The configuration of the local TCP/IP protocol stack is specified in a file that is read each time you start TCP/IP, including at the time of system boot. The NetcomRouter installation uses this standard file to identify the configuration of the devices used to deliver IP traffic over X.25 lines.
This section documents the entries in the TCP/IP configuration file, allowing you to modify them, and implement a change to your local IP configuration without reinstalling the product. It also describes how to map a remote IP address to a remote X.25 address. This section does not describe the tunable parameters which affect IP Routing and other items not commonly changed. See Tuning NetcomRouter for those details.
Note that the IP addresses in this file may appear as a name (found in /etc/hosts) or as a numeric address. Both are equivalent.
Important Note for SCO Users
If you are using an SCO ODT, SCO OpenServer 5, or SCO 3.4.2 UNIX
system, the easiest method for reconfiguring interfaces or adding new
interfaces is to use the netconfig utility. See SCO's
Netconfig Utility.
The installation script creates one or more WAN/IP devices which are referred to as the xinet interface . Each device named xinetN corresponds to one of eight possible IP network addresses. References to these devices are found in the TCP/IP configuration files.
Often in TCP/IP networks, a local IP address and IP network are assigned to each physical interface. This is done with an ifconfig command. However, with NetcomRouter devices, the IP address and the file /etc/x25hosts determines the board and link number used to send the data to that host, separate from the interface used. That is, each device represents a logical interfaces -- it is not directly associated with any physical connection. It is therefore possible to have several IP addresses (that is, several ifconfig statements) associated with one physical X.25 link. Likewise, it it possible to have one ifconfig statement that sets one IP address for several X.25 physical links.
root uses the startup file to start or stop TCP/IP, as does the operating system when it starts up or changes state. When you add or delete X.25/IP interfaces (change whether or not a device is to be used), you must change this file.
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If you are using |
The format of the ifconfig line is |
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SCO ODT and 3.4.2 UNIX |
ifconfig xinetN local_ip_address up network mask your_network mask |
ifconfig mpfN local_ip_address up network mask your_network mask |
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SCO OpenServer 5 |
ifconfig -p xinetN local_ip_address up network mask your_network mask |
ifconfig -p mpfN local_ip_address up network mask your_network mask |
In both cases, N is the number of the next device that you are using. Place these lines with the rest of the ifconfig commands in the /etc/tcp file.
Each interface must have a separate IP address which is on a separate IP network or subnet. It is important to understand the concept of an IP network, which is described in Network Design.
The previous section describes the file that configures the TCP/IP protocol stack. This section outlines the file that describes how the protocol stack is to be built. The file describes, for example, that TCP should be linked above IP. And that IP should linked above some Ethernet device and an xinet device. If all you want to do is change the configuration of the stack, the previous section is all you need. If you want to add or delete xinet devices, then you will need to follow this section.
Specifically, /etc/strcf is a file that describes how the protocol stack is built. NetcomRouter uses function x25net in this file to link the xinet device under the IP driver.
For SCO systems, you can add an entry to /etc/strcf if you wish to add new IP devices (to have new IP networks on X.25). Use the following lines:
ip = open /dev/inet/ip
x25net ip /dev/xinet_ xinet N
You need the first line only if it does not already exist. You need one x25net command for each local IP address associated with X.25 lines. Replace N with the device number you are using.
For those familiar with TCP/IP traffic in a LAN environment, there is a hidden protocol sending information between the systems. Address Resolution Protocol (ARP) maps IP addresses to MAC addresses (for example, Ethernet or Token Ring addresses).
ARP uses broadcasts that send information about the local IP address and the associated local MAC address to everyone on the LAN. Each machine builds a table of IP to MAC address mappings, thereby learning how to contact each IP address. This works well in a LAN environment. However, the necessary broadcast packets that ARP uses do not work well in a WAN environment. You simply cannot broadcast information about your configuration to every system in the X.25 network.
Instead, the installer has to manually build a table that describes the association between each remote IP address and the X.25 address where it can be found. Remote host and X.25 address pairs are stored in /etc/x25hosts. Hosts in this file that are designated to support IP traffic (that is, a host with the IP flag) are added to the addressing mapping table. If, in the future, you wish to add or change entries in the I P address mapping table, you may edit /etc/x25hosts directly. The x25route utility reads this file and passes it to the driver. Whenever you make changes to this file, you will need to rerun x25route.
An entry in x25hosts would look something like this:
12345678 remoteIPhost link00 IP
Here, the IP address remoteIPhost is associated with netid named link00 and a remote X.25 address 12345678. The netid determines the physical wire to be use as described in
Note: The default maximum number of remote X.25 hosts is 20. If your network requires more than 20 entries in /etc/x25hosts, the variable NXINETADDRMAP in the file /etc/conf/pack.d/xinet0/space.c must be changed. See Tuning NetcomRouter
On SCO Unix systems, the install script sets up files that allow you to add, delete, or reconfigure NetcomRouter devices.
When you run netconfig, you are presented with a menu similar to the following:
Currently configured chains:
1. tcp_x25- > xinet0
tcp_x25 SCO TCP/IP for UNIX for X.25
xinet0 X.25 Router, device 0
2. sco_tcp- > lo0
sco_tcp SCO TCP/IP for UNIX
lo0 SCO TCP/IP Loopback driver
3. sco_tcp- > e3B0
sco_tcp SCO TCP/IP for UNIX
e3B0 3Com 503 Ethernet driver, board 0
Available options:
1. Add a chain
2. Remove a chain
3. Reconfigure an element in a chain
q. Quit
Select option:
The module tcp_x25 is similar to sco_tcp used for Ethernet interfaces, except that it does not link to the ARP module.
From this menu you can add a chain (add an xinetn device) or reconfigure an existing one. As in the original product installation, you will be asked for the IP address and network mask You can also delete existing xinetN devices from the TCP/IP configuration. In all cases, you will be required to reboot the system for the new configuration to take effect.
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