UNIX for Dummies Questions & Answers

First ifconfig command:

ifconfig -a
tu1: flags=c63<UP,BROADCAST,NOTRAILERS,RUNNING,MULTICAST,SIMPLEX>
inet 192.168.3.25 netmask ffffff00 broadcast 192.168.3.255 ipmtu 1500

tu0: flags=c63<UP,BROADCAST,NOTRAILERS,RUNNING,MULTICAST,SIMPLEX>
inet 128.1.51.219 netmask ffff0000 broadcast 128.1.255.255 ipmtu 1500

sl0: flags=11<UP,POINTOPOINT>
inet 128.1.19.2 --> 128.1.19.1 netmask ffff0000 ipmtu 296

lo0: flags=100c89<UP,LOOPBACK,NOARP,MULTICAST,SIMPLEX,NOCHECKSUM>
inet 127.0.0.1 netmask ff000000 ipmtu 1536

ppp0: flags=10<POINTOPOINT>


... then network configuration:

***** DISPLAY NETWORK CONFIGURATION *****

Obtaining hardware and software configuration. Please wait...

Current network adapters on this system:

tu1
tu0
sl0

Current software configuration in /etc/rc.config:

HOSTNAME = wsys235
NUM_NETCONFIG = 3
NETDEV_0 = tu0
IFCONFIG_0 = 128.1.51.219 netmask 255.255.0.0
NETDEV_1 = tu1
IFCONFIG_1 = 192.168.3.25 netmask 255.255.0.0
NETDEV_2 = sl0
IFCONFIG_2 = 128.1.19.2 128.1.19.1 netmask 255.255.0.0
SLIPTTY_2 =
RWHOD =
ROUTED =
ROUTED_FLAGS =
GATED =
GATED_FLAGS =
GATED_OLD =
ROUTER =
MAX_NETDEVS = 24


If you compare those two lists you can see that tu1 network adapter configuration is not equal (subnet is diferent). When I try to change subnet throu netsetup unix give me the message:

Enter the subnet mask in dot notation [255.255.0.0]: 255.255.0.0

You provided an incorrect subnet mask. The mask should be of the form
255.255.n.n where each 'n' is a number less than or equal to 255.
The default netmask is 255.255.0.0

If I left default netmask i get same message. I can only left netsetup by pressing Ctrl+c.

Any ideas! Thanx!

I discovered that class C IP automaticly add netmask parameter and can not be changed.

If I use clas B IP space 128.2.X.X then computer sets subnet to 255.255.0.0

Suggestions?!?

Sorry, but I don't understand what you are trying to do.

Do you want to change subnet masks? If so, which ones to what subnet mask?

OK, here is the explanation:

At first we have this computers in network 192.168.1.xxx (home network) with netmask 255.255.255.0

All computers from network 192.168.1.xxx have access to this computer over network (telnet, FTP).


Now we moved this machine to other network (192.168.3.xxx) whitch is connected throu wireles lan and router to home network.


We changed IP addres of the machine from 192.168.1.25 to 192.168.3.25 and netmask from 255.255.255.0 to 255.255.0.0 so computer can be visible from both loactions (both networks).

But then we saw, that even if we changed netmask to 255.255.0.0 network card stil have netmask 255.255.255.0. We checked it with ifconfig :

tu1: flags=c63<UP,BROADCAST,NOTRAILERS,RUNNING,MULTICAST,SIMPLEX>
inet 192.168.3.25 netmask ffffff00 broadcast 192.168.3.255 ipmtu 1500


So we can not change netmask to what we like.

I hope it is clearer now!

Thanks!

I agree with your OS. The subnet mask should be 255.255.255.0. You have two class C networks connected by a router. You need to install routes connecting the two.

Well, I'm new at UNIX so if you have time write me how to instal routes (gateway for 192.168.3.xx is 192.168.3.1).

But the funny thing is that we have two UNIX machines on that location.

One with
Digital UNIX V4.0B (Rev. 564) have problem I described

ifconfig -a
tu1: flags=c63<UP,BROADCAST,NOTRAILERS,RUNNING,MULTICAST,SIMPLEX>
inet 192.168.3.25 netmask ffffff00 broadcast 192.168.3.255 ipmtu 1500

the other one

Digital UNIX V4.0D (Rev. 878) is working just fine with netmask 255.255.0.0

ifconfig -a
tu1: flags=c63<UP,BROADCAST,NOTRAILERS,RUNNING,MULTICAST,SIMPLEX>
inet 192.168.3.46 netmask ffff0000 broadcast 192.168.255.255 ipmtu 1500

I don't know Digital Unix so I don't know which startup script you need to change.

And if the that box with the wrong netmask really can reach systems in your 192.168.1.0 network, and you aren't installing routes on it, then your network topology must be different than what you described anyway.