subnetting

[federico_3]

We have a class B network (subnet mask is 2550.255.0.0)and need to apply the subnetting.

How can i set up a subnet like 255.255.128.0 on 10.20 and 11.00.
Can you please specify clearly the procedure because neither with sam nor modifying the network configuration file we can fix the problem


Federico

[Vincent Stedema]

Are you having trouble with configuring your interface with a 255.255.128.0 subnet mask or with adding a route?

[federico_3]

with configuring the interface

[Vincent Stedema]

If SAM says you're using an invalid subnet mask and warns you that you're trying to create a supernet, do the following:

11.00:

# ndd -set /dev/ip ip_check_subnet_addr 0

Add an entry to /etc/rc.config.d/nddconf to disable subnet checking at boot time.

10.20:

# nettune -s ip_check_subnet_addr 0

You'll have to include this line in a boot script (e.g. /sbin/init.d/net) to set this param at boot time.

Hope this helps.

Vincent

[Tim D Fulford]

You can apply a subnet directly to the lan interface. with ifconfig

Take interface down
# ifconfig down
Configure it up
# ifconfig netmask up

eg
# ifconfig lan0 down
# ifconfig lan0 172.19.100.23 netmask \ 255.255.128.0 up

Tim

[federico_3]

Vincent,
ip_check_subnet_addr seems to be not supported ( ndd -h unsup -> shows it)


federico

[Vincent Stedema]

Federico,

What is your current patch level? Some ndd options only work after applying patches (ip_ire_gw_probe, for instance).

Vincent

[federico_3]

Our HP-UX extension Pack is B.11.00.45.

If you try to run :
ndd -h sup
Are there ip_check_subnet_addr and ip_ire_gw_probe ?

Federico

[Vincent Stedema · Accepted solution]

"Supported" has a different meaning in this case. The value of "ip_check_subnet_addr" CAN be changed, but HP doesn't recommend it.

Like the man page says:

"Display all the unsupported tunable parameters.This set of parameters are not supported by HP and modification of these tunable parameters are suggested nor recommended. Setting any unsupported tunable parameters on your system may result in adverse effects to your networking operations."

Hope this helps.

Vincent.

ps. In order to get ndd up-to-date, install the latest ARPA Transport and STREAMS patches.

[Vincent Stedema]

Found a doc (see attach.) that explains it all. Couldn't do it better myself.

Vincent

[John Waller]

Hi,

Your /etc/rc.config.d/netconf file should look something like the following. I personally would manually edit it rather than relying on SAM to get it correct.

INTERFACE_NAME[0]=lan0
IP_ADDRESS[0]=1.2.3.4
SUBNET_MASK[0]=255.255.128.0
BROADCAST_ADDRESS[0]=1.2.127.255
INTERFACE_STATE[0]=""
DHCP_ENABLE[0]=0

or

INTERFACE_NAME[0]=lan0
IP_ADDRESS[0]=100.150.200.4
SUBNET_MASK[0]=255.255.128.0
BROADCAST_ADDRESS[0]=100.150.255.255
INTERFACE_STATE[0]=""
DHCP_ENABLE[0]=0

Notice the difference in the Broadcast address depending on the address of the 3rd IP bit.

Also don't forget that everything on your network will need ammending to reflect the new subnet masks and depending on the IP address they may now need a route entry