Subnetting issues in 10.20

[Trent Cameron]

I am running into trouble trying to assign a subnet mask of 255.255.255.0 to a HP-UX host 24.0.0.254

It will only accpets a subnet mask of 255.0.0.0 Now, I've been around IP for years and I know that 24.0.0.0 is a Class A network, yet 24.0.0.254 subnetted to 255.255.255.0 is a 100% valid IP. (Even though my HP-UX doesn't think so.)

MY QUESTION
-----------
IS THERE A WAY THAT I CAN MODIFY THE RULESET HP-UX 10.20 USES TO VERIFY AN IP ADDRESS OR SUBNET MASK IS VALID??

Thanks in advance for your help.
Trent.

[Vincenzo Restuccia]

Try with SAM.

[Martha Mueller]

We found this to be a problem during our disaster recovery test. However, we were running HP-UX 11.0. The fix was to edit /etc/rc.config.d/nddconf and tell it not to check for class by adding three lines:

TRANSPORT_NAME[0]=ip
NDD_NAME[0]=ip_check_subnet_addr
NDD_VALUE[0]=0

where the number in the square brackets refers to the occurance of the lan card. Use lanscan to get the network information on the card number to use.

[Martha Mueller]

Just ran across your other post - You did specify 10.20. I guess this doesn't apply, after all.

Sorry to waste your time.

[John Bolene · Accepted solution]

Yes, it is a valid subnet now, but it did not used to be valid.

All routers up until a few years ago would not route any addresses that the network or subnetted IP were found to be all 0 or all 1's or ending in 0 or 255.

This was an early IP specification that has been eliminated.

HPUX 10.20 still has this restriction and as has been pointed out, you have to turn off the checking in 11.

So you can't have a network of 24.0.0 and an IP of 0 or 255.

[Wieslaw Krajewski]

Hi Trent,

It could be possible to use subnet zero in 10.20 too, was
slightly more complicated than in 11.00. It required to use adb.
How to do this, have a look into
"Subnet Zero Enable in HPUX 10.20 roobala 04/04/01"
in the Networking forum too.
You'll find there an answer by Printaporn how to do this with the help of adb command.

[Peter Van Sant]

Trent,

The reason you're having problems with this
ip/mask combination is that it is in violation
of rfc1122 which tell us that if you set additional subnetmask bits you MUST use at least one but not of them. Your combination of
24.0.0.254/255.255.255.0 doesn't use any.

To get around this do the following;

1. Install the latest HP-UX 10.x ARPA TRANSPORT CUMULATIVE PATCH.

2. Create a text file called nettune_script in /sbin/init.d with the following line:

/usr/contrib/bin/nettune -s ip_check_subnet_addr 0

3. chmod 555 /sbin/init.d/nettune_script

4. chown bin:bin /sbin/init.d/nettune_script

5. cd /sbin/rc2.d

6. ln -s /sbin/rc2.d/S006subnet

After the next reboot you will be able to set
the mask you want.