I'm configuring my new ISP-provided Ubee DVW3201B Home Gateway. In doing this, I'd like to set up my own home network configuration which uses classless subnets. (i.e.: A subnet mask of 255.255.255.0 in 172.16.x.x IP space.) However, I don't see any options in the LAN configuration which allow me to set a custom subnet mask. Is this a feature not available on this device? Does it default to classful subnet masks, or only use a /24 mask?
Sidenote: If anyone's found a manual for this thing, please do share!