WRV210 Router - Can't change Static WAN Subnet to 240

[mvcaaadmin]

In the Internet Setup area (WAN) when I change to Static IP I can't change the Subnet Mask from 255.255.255.0 to 255.255.255.240 which is the information currently in my D-Link router.  When I try to save the changes I get the error "The IP address is not in the right subnet".  I find it hard to believe that a lowly D-Link $35 router has nore capability then a Ciso Small Business Router.  Can anyone help?

Thanks

[mvcaaadmin]

Got it!

My static IP was outside the Subnet Mask IP range:

Using the 4th octet address of 240 if I subtract 256 - 240 = 16

so starting at xxx.xx.xx.0

16

32

48

64

80

96

112 and so on....  My IP address was .50 and my Gateway was .45 putting the two IP's outside the .32 to .64 IP address range and in different networks.