Zero Subnetting

[Bill Slaughter]

Is it possible to configure HP-UX 10.2 and/or 11.0 to allow subnet zero? For example, we would like to configure an HP9000 as follows:
IP Address: 150.230.2.4
Subnet mask: 255.255.252.0
Gateway: 150.230.3.254
This would give us a network of 150.230.0.1 through 150.230.3.253.

[John Palmer · Accepted solution]

Bill,

You can stop HP-UX from imposing subnet validation as per RFC 1122 as follows:-

10.20 (needs latest ARPA patch):-
nettune -s ip_check_subnet_addr 0
Needs to be called in a startup script before 'net'.

11.00 ndd -set /dev/ip ip_check_subnet_addr 0
May be added to /etc/rc.config.nddconf but check that this is actioned before 'net'.

Hope this helps.
John

[Bill Slaughter]

Thank you for your correct response. I am glad I got yours first becuase the others were either incorrect or a class on subnet masking that was not responsive to our question.

We found one glitch, the netstat -r command does not seem to understand zero-subnetting, all other functions work fine after following your instructions.

The netstat handg for 15 seconds (or so) and returns bogus network info for the host we are on.