 DA starts working again.
While running 12.1.1000 some strange messages about blocked ETHERNET (type=0x0) and ETHERNET (type=0x2d88) and some other packets could be found from the firewall log, but creating rules to allow those does not help at all. Stopping Symantec services helps and DA works again,.What should be done to get version 12.1.1000 clients to work with DA?