Loopback address with 32 bit netmask

[Jani Kielenniva]

I am trying to assign a 32 bit netmask to a virtual loopback interface in HP-UX B.11.00 U 9000/800 like this:

ifconfig lo0:1 193.120.110.150 netmask 255.255.255.255 up

But it gives the following error:

ifconfig: ioctl (SIOCSIFNETMASK): bad value

ndd -get /dev/ip ip_check_subnet_addr return 0, so this shouldn't affect.

Any ideas how I could get the lo0:1 work with the 32-bit netmask?

[Brian Hackley]

Jani,

You don't need to set the netmask, the host route is created automatically by ifconfig.

netstat -rnv will show:
193.120.110.150/255.255.255.255
193.120.110.150 UH 0 0 lo0:1 4136

ifconfig complains because you are attempting to set what it perceives to be an illegal netmask.

Let us know if there's some reason that this is not working for you.

Regards,

-> Brian Hackley

[John Dvorchak]

Is a 32 bit netmask even valid? Doesn't that leave no room for a host address?

[Joseph T. Wyckoff]

As far as I know, the smallest useful netmask is gonna allow for 4 addresses

ff.ff.ff.fc
or
255.255.255.252

that is a

...00 broadcast (net) address
...01 useful address
...10 useful address
...11 broadcast address

Good Luck