Configuring PPP on SCO UNIX OpenServer 5.0.X
PPP (which stands for Point-to-Point Protocol) is a necessary tool for connecting remotely located PCs into your local area network through the modem. Once the PPP link is established, the remote PC will be able to access the UNIX host just as if the PC were locally connected. The UNIX host can even be configured to act as a router/gateway between the remote PC and the local PCs allowing these PCs to talk to each other.
This document covers the installation and configuration of the PPP drivers on a SCO UNIX OpenServer 5.0.0 through SCO UNIX OpenServer 5.0.5. It covers the setup of only dynamic incoming connections. Any additional information about PPP can be obtained from SCO web site, www.sco.com, under the documentation area. FacetCorp makes no claims about the accuracy of this document and we are not responsible for any errors that it may contain. The configuring of the Dial-up networking on Windows is covered in the FacetWin manual under Configuring a FacetWin Dial-up Connection or in the FacetWin help files under the same heading.
The installation and configuration for SCO UNIX 3.2v4.2 (also known as OpenServer 3 or ODT 3) is not covered in this document. This subject is covered in a separate document.
Installing the PPP drivers
Before installing the PPP drivers, make sure the following items are completed or met first:
This minimum patch list for all base levels of SCO UNIX can be found on the SCO website at the following URL:
http://www.sco.com/support/toolbox/patch.html
These patches are critical because they address known TCP/IP issues.
You need to make sure that you can establish a simple dial-in connection to your UNIX host through a modem. If you get any kind of screen garbage or screen corruption, contact your UNIX support to get this resolved before going on.
This is critical. For a dial-up PPP connection to work best, you need to make sure that you have hardware flow control established between the modem and UNIX serial port. If you are not sure if it is setup or if this needs to be done, contact your UNIX support for help with this.
This is done by issuing the "ifconfig –a" command. This command will list all of the currently installed network interfaces. The interface we are listed in will be the one that is labeled net0 or net1. The output of the ifconfig command looks like this:
net0: flags=4043<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.52.1 netmask ffffff00 broadcast 192.168.52.255
perf. params: recv size: 4096; send size: 8192; full-size frames: 1
ether 00:20:af:e4:ab:5c
The first line after the net0 line tells us the IP address (inet) and the netmask for the UNIX host. The netmask is given in hexadecimal notation. Here is a simple translation table:
ffffff00 = 255.255.255.0
ffff0000 = 255.255.0.0
ff000000 = 255.0.0.0
Now that the preliminaries are setup, let’s install the PPP drivers into the UNIX system. This is done through the netconfig utility. The first menu that comes up should list all of the current networking drivers and interfaces currently installed on the UNIX system. If you already have a reference to "SW SCO TCP/IP PPP driver" listed, then you can skip this section and go directly to the "Configuring additional PPP links" section.
Go to the Hardware menu bar option and select "Add new WAN connection". This should bring up an option to select either the PPP or the SLIP (Serial Line Internet Protocol). Make sure you select PPP. This should then give you a list of transport layer protocols currently installed on your system. Select the "SCO TCP/IP". This will take you another menu giving you the choice of what PPP connection type you wish. Select the "Dynamic Incoming" option. This will take you to the "PPP Dynamic Incoming Link Configuration" screen.
Creating the first PPP link
This section covers the initial configuration of a PPP link during the PPP driver installation. Before we get started, we need to cover a few items related to IP addressing and PPP links.
1. Restricted numbers
Do not use the numbers 0, 127 or 255 anywhere in the PPP link IP addresses. These are reserved as special numbers in the IP layer itself.
2. Determining new network addresses
Setting up the PPP link is essentially setting up separate network interfaces on your UNIX host. This requires setting up different network addresses for each link you will be configuring. First, determine what your current UNIX network address is. This is based in part on the netmask configured and the actual IP address of the server. Usually, the netmask is set to 255.255.255.0. This means that the first 3 numbers in your UNIX host’s IP address make up the network address. For example, your UNIX host has an IP address of 192.168.52.1. Your network address would be 192.168.52. To create a different network address for the PPP link would just entail adding 1 to the last number in the network address. In the previous example, a PPP link address could now be 192.168.53. For each additional PPP link you wish to configure, just continue adding 1 to the last number in the network address remembering to avoid the restricted number.
If your network addressing does not follow in the simple example above, you should contact FacetWin technical support. The support contact information is listed below.
3. Link IP address pairs
The network address determined above now needs to be used to create pairs of IP addresses for use by the UNIX host and the remote PC. Continuing with the example above, you could use 192.168.53.1 for the UNIX host and 192.168.53.2 as the address for the remote PC for your first PPP link. If you created a second link, you could use 192.168.54.1 and 192.168.54.2 for the UNIX host/remote PC pair. Again, these addresses must be created in pairs.
Let’s pickup from the installation process where the "PPP Dynamic Incoming Link Configuration" screen is being displayed. This screen covers the main addressing information. Here are the fields you will need to fill in:
PPP login name
This is automatically filled in with the name of "nppp" for the first PPP link you setup. You can fill this in with any new UNIX account name you wish. Using "ppp" somewhere in the account name will make administration easier in the future. You will be able to readily identify your PPP users.
Local host name
This field can actually be left empty. If the field has a name in it, SCO will attempt to add this information along with the "Host IP address" information into the /etc/hosts file for you.
Host IP address
This is the full IP address you will be assigning to the UNIX side of the PPP link. This is the host side of the IP address pair you created above.
Destination name
This field like the "Local host name" is an optional field. If you wish to fill it in, this field should contain the name of the remote PC the user will be logging in from.
Destination IP address
This is the remote side of the IP address pair you created above.
Netmask
This should be set to the same value as your physical network netmask. On most systems, this is a value of 255.255.255.0.
There is an "Advanced Options …" selection. Go ahead and select this option. A new screen with lots of information to be possibly filled in comes up. There are only two entries that are important to us. The first one is the Debug level: entry. Make sure that this is set to 0. If you run into problems, this can be set up to a higher level for diagnostic purposes. The second entry is the Line flow control: entry. Set this to rtscts. This is the proper setting for hardware flow control as we talked about earlier.
Now that all of the fields have been filled in, select the OK menu option to save all of these settings. You will be asked some information regarding the setup of the nppp account at this point. The first question asks if you want to specify user id for the nppp account?. Answer n. This will assign the next available user ID to the nppp account. The second question will be to set a password for the nppp account. Assign a password for this account as you would normally for any other UNIX account. Finally, you will be asked to configure more links. Go ahead and select the "No" option. This should return you to the main netconfig menu.
Final notes on initial PPP setup
Once back at the main netconfig menu, go ahead and exit the netconfig utility. You will be prompted to re-link the kernel. You must do the re-link and a reboot of the UNIX system before you can use the PPP connection you just created. Be sure to answer yes to any of the questions asked during the kernel re-link process.
If you will be testing on a PC that has a regular network connection to the UNIX host, you will need to temporarily change the IP address of the network card on the PC. Change the address to something that is in no way related to the network address of the UNIX system. This is necessary because Windows will still attempt to connect to the UNIX host through the network card even when dialed directly into the UNIX host.
Modifying and configuring additional PPP links
The way we have set this up in-house is to setup a separate PPP link account for each user that will be logging into the system. To add another link, run netconfig. Select the "SW SCO TCP/IP PPP driver" in the main window. Go back up to the menu bar, go under the Hardware option and "Modify hardware configuration". This will bring up a list of currently configured PPP links. Just select the "< > Add" option towards the bottom to add another link. This will bring up the first screen as described in the "Creating the first PPP link" section above. Just follow the same steps listed in that section.
You can also highlight any one of the existing links and modify those link characteristics. Say you need to change the IP address pair. Just highlight PPP link you wish to configure and press the space bar to activate it. This will bring up the first screen that lists all of the IP address information about that link.
Manually configuring and modifying PPP links
All of the link information you entered during the setup is actually stored in the /etc/ppphosts file. You can manually edit this file to make any changes you wish. There are lots of notes describing all of the options and fields you can enter in this file. One note: if you make any changes to this file, you need to signal the pppd process that there have been changes. You do this by issuing a "kill –1" command on the PID listed in the /etc/pppd.pid file. The pppd process will not actually shutdown. The "kill –1" tells the pppd process to re-read the /etc/ppphosts file and use the modified parameters.
Final notes
Sometimes things don’t quite go as planned or you might have a situation not exactly covered by this document. If you do, please feel free to contact the technical support department. Here is the various contact information for the support department:
Support Hours: 8:30 AM to 5:00 PM Central
Support Telephone: (972) 985-9901
Support Fax: (972) 612-2035
Support E-mail: support@facetcorp.com