I have a DSL service (Covad) which requires me to set the subnet mask to a subnet having only 5 hosts: gateway : 152.68.6.249 subnet mask: 152.68.6.248 IP's to use: 152.68.6.<250-254> Unfortunately Linux does not let me set the subnet mask to the above value. Solaris and Windows 98 do, and it works fine on those OS's.
Please try a subnet mask of 255.255.255.248 152.68.6.248 is not a valid subnet mask.