I use ISA server which manages and hosts its own WPAD, so if you use the ISA WPAD, you are somewhat limited if you share a DNS namespace. True, you could enable netmask ordering, or you can abandon the built-in WPAD and write and host your own that is subnet aware. You can also opt to host WPAD through DHCP option 252 and not worry about the namespace.
Since I am DivIT and share the DNS namespace with other divisions and CorpIT, I opted for DHCP 252. I cannot speak for other divisions nor for CorpIT but suspect that they don't use WPAD. Their loss.
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Give a man a fish and he will be back for more. Slap him with a fish and he will go away forever.
