In a previous article in this series, Building Your Network, Part 1, we examined how to configure workstations on a LAN, and promised that we would deal with the Gateway in a future article. That time has now come. First, however, we should briefly define a few basic terms.

Terminology

1. LAN/WAN

   The LAN (local area network) or WAN (wide area network) is a closed system. Communication within the LAN (or WAN) is often handled by NETBIOS because of its greater power. By closed, I mean it is controlled entirely by the Network Administrator and normally there is no access to computers outside the LAN. ¹ In particular workstations on a LAN have no access to the world at large.

2. Gateway

   The Gateway is the name given to the workstation on a LAN that is also connected to the Internet. (A Gateway computer is also commonly called a router, but technically "Gateway" is the more accurate, and less confusing, term.) ² The Gateway computer also contains the firewall and filtering software. The Gateway, then, serves two vital functions: it provides workstations on the LAN with access to the Internet and thereby the world at large, AND if properly configured it protects the workstations from illegal accesses by hackers and other unauthorized software and/or personnel.

3. Firewall

   Here's the definition of "Firewall" according to the InJoy Firewall Reference Manual:

   In fact, a firewall is a conceptual object rather than a specific software or hardware product. It is the concept of rejecting all traffic except that which is specifically allowed. It should allow the administrator of the firewall to control all traffic into and out of a network.

   In other words the firewall is the armed guard at the Gateway to the LAN.

   Firewall Components

   1. Rule Based Access Control

      Here a set of Rules defined by the Network Administrator is recorded in a file. Every time a connection is attempted (incoming or outgoing), the firewall software checks the Rules file to see if the connection is allowed. If it is not, the firewall closes the connection.

   2. Network Address Translation (NAT)

      Simply stated, the firewall uses NAT to hide the internal workstation addresses, and to re-address all outgoing messages from workstations on the LAN by replacing internal IP addresses with the external IP address of the Gateway.

   3. Packet Filtering

      Packet Filtering operates closest to the hardware, and allows individual packets to be selectively discarded based on predetermined criteria. In InJoy Firewall, Packet Filtering operates on raw packets.

   The Injoy Firewall package used for the purposes of this series contains other specialized security protocols relating to tunneling and virtual private networks that I will not discuss here.

4. Router

   As used here, router is simply the device (hardware and/or software) that performs the switching between networks, in particular, as in our case, between a LAN and the Internet. (See the Lucent Communication Glossary for more information.)

5. Hostname

   Hostname is the alphanumeric (e.g. os2.about.com) name of the server to which a computer is connected by means of an Internet dial-up, ethernet LAN connection, ISDN connection, etc.

6. IP Address

   The numeric address (e.g. 206.41.16.82) that identifies a computer on the Internet.

7. Nameserver

   A server containing a database of IP addresses and their alphanumeric equivalents and lookup software that remote computers can use to convert the latter into the former.

TCP/IP Notebook

The next major step to is configure the TCP/IP Configuration notebook, located in the System Setup folder, which in turn is located in the OS/2 System folder.

1. The interface number corresponds with the slot number of the adapter card (NIC). From my experience it appears that the Internet "automagically" grabs interface 0 when you are installing the drivers and corresponding network software.

2. The LAN interface 0 IP Address and Subnet Address are examples only. You must use the data you are given by your Internet Provider.

3. This is the Gateway, and is configured with two LAN cards.³ Therefore it must have two LAN interface pages configured, one for each LAN card.

4. The second interface is on the LAN side of the Gateway and is configured exactly like a workstation with a Class B local address, in this case, 192.168.1.1. Note: This address must be the same as the address specified as the Router in each of the other Workstations on your LAN. (See the Building Your Network, Part 1 in this series.)

Next page > Routing  > Page 1, 2

—Walter Metcalf

Next week: Installing and setting up the Firewall