In Bitcoin QT 0.12 for Windows, how do you whitelist an IP address? I believe the answer is that you enter the command line option whitebind for IPV4 or whitelist for IPV6.

When I tried it, I first got a message that I needed to include the port, so I included the port, but then I got an error message saying "Unable to bind to {IP.Add.re.ss:Port} on this computer (bind returned the error The requested address is not valid in its context. (10049))."

I did a search for whitelisting multiple IP addresses and didn't find any results, but through experimentation, I determined that repeating the command line option multiple times works, at least to get the errors I describe above.
There are 4 options (either command line or in the bitcoind.conf file) that have to do with whitelisting. I myself have only used whitelist where you simply specify the IP address (IPv4), without port number.

-whitelist=192.168.10.20

According to the documentation you can also specify a netmask, which I haven't used yet, but should be in this format if I'm not mistaken:

-whitelist=192.168.10.0/24


  -whitebind=
         Bind to given address and whitelist peers connecting to it. Use
         [host]:port notation for IPv6
  
  -whitelist=
         Whitelist peers connecting from the given netmask or IP address. Can be
         specified multiple times. Whitelisted peers cannot be DoS banned and
         their transactions are always relayed, even if they are already in the
         mempool, useful e.g. for a gateway
  
  -whitelistrelay
         Accept relayed transactions received from whitelisted peers even when
         not relaying transactions (default: 1)
  
  -whitelistforcerelay
         Force relay of transactions from whitelisted peers even they violate
         local relay policy (default: 1)