Configure TCP/IP on Your AIX System

Configure TCP/IP on Your AIX System

Summary: 

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 

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

smitty mktcpip

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, type the following on the command line:

Wsm

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, type:

smitty configtcp

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.

Name Services

If you use name services, you can provide the minimal information needed through the mktcpip command. Typically, the /etc/resolv.conf file stores your domain name and name server IP address. The mktcpip command creates or updates the /etc/resolv.conf file for you. By default, the resolver routines on hosts running TCP/IP use the following lookup sequence:

1. Domain Name Server (DNS)

2. Network Information Service (NIS or NIS+), if active

3. Local /etc/hosts file

But you can override the default lookup by editing the /etc/netsvc.conf file. Also, you can set the NSORDER environment variable to override the host settings in the /etc/netsvc.conf file.

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.

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.

Configuration, Status, and Troubleshooting Commands
lsdev -Cc adapter and	List system adapters and IP interfaces
lsdev -Cc if
netstat -in	Show status of IP interfaces with numeric addresses
netstat -rn	Show status of TCP/IP routes with numeric addresses
arp -a	Display local ARP cache
no -a and no -o	Display/set kernel variable values, such as ipforwarding
ifconfig and route	Display status and configure temporarily
mkdev (chdev, rmdev, etc.) and SMIT	Configure permanently
lsattr -El	Display ODM database attributes for the specified interface or adapter
nslookup	Troubleshoot DNS
host	Resolve host name to IP address and vice versa
hostname	Display current local host name
System Files
/etc/hosts	Local hosts table
/etc/rc.*	Scripts for TCP/IP, NFS, and so forth
/etc/resolv.conf	Name resolver
/etc/netsvc.conf	Name resolution order
/usr/sample/tcpip/named.*	Sample files that can be copied and edited
/etc/named.*	DNS resolution files
/etc/hosts.equiv,	Remote user access files
/etc/rhosts, and /etc/hosts.lpd