A past student of mine, Mike K. posed a great question to me today. " I had a request today to add a DHCP scope option #156 which has a string of ftp server= I went to the scope options dialog box and only saw this go as high as 121! Where / how can I set this?
      GREAT question Mike! After some digging the answer had revealed itself. He was right this is NOT a place you can just randomly add a custom scope option. This can only be done at the server level. Now this is where it varies slightly from WS2k3 to 2k8. In Server 2003, you can right click the server object in the DHCP MMC and select "Set Pre-defined options" or on 2k8 server, right click on IPv4 and choose the same. From here on it’s identicall (nearly)
      So from here he was able to click on the Add.. button and add it as the new code and proper value type of string.