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AIX Version 4.3 System Management Guide: Communications and Networks

Installation and Configuration for TCP/IP

For information on installing Transmission Control Protocol/Internet Protocol (TCP/IP), see the AIX Installation Guide.

Configuring TCP/IP

Once the TCP/IP software is installed on your system, you are ready to begin configuring your system.

Many TCP/IP configuration tasks can be performed in more than one way, either by:

For example, the rc.net shell script performs required minimum host configuration for TCP/IP during the system startup process (the rc.net script is run by the configuration manager program during the second boot phase). By using Web-based System Manager or SMIT to perform the host configuration, the rc.net file is configured automatically.

Alternatively, you can configure the rc.net file using a standard editor. With this method, you can specify the traditional UNIX TCP/IP configuration commands such as ifconfig, hostname, and route. (Refer to the "List of TCP/IP Commands" for further information.)

A few tasks, such as configuring a name server, cannot be done using Web-based System Manager or SMIT. (Refer to Fast Paths for TCP/IP in AIX Version 4.3 System Management Guide: Operating System and Devices for a list of tasks in TCP/IP that can be performed using SMIT.)

Configuring Hosts

Each host machine on your network will need to be configured to function according to the needs of the end-users and the network as a whole. For each host on the network, you must configure the network interface, set the Internet address, and set the host name. You also need to set up static routes to gateways or other hosts, specify daemons to be started by default, and set up the /etc/hosts file for name resolution (or set up the host to use a name server for name resolution).

Configuring Hosts as Servers

If the host machine is to have a specific function, for example, if it is to serve as a gateway, file server, or name server, you must perform the necessary configuration tasks after the basic configuration is complete.

For example, if your network is organized hierarchically and you want to use the DOMAIN protocol to resolve names into Internet addresses, you will need to configure at least one name server to provide this function for your network.

Remember, a server host does not have to be a dedicated machine: it can be used for other things as well. For example, if the name server function for your network is fairly small, the machine might also be used as a workstation or as a file server for your network.

Note: If your system has the Network Information Service (NIS) application installed, NIS can also provide name resolution service.

Configuring Gateways

If your network is going to communicate with other networks, you will need to configure at least one gateway host. You will need to consider which communications protocols you will need to support, and then use whichever routing daemon (the routed or gated daemon) supports those protocols.

TCP/IP System Manager Commands

The following list contains the commands you will use to configure and manage your TCP/IP network:

arp Displays or changes the Internet address to hardware address translation tables used by the Address Resolution protocol.
finger Returns information about users on a specified host.
host Shows the Internet address of a specified host or the host name of a specified Internet address.
hostname Shows or sets the Internet name and address of the local host.
ifconfig Configures network interfaces and their characteristics.
netstat Shows local and foreign addresses, routing tables, hardware statistics, and a summary of packets transferred.
no Sets or shows current network kernel options.
ping Determines whether a host is reachable.
route Permits you to manipulate manually the routing tables.
ruptime Shows status information on hosts that are connected to local physical networks and are running the rwhod server.
rwho Shows status information for users on hosts that are connected to local physical networks and running the rwhod server.
setclock Reads the network time service and sets the time and date of the local host accordingly.
timedc Returns information about the timed daemon.
trpt Reports protocol tracing on TCP sockets.
whois Provides the Internet name directory service.

Configuring a TCP/IP Network Checklist

Use the following procedure as a guide for configuring your network, both initially and when you make changes over time. Be certain that you have read and understood the appropriate material. Taking extra time now to understand what you are doing will save you time and frustration later, by avoiding having to correct an earlier mistake.

After you have your network up and running properly, you may find it useful to refer to this checklist for the purpose of debugging the inevitable problems that occur in every network.


  1. Network hardware is installed and cabled (refer to "TCP/IP Network Adapter Cards".
  2. TCP/IP software is installed (see the AIX Installation Guide).


  1. Read "TCP/IP Protocols" and for the basic organization of TCP/IP. You should understand:

  2. Minimally configure each host machine on the network. Specifically, this means adding a network interface, assigning an IP address, and assigning a hostname to each host, as well as defining a default route to your network. First, read "TCP/IP Network Interfaces", "TCP/IP Addressing", and "Choosing Names for Hosts on Your Network". Then, follow the instructions in "Configuring TCP/IP".
    Note: Each machine on the network needs this basic configuration whether it will be an end-user host, a file server, a gateway, or a name server.
  3. Configure and start the inetd daemon on each host machine on the network. Read "TCP/IP Daemons" and then follow the instructions in "Configuring the inetd Daemon".

  4. Configure each host machine either to perform local name resolution or to use a name server. If you are setting up a hierarchical DOMAIN network, configure at least one host to function as a name server. Read and follow the instructions in "TCP/IP Name Resolution".

  5. If your network will communicate with any remote networks, configure at least one host to function as a gateway. The gateway can use static routes or a routing daemon to perform internetwork routing. Read and follow the instructions in "TCP/IP Routing".

  6. Decide which services each host machine on the network will use. By default, all services are available. Follow the instructions in "Client Network Services" if you wish to make a particular service unavailable.

  7. Decide which hosts on the network will be servers, and which service a particular server will provide. Follow the instructions in "Server Network Services" to start the server daemons you wish to run.

  8. Configure any remote print servers you will need. See "Printer Overview" in AIX Version 4.3 Guide to Printers and Printing for more information.

  9. If desired, configure a host to use or serve as master time server for the network. See the timed daemon in the AIX Version 4.3 Commands Reference for more information.

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