Thank you, Mr. Phil.
I used Sysinternals ProcMon and NetMon tools and found that there were DNS requests occurring during server boot. but it is not originating from anvil server.
I eventually found the root cause of slowdown — I had installed the VirtualBox/Genymotion emulator, which automatically adds a VirtualBox Ethernet adapter.
That adapter was causing the slowdown. Anvil boots faster after I disabled it.