https://community.hpe.com/t5/operating-system-hp-ux/subnet-mask/m-p/2509763#M595658 Can someone tell me why in a class C network you cannot have a subnet mask of 255.255.255.128 in HPUX but in Windows98 you can? Tue, 27 Mar 2001 05:25:19 GMT Kelvin Lai 2001-03-27T05:25:19Z https://community.hpe.com/t5/operating-system-hp-ux/subnet-mask/m-p/2509763#M595658 Can someone tell me why in a class C network you cannot have a subnet mask of 255.255.255.128 in HPUX but in Windows98 you can? Tue, 27 Mar 2001 05:25:19 GMT https://community.hpe.com/t5/operating-system-hp-ux/subnet-mask/m-p/2509763#M595658 Kelvin Lai 2001-03-27T05:25:19Z https://community.hpe.com/t5/operating-system-hp-ux/subnet-mask/m-p/2509764#M595659 Hi Kelvin,<BR /><BR />Because HP follow rfc1122.<BR />To bypass RFC-1122 address checking, set the ip_check_subnet_addr variable<BR />to zero. To make this a permanent setting, include this setting in<BR />the /etc/rc.config.d/nddconf file.<BR /><BR />rfc1122 is not allow each network field to be all 1 or all 0.<BR /> Tue, 27 Mar 2001 05:56:22 GMT https://community.hpe.com/t5/operating-system-hp-ux/subnet-mask/m-p/2509764#M595659 Printaporn_1 2001-03-27T05:56:22Z