How to Easily Configure TCP/IP on Your AIX System

Contents

About this document

This document describes how to configure TCP/IP on your AIX system. With AIX, you can configure your TCP/IP network with a single command, mktcpip. On other systems, setting up TCP/IP might involve creating and editing multiple files, executing a number of commands, setting various variables, locating values for persistence after reboot, and starting several daemons. The mktcpip command completes all the necessary TCP/IP configuration tasks for a typical system. The process is even easier when you use the System Management Interface Tool (SMIT) to prompt you for all necessary parameters to configure your network.

After you gather the prerequisite information, you can run the mktcpip command three ways: by using SMIT, the command line, or the Web-based System Manager.

Related documentation

AIX and related product documentation is also available:
http://www.rs6000.ibm.com/resource/aix_resource/Pubs/index.html

Prerequisites

Gather your network configuration information:

• IP address
• Host name
• Domain Name
• Subnetmask (optional)
• Name server (optional)
• Gateway address (optional)

Procedure

Configuring TCP/IP is easiest when you use SMIT. On the command line, enter the following fast path:

        smitty mktcpip

A dialog box requests which type of interface you plan to use. Then, SMIT builds a screen that lists each required value. After you fill in the fields with the network information that you have collected, the tool runs the mktcpip command in the background and makes the network available. Your task is finished.

If you prefer the command line approach, you can specify all the necessary parameters in a single instruction, as shown in the following example:

        mktcpip -h server1 -a 10.47.1.3 -m 255.255.0.0 -i en0 \
        -n 9.3.240.2 -d itsc.austin.ibm.com -g 9.3.240.1 -s -C 0 -A no

If you prefer a more graphical interface, you can use the Web-based System Manager tool to complete this task. This tool uses icons, windows, and wizards to guide you through the configuration. To start this interface, enter the following on the command line:

        wsm

No matter which method you choose, online help is available to assist you. For example, to access online help within SMIT, use the F1 key.

If you want to further configure your network, for example, if you want to select more than one interface type, SMIT has an easy interface for that, too. On the command line, enter:

smitty configtcp

Further configuration

Customizing your TCP/IP configuration beyond the minimal configuration is easily done through SMIT, the command line, or the Web-based System Manager. SMIT menus guide you through such tasks as:

• Managing static routes
• Flushing the routing table
• Setting or showing host names
• Managing network interfaces or drivers
• Managing domain names or the hosts table (/etc/hosts file)
• Managing network services for the client or server
• Starting or stopping TCP/IP daemons

Naming conventions for your network devices and interfaces

When you install AIX, it automatically detects each adapter card and installs the corresponding interface software. AIX uses the following naming convention for network devices and interfaces:

Device Type                                                            Device Name                Interface Name

Asynchronous Transfer Mode (ATM)                         atm#                               at#

Ethernet (IEEE 802.3)                                                ent#                                et#

Ethernet (Standard, Version 2)                                    ent#                                en#

Fiber Distributed Data Interface (FDDI)                     fddi#                                fi#

Loopback                                                                  N/A                                 lo#

Token-ring                                                                 tok#                                 tr#

• The # sign represents the number of the device or interface you intend to use.

Gateways

A machine can communicate to the network through a gateway. A gateway contains the addressing and routing information for each host on its network, and can use routing daemons to broadcast routing information to, and receive routing information from, other gateways. TCP/IP routes information to the appropriate computer on the network using address information carried in a packet or stream of information.

AIX version 5.0 allows a host to discover if one of its gateways is down (called dead gateway detection) and, if so, choose a backup gateway, if one has been configured. Dead gateway detection can be passive (the default) or active.

• In passive mode, a host looks for an alternate gateway when normal TCP or ARP requests notice the gateway is not responding. Passive mode provides a "best effort" service and requires very little overhead, but there may be a lag of several minutes before a dead gateway is noticed.
• In active mode, the host periodically pings the gateways. If a gateway fails to respond to several consecutive pings, the host chooses an alternate gateway. Active mode incurs added overhead, but maintains high availability for your network.

In either mode, the host chooses the alternate gateway with the lowest associated cost value. You determine the cost value, using any criteria you wish, when configuring TCP/IP. The value can be any number from 0 (the default) to 2147482647.

Flags for the mktcpip command

The mktcpip command can do much more than minimal TCP/IP configuration. The following table defines all the flags available for the mktcpip command.

-A yes/no

Active dead gateway detection (AIX Version 5.0 and later), if set to no (the default), dead gateway detection remains in passive mode.

-a Address

Sets the Internet address of the host. Specify the address in dotted decimal notation. Each network interface on the host should have a unique Internet address. The following is the standard format for setting the Internet address:

127.10.31.2

-C number

Specifies the cost of using the selected interface type. This value affects which alternate gateway is chosen when dead gateway detection (AIX Version 5.0 and later) determines the current gateway is down. The value can be any number from 0 (the default) to 2147482647.

-c Subchannel

Specifies the subchannel address for a System/370 channel adapter.

-D Destination

Sets the destination address for a static route. Specify the address in dotted decimal notation. The following is the standard format for setting the destination address for a static route:

192.9.52.1

-d Domain

Specifies the domain name of the name server the host should use for name resolution, if any. The domain name should be in the following format:

subdomain.subdomain.rootdomain

-g Gateway

Sets the gateway address for a static route. Specify the address in dotted decimal notation. The following is the standard format for setting the gateway address for a static route:

192.9.52.0

-h Hostname

Sets the name of the host. If using a domain naming system, the domain and any subdomains must be specified. The following is the standard format for setting the host name:

hostname

The following is the standard format for setting the host name in a domain naming system:

hostname.subdomain.subdomain.rootdomain

-i Interface

Specifies a particular network interface, for example:

tr0

-m SubnetMask

Specifies the mask that the gateway should use in determining the appropriate subnetwork for routing. The subnet mask is a set of 4 bytes, as in the Internet address. The subnet mask consists of high bits (1s) corresponding to the bit positions of the network and subnetwork address, and low bits (0s) corresponding to the bit positions of the host address.

-n NameserverAddress

Specifies the Internet address of the name server that the host uses for name resolution, if applicable. The address should be entered in dotted decimal notation, for example:

127.1.0.1

-r RingSpeed

Specifies the ring speed for a token-ring adapter. Valid values for the RingSpeed variable are either 4- or 16-Mbps.

-S Interface

Retrieves information for System Management Interface Tool (SMIT) display.

-s

Starts the TCP/IP daemons.

-t CableType

Specifies cable size for Standard Ethernet or IEEE 802.3 Ethernet networks. Valid values for the CableType variable are dix for thick cable, bnc for thin cable, or N/A for Not Applicable. The -t CableType flag should be used only for Standard Ethernet (en) and IEEE 802.3 Ethernet (et) interfaces.

TCP/IP subsystems

The mktcpip command runs a shell script called rc.tcpip to start the TCP/IP daemons for your configuration. The script contains start stanzas for the following daemons:

autoconf6, ndpd-host

Internet Protocol version 6 (IPv6)

dhcpcd, dhcprd, dhrcpsd

Dynamic Host Control Protocol (DHCP) daemons

inetd

Internet daemon that starts related services such as telnet and ftp

lpd

Print server daemon

mrouted

Multicast routing daemon

named

Domain name server in a domain network

portmap

Port lookup facility used for remote procedure calls (RPCs)

routed or gated

Dynamic routing (both daemons cannot run simultaneously)

rwhod

Remote uptime and users daemon

sendmail

Mail transfer agent

snmpd, dpid2

Simple network management protocol (SNMP) daemons

syslog

Log server for standard UNIX error logs

timed, xntpd

Time synchronization daemons

By default, the script starts the syslogd, portmap, inetd, lpd, and sendmail daemons and puts their entries into the /etc/inittab file so the subsystems begin automatically after every reboot. To automatically start any of the other listed daemons, simply uncomment their corresponding lines in the rc.tcpip file. You can add start stanzas for other daemons, too.

Useful TCP/IP references

Configuration, status, and troubleshooting commands