This document describes basic setup and configuration tips for the DHCP server in conjunction with TCP/IP.
This information applies to AIX Version 4.x.
This document was written and tested with the preceding operating systems. Though the techniques and information contained in this item may work on other levels of the operating system, they have not necessarily been tested. Normal precautions should be taken in adopting these same techniques and procedures in your own environment.
The AIX product documentation contains a detailed description of the DHCP server, client and relay agent processes and their respective configuration file formats. Other related information is also found in the online product documentation using the TCP/IP and DNS search paths.
As a means to distribute to clients IP addresses and parameters such as hostnames, netmasks, and DNS information, DHCP also works well as a tool for updating DNS zones and with information relevant to the network clients.
DHCP is a mechanism for the automatic network configuration of hosts through IP while IP addresses become "real estate" controlled by the server and are issued (leased) to each client.
There are numerous configurations and network topologies to consider when configuring a DHCP server. The server configuration file /etc/dhcpsd.cnf contains entries for logging information, options to return, machines to configure, and other items.
File: /etc/dhcpsd.cnf
NOTE: This information does not contain the usual documentation found inside the /etc/dhcpsd.cnf file.
Please change option 15 to your domain name.
EXAMPLE #1
NOTE: This is a basic configuration for AIX operating system levels up to and including 4.2.1. This configuration is portable on AIX 4.3.1 platforms, but requires file set enhancements other than the 4.3.1 operation system base level installation. See CASE #7, Configuring DHCP at AIX Version 4.3.1.
network 144.21.0.0 144.21.13.191-144.21.13.222
{
option 1 255.255.255.0
option 3 144.21.13.11
option 6 144.21.13.31
option 15 austin.ibm.com
}
numLogFiles 4
logFileSize 100
logFileName /usr/tmp/dhcpsd.log
logItem SYSERR
logItem OBJERR
logItem PROTERR
logItem WARNING
logItem EVENT
logItem ACTION
logItem INFO
logItem ACNTING
logItem TRACE
leaseTimeDefault 30 minute
leaseExpireInterval 3 minute
supportBOOTP Yes
supportUnlistedClients Yes
The following two lines of code should appear on one line.
updateDNS "/usr/sbin/dhcpaction '%s' '%s' '%s' '%s' BOTH NONIM >> /tmp/updns.out 2>&1 "EXAMPLE #2
NOTE: This is a basic configuration for AIX operating system levels up to and including 4.2.1. This configuration is portable on AIX 4.3.1 platforms, but requires file set enhancements other than the 4.3.1 operation system base level installation. See CASE #7, Configuring DHCP at AIX version 4.3.1.
network 144.21.0.0 24
{
subnet 144.21.16.0 144.21.16.191-144.21.16.222
{
option 1 255.255.255.0
option 3 144.21.16.11
option 6 144.21.13.31
option 15 austin.ibm.com
}
}
numLogFiles 4
logFileSize 100
logFileName /usr/tmp/dhcpsd.log
logItem SYSERR
logItem OBJERR
logItem PROTERR
logItem WARNING
logItem EVENT
logItem ACTION
logItem INFO
logItem ACNTING
logItem TRACE
leaseTimeDefault 30 minute
leaseExpireInterval 3 minute
supportBOOTP Yes
supportUnlistedClients Yes
The following two lines of code should appear on one line.
updateDNS "/usr/sbin/dhcpaction '%s' '%s' '%s' '%s' BOTH NONIM >> /tmp/updns.out 2>&1 "
File: /etc/dhcpsd.cnf
NOTES:
This is a basic configuration for AIX operating system levels up to and including 4.2.1. This configuration is portable on AIX 4.3.1 platforms, but requires file set enhancements other than the 4.3.1 operation system base level installation. See CASE #7, Configuring DHCP at AIX version 4.3.1.
This information does not contain the usual documentation found inside the /etc/dhcpsd.cnf file.
Please change option 15 to your domain name.
network 171.28.0.0 24
{
option 1 255.255.255.0
option 6 144.21.13.31
option 15 subdomain.austin.ibm.com
subnet 171.28.4.0 171.28.4.220-171.28.4.250
{
option 3 171.28.4.10
}
subnet 171.28.7.0 171.28.7.220-171.28.7.250
{
option 3 171.28.7.10
}
subnet 171.28.16.0 171.28.16.220-171.28.16.250
{
option 3 171.28.16.10
}
subnet 171.28.17.0 171.28.17.220-171.28.17.250
{
option 3 171.28.17.10
}
}
numLogFiles 4 logFileSize 100 logFileName /usr/tmp/dhcpsd.log logItem SYSERR logItem OBJERR logItem PROTERR logItem WARNING logItem EVENT logItem ACTION logItem INFO logItem ACNTING logItem TRACE leaseTimeDefault 30 minute leaseExpireInterval 3 minute supportBOOTP Yes supportUnlistedClients Yes
The following two lines of code should appear on one line.
updateDNS "/usr/sbin/dhcpaction '%s' '%s' '%s' '%s' BOTH NONIM >> /tmp/updns.out 2>&1 "
File: /etc/dhcpsd.cnf
NOTE: This information does not contain the usual documentation found inside the /etc/dhcpsd.cnf file.
NOTE: Please change option 15 to your domain name.
The Client assignment line shows how to give this client the same ipaddress every time. Only this client can receive this ipaddress.
The Client exclusion line shows how to deny or exclude this ipaddress. No client can receive this ipaddress. The server status will show Not Available for this ipaddress.
network 144.21.0.0 24
{
subnet 144.21.16.0 144.21.16.195-144.21.16.220
{
client 1 0x00aa00c12c2d 144.21.16.199 # Client assignment
client 0 0 144.21.16.200 # Client exclusion
option 1 255.255.255.0
option 3 144.21.16.11
option 6 144.21.13.31
option 15 austin.ibm.com
}
}
numLogFiles 4 logFileSize 100 logFileName /usr/tmp/dhcpsd.log logItem SYSERR logItem OBJERR logItem PROTERR logItem WARNING logItem EVENT logItem ACTION logItem INFO logItem ACNTING logItem TRACE leaseTimeDefault 30 minute leaseExpireInterval 3 minute supportBOOTP Yes supportUnlistedClients Yes
The following two lines of code should appear on one line.
updateDNS "/usr/sbin/dhcpaction '%s' '%s' '%s' '%s' BOTH NONIM >> /tmp/updns.out 2>&1 "
File: /etc/dhcpsd.cnf
NOTE: Please change option 15 to your domain name.
network 144.21.0.0 144.21.13.191-144.21.13.222
{
option 1 255.255.255.0
option 3 144.21.13.11
option 6 144.21.13.31
option 15 austin.ibm.com
}
network 144.21.0.0 24
{
subnet 144.21.16.0 144.21.16.195-144.21.16.220
{
option 1 255.255.255.0
option 3 144.21.16.11
option 6 144.21.13.31
option 15 austin.ibm.com
}
}
network 171.28.0.0 24
{
option 1 255.255.255.0
option 6 144.21.13.31
option 15 austin.ibm.com
subnet 171.28.4.0 171.28.4.220-171.28.4.250
{
option 3 171.28.4.10
}
subnet 171.28.7.0 171.28.7.220-171.28.7.250
{
option 3 171.28.7.10
}
subnet 171.28.16.0 171.28.16.220-171.28.16.250
{
option 3 171.28.16.10
}
subnet 171.28.17.0 171.28.17.220-171.28.17.250
{
option 3 171.28.17.10
}
}
#Log file and trace information. See other examples in other cases.
The following two lines of code should appear on one line.
updateDNS "/usr/sbin/dhcpaction '%s' '%s' '%s' '%s' BOTH NONIM >> /tmp/updns.out 2>&1 "
File: /etc/dhcpsd.cnf
NOTE: This information does not contain the usual documentation found inside the /etc/dhcpsd.cnf file.
supportBOOTP Yes supportUnlistedClients Yes
These lines are not mutually exclusive. They should both be yes to support bootp clients. /usr/sbin/bootptodhcp is a converter routine for bootp client support.
The following steps should be taken to support bootp clients:
See IX58812 for a problem with a backslash "\" in /etc/bootptab.
File: /etc/dhcpsd.cnf
NOTE: This information does not contain the usual documentation found inside the /etc/dhcpsd.cnf file.
The following two lines of code should appear on one line.
updateDNS "/usr/sbin/dhcpaction '%s' '%s' '%s' '%s' BOTH NONIM >>
This line must be uncommented in the /etc/dhcpsd.cnf file. The nameserver must support DDNS. At the time of this writing, AIX 4.1.4 and AIX 4.2.0 are the only operating systems that support DDNS. No other vendor's OS supports DDNS with the exception of WindowsNT beta v4. This beta or test version of WindowsNT may support DDNS.
Please perform the following steps for DHCP and DDNS.
In the /etc/dhcpsd.cnf file:
updateDNS "/usr/sbin/dhcpaction '%s' '%s' '%s' '%s' PTR NONIM >>
The PTR means the pointer record will be updated. This is the default value. If you want to update the A record and the pointer record, you should change the PTR to BOTH.
That line will read (the following two lines of code should appear on one line):
updateDNS "/usr/sbin/dhcpaction '%s' '%s' '%s' '%s' BOTH NONIM >>
primary domainname.com /etc/named.data dynamic controlled primary in-addr.arpa /etc/named.rev dynamic controlled
The dynamic keyword is required for the named.rev line if the updateDNS line shows the PTR update. Since the updateDNS line shows BOTH NONIM then the dynamic keyword is required for the named.data and named.rev lines in the /etc/named.boot file.
Add the keyword controlled to the dynamic lines, as it acts like secured and allows updates.
Refresh the named subsystem: refresh -s named
DDNS is documented in the online product documentation using the following search path:
'List of Books'
'AIX System Management Guide: Communications and Networks'
'TCP/IP Name Resolution'
EXAMPLE /etc/named.boot file:
primary ztrans.com /etc/named.data dynamic controlled primary 0.0.127.in-addr.arpa /etc/named.local primary 32.3.9.in-addr.arpa /etc/named.rev cache . /etc/named.ca
Configuring the DHCP server is usually the most difficult part of using DHCP in your network. First, determine what networks you need to have DHCP clients on. Each subnet in your network represents a pool of addresses that the DHCP server must add to its database. For example:
database db_file {
subnet 9.3.149.0 255.255.255.0
{ option 3 9.3.149.1 # The default gateway clients on this network should
use
option 6 9.3.149.2 # The nameserver for clients on this network should
use
}
... options or other containers
added later
}
The preceding example shows a subnet, 9.3.149.0, with a subnet mask 255.255.255.0.
All addresses in this subnet, 9.3.149.1 through 9.3.149.254, are in the pool.
Optionally, a range can be specified on the end of the line or a range or
exclude statement can be included in the subnet container. See DHCP Server File
Known Options for common configuration methods and definitions.
The database clause with db_file indicates which database method to use for processing this part of the configuration file. Comments begin with a # (pound sign). Text from the # to the end of the line is ignored by the DHCP server. Each option line is used by the server to tell the client what to do. DHCP Server File Known Options describes the currently supported and known options. See DHCP Server File Syntax for General Server Operation for ways to specify options that the server does not know about.
If the server does not understand how to parse an option, it uses default methods to send the option to the client. This also allows the DHCP server to send site-specific options that are not RFC defined, but may be used by certain clients or client configurations.
EXAMPLE #1
logging_info
{
numLogFiles 5
logFileSize 500
logFileName /bcp/TEMP/dhcpsd.log
logItem SYSERR
logItem OBJERR
logItem PROTERR
logItem ACNTING
logItem ACTION
logItem EVENT
}
database db_file
{
leaseExpireInterval 4 hour
leaseTimeDefault 8 days
supportBOOTP No
supportUnlistedClients Yes
subnet 10.0.0.0 255.0.0.0 subnet1A:1
{
range 10.20.128.2-10.20.128.128
client 6 002035018496 10.20.128.128
option 1 255.0.0.0
option 3 10.10.10.1
option 6 10.10.10.5
option 6 10.10.10.3
option 15 burbank.aic.com
option 44 10.10.10.104
option 44 10.10.10.105
option 46 08
}
subnet 192.10.10.0 255.255.255.0 192.10.10.11-192.10.10.11 subnet1B:1
{
exclude 192.10.10.11 # Remvove the only initial range address
}
virtual fill subnet1A subnet1B
}
------------------------------------------------------------
INFO: getPortNum: dhcps/udp unknown service, assuming port 67
SYSERR: createMailbox: bind socket failed - The socket name is
already in use.
SYSERR: main: cannot create transport facility. Exit dhcpsd.
log: END
-------------------------------------------------------------
When the above error is received, it is common for the dhcpsd process to die. This error is common when bootp is running under inetd. bootpd and dhcpsd cannot run at the same time. The dhcpsd process uses the same service port as bootps; however, dhcpsd is not an inetd subserver and is started in the /etc/rc.tcpip file, not /etc/inetd.conf. The bootps line in /etc/inetd.conf must be commented out with #. inetd must be refreshed using the command:
refresh -s inetd .The bootps line in /etc/services remains as is:
bootps 67/udp # bootp server port
------------------------------------------------------------ TRACE: am_queryClient: client 1-0x00aa00c12c2d is not known to address mapper, ask clientele TRACE: cl_queryClientele: client 1-0x00aa00c12c2d rejected in clientele list OBJERR: am_queryClient: clientele failed when queried about client 1-0x00aa00c12c2d INFO: processDISCOVER: client 1-0x00aa00c12c2d authentication failed ACTION: reply_generator: no reply is generated TRACE: main: No reply is to be generated -------------------------------------------------------------
This error was generated when the DHCP server configuration file shows the following two lines:
supportBOOTP Yes supportUnlistedClients No
This error was corrected by changing the line: supportUnlistedClients Yes
------------------------------------------------------------ 09/05/96 09:39:38 SYSERR: ....initUserComm: bind usercomm socket failed - The socket name is not available on this system. 09/05/96 09:39:38 SYSERR: ..main: cannot create user communications socket. Exit -------------------------------------------------------------
The above error occurs when the value for hostid is incorrect. There may be an incorrect entry in /etc/hosts and so on. The hostid must be a valid address for at least one of the networks defined in /etc/dhcpsd.cnf. The hostid command returns, in hex, the value of the system's ipaddress. The hex value 0x8123cae3 can be converted to decimal and be equal to 129.35.202.227. This is a valid ipaddress for a DHCP server.
The SMIT interface on AIX ONLY applies to the DHCP client configuration. The DHCP server configuration uses a motif interface run by the command /usr/sbin/dhcpsconf. However, the preceding server configuration examples can be modified into your own environment using vi or any editing tool which may be quicker and more effective than running the DHCP server motif interface.
The SMIT fastpath smit tcpip brings you to a screen where you can select DHCP as follows: Use DHCP for TCPIP Configuration & Startup. After selecting the interface, the Client configuration is set in this screen. Execution of this screen will pass the hostname of this client to the DHCP server for DDNS updates and start the dhcpcd (client daemon) process. The /etc/rc.net file and /etc/rc.tcpip file both are modified to run DHCP as a client. The variable modified in the /etc/rc.net file is USE_DHCP="1". The line which starts /usr/sbin/dhcpcd is uncommented in the /etc/rc.tcpip file.
SIDE EFFECTS
If the DHCP Client service is started using the SMIT interface, but the system administrator or user never intended for this system to be a DHCP Client or run DHCP services, you will find unusual behavior and a corrupt configuration after a system reboot.
Two symptoms of this are that the hostname is changed to loopback or localhost and the default route no longer exists.
You can run ps -ef | grep dhcpcd and see if the client process is running. netstat -rn will verify the routing table.
There are two ways to stop the Client service: