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Once you have decided that using DHCP will provide a benefit,
you will need to follow the steps below to set up a DHCP server. Note
that only one DHCP server per network subnet is required.
On the server system: Allocate a set of currently unused
IP addresses (preferably a contiguous block of addresses). For example: 15.1.48.50 -> 15.1.48.80 Pre-assign and register hostnames to the IP address
allocated above. Using the -h option to the dhcptools command may be useful.
For example, this command creates a /tmp/dhcphosts file that can be incorporated into your /etc/hosts or DNS/NIS database: dhcptools -h fip=15.1.48.50 no=30 sm=255.255.255.0 hn=devlab## Designate a system to act as the DHCP server for
your network. This should be a system that is "always" available
to it's clients.
Use SAM to configure the DHCP services on this server: As root, enter: sam (you may need to set your DISPLAY variable to use the graphical version) Double-click Networking and Communications Double-click Bootable Devices Double-click DHCP Device Groups Booting From this Server You should now see a screen that lists any DHCP groups already
defined (there may not be any if DHCP is not already configured). To add the new group of IP addresses which you allocated
in Step 1, click Action -> Add DHCP Group Now fill in the information on this screen. Some information
may require additional research if you are not familiar with the
terms or with your network. Group Name — This
can be any name that isn't already defined as a DHCP group. For
example: group1 Subnet Address — This
is the portion of an IP address that is not masked off by the subnet
mask (see below). If you don't want to figure this out, then just
enter one of the IP addresses in the range you picked along with
the correct subnet mask and SAM will take care of the calculation.
For example: 15.1.48.50 Subnet Mask — This
depends on the "class" of your network, and basically determines
how an IP address is separated into a network number and a host
specific number. Press F1 in this field for more information. For example: 255.255.255.0 Subnet Address Pool — Press
this button to select the range of IP addresses that you allocated
in Step 1. A new screen will display where you can enter the Start
and End address. If there are addresses within the range that you
picked that you do not want allocated via DHCP, you can use the
Reserved Addresses button to specify those (or ranges of them). Allow Any Device Class — The
SAM default allows any type of DHCP device to use the group of IP
address you are configuring. This may be undesirable if you use
a different method (or a different DHCP server or group) for managing
systems such as PCs running Windows98™ or NT™. If you want this range of addresses to be used only by HP-UX systems,
then unselect this button, and in the text field provided enter: HewlettPackard.HP-UX When using Ignite-UX to set up DHCP, it will set a class specific
to the server, and will set the dhcp_class_id string to match. For more detail, see the instl_adm manpage. Automatic Allocation to Bootp Clients — Leave
this option disabled. Enabling it will cause problems for bootp
devices such as printers and terminals which rely only on their
preconfigured server to respond to their boot request. Accept New Clients — Leave
this option enabled. Address Lease Time — The
lease time should be set sufficiently long so that if a client system
is temporarily out of service (off) for a time, its lease will not expire too soon. Infinite leases will never expire and disable the IP-address reclamation
features of DHCP. For example: 2 weeks. Boot file name — You
can leave this field blank. Additional Params — There
are many parameters that can be specified in this screen for such
things as the default routers, time server, DNS server, and NIS
domain. You can specify as much or as little as you like in this
area. Callback Routines — None
are necessary.
Once the parameters are all filled in, then press OK on the Add DHCP Group screen. SAM will then make the modifications
to the /etc/dhcptab file. Click Action -> Enable Boot Server (if it is not already enabled).
New systems that are installed with HP-UX 10.20 or newer version
or booted with a pre-installed HP-UX 10.20 or newer version should
now contact this server to get an IP address lease and other network information
provided by the server. Details
of the DHCP Services | |
When cold-installing HP-UX 10.20 or
newer: The installation tools will broadcast out on the network for
any available DHCP servers. The first server to respond will be
chosen to provide the default network information that the user
is presented with. In the network parameters screen during a cold install, you
see the question: "Is this networking information only temporary?" Responding yes or no answer to this question implies the following: no (the default) means that if the IP address and
hostname were leased from an DHCP server, then that lease will be
retained after the install is done, so that the first boot of the
system will attempt to renew the same lease. yes implies that the IP address and hostname lease
should be returned to the server after the installation is complete.
In this case, the first system boot will try to get a new lease.
This is most useful when the system is being installed on a network
that is different from its final destination. This answer to the question can also be set in the configuration file
with the instl_adm command using the keyword: is_net_info_temporary
When automating system installations, the DHCP services allows systems
to get networking information without mapping the Ignite-UX configuration
files. For more information, see instl_adm(1M) and instl_adm(4). When a system boots for the first time (either after
a cold install or the first boot of a pre-loaded (Instant Ignition)
system): With HP-UX 10.20, the auto_parms and set_parms tools (they let you configure the system identity and
basic configuration parameters) will invoke the dhcpclient, which will broadcast out to find a DHCP server.
The server, in turn, provides a default set of networking parameters. With HP-UX 11.0, you are asked if DHCP should be enabled and used
(by set_parms). The default is to not use DHCP. In both cold install and a first boot of a pre-loaded system,
if the user chooses not to use the IP address given by the DHCP
server, the tool will inform the DHCP server that it can release
the lease on it and give it to someone else. At each system boot: If a client system was initially set up using an IP address
that was leased by a DHCP server, that client will check to ensure
that the lease is still valid at each boot. In addition, the system
will start a daemon process (dhcpclient -m) that will maintain and renew that lease while
the system is running. If a system cannot contact the DHCP server from which it originally got
the IP address lease, it will try to contact other DHCP servers
in order to determine if it has been moved to a different network.
If this is the case, the system will write a message to the auto_parms log file (/etc/auto_parms.log) indicating that it has detected a move to a
new subnet and that it is attempting to request a new lease. If
the new lease request is successful, new networking configuration
values supplied by the DHCP server will automatically be applied.
Enabling
DHCP on a System Not Initially Configured with DHCP | |
If a system has been set up without using DHCP, but you would
like to start using it, the following steps may be taken. | | | |  | NOTE: The system's hostname and IP address may change based
on what the DHCP server assigns to it the first time it boots. | | | | |
There are two methods for enabling DHCP on a system that is
not currently using it: Enable DHCP using SAMAs root, run: sam Double-click Networking and Communications Double-click Network Interface Cards Highlight the card on which you wish to enable DHCP. Click Actions -> Configure Click Enable DHCP | | | |  | TIP: If Enable DHCP appears grayed-out, use the alternate method below. | | | | |
Click OK and exit SAM.
Your system will now begin using DHCP after the next reboot.
Please note that all of the current networking parameters will be
overridden with new values supplied by the DHCP server. If
for some reason the system cannot contact a DHCP server during the
next reboot, it will continue to use its current networking parameters. If you suspect that your system had problem contacting the
DHCP server, examine /etc/auto_parms.log to determine if the lease request was successful. Alternate method You can also enable DHCP over a particular network interface
using a text editor such as vi or emacs to edit the /etc/rc.config.d/netconf file. In the header of this file, you will find some
brief instructions regarding a variable named DHCP_ENABLE. This variable is tied by an index number to an
individual network interface. For example: INTERFACE_NAME[0]=lan0
IP_ADDRESS[0]=15.1.50.76
SUBNET_MASK[0]=255.255.248.0
BROADCAST_ADDRESS[0]=""
DHCP_ENABLE[0]=1 Here, the variables are instructing the system to use the lan0 interface when attempting to contact a DHCP server.
Similarly, if the lease request is successful, the above IP_ADDRESS variable would be updated to reflect the new value
supplied by the DHCP server. If the DHCP_ENABLE variable was set to 0 or if the variable did not exist, no DHCP operations
would be attempted over the corresponding network interface. As noted in the first method of enabling DHCP, if the variable DHCP_ENABLE does not exist for a particular interface, SAM
will display a grayed out DHCP enable button. In this case, you will need to add the variable definition
to a specific interface variable block. As an example, you would
need to add DHCP_ENABLE[2]=1 to the following interface variable block in order
to enable DHCP on the lan1 interface: INTERFACE_NAME[2]=lan1
IP_ADDRESS[2]=15.1.50.89
SUBNET_MASK[2]=255.255.248.0
BROADCAST_ADDRESS[2]="" The contents of /etc/rc.config.d/netconf for this definition block should now look like the following: INTERFACE_NAME[2]=lan1
IP_ADDRESS[2]=15.1.50.89
SUBNET_MASK[2]=255.255.248.0
BROADCAST_ADDRESS[2]=""
DHCP_ENABLE[2]=1 Correspondingly, you could disable DHCP over a particular
interface by setting the variable to 0. Again, as in the first method, the system will only begin
using DHCP after the next reboot. DHCP
Usage Examples | |
To enable a DHCP server to respond only to specific clients
during an installation, use instl_adm to configure specific dhcp_class_ids. Your situation might fall into one of these categories: The network has a DHCP server that
manages the whole network, and the clients doing installations will
be using the addresses from this server permanently. In this case,
do nothing since this line is entered in INSTALLFS file by default: is_network_info_temporary=false The network has a DHCP server, but the user would
like to manage a small group of temporary IP addresses, just for
use in doing installations, and the clients will get reassigned
new addresses when deployed. Set up DHCP on Ignite-UX server. Use a unique dhcp_class_id in both the dhcptab and the 8KB config file. This dhpc_class_id could include the server's hostname. In this case,
enter the following in INSTALLFS using instl_adm: is_network_info_temporary=true Enter your class ID as the following in the dhcptab
and INSTALLFS: dhcp_class_id If you have a non-HP server that does not recognize dhcp_class_id, specify the server using the dhcp_server keyword instead.
The user would like to setup the Ignite-UX server
as a "departmental" DHCP server, in which case the IP address leases are
permanent, but they will be isolated to the department's DHCP server. Set up DHCP on the Ignite-UX server. Enter this line: is_network_info_temporary=false And enter your class ID as the
following in the dhcptab and INSTALLFS: dhcp_class_id (Or use the dhcp_server keyword as explained in the previous Step 3 above.)
Use a unique dhcp_class_id in both the dhcptab and the INSTALLFS file. This dhcp_class_id could have the server's hostname in it. You want to start using DHCP with this server managing
the whole network. Refer to the preceding sections, /usr/sbin/sam, and the sam(1M) manpage
for this procedure.
For more information, see the setup_server(1M) and bootpd(1M) manpages. Using
bootptab as an Alternative to DHCP | |
If you want to have more control over the allocation of IP
addresses and their mappings to your clients, you can configure
entries in /etc/bootptab for each client. Because BOOTP protocol is a subset of DHCP
protocol, the client's request for a DHCP server will be satisfied with
the BOOTP response. If you also specify a boot-file (bf) of /opt/ignite/boot/boot_lif in the bootptab entries, then you do not need any additional
entries in /etc/opt/ignite/inst_boottab. In this case, you would then boot the clients using boot lan instead of boot lan install. Only clients known in /etc/bootptab would be able to boot if you do not use instl_boottab. A minimal example /etc/bootptab entry is shown below (use your own hostname, IP address,
hardware address, and subnet mask). Other networking information
may also be specified here or via instl_adm. Specify the Ignite-UX server's IP address with
the instl_adm -t option. sysname:\
hn:\
vm=rfc1048:\
ht=ether:\
ha=080009352575:\
ip=15.1.51.82:\
sm=255.255.248.0:\
bf=/opt/ignite/boot/boot_lif Background
Information on DHCP Design The DHCP protocol is implemented as extensions to the BOOTP protocol,
and in fact the HP-UX DHCP server daemon and the BOOTP daemon are
the same: bootpd. This daemon reads two configuration files: /etc/bootptab and /etc/dhcptab. The mapping of systems to IP addresses and lease time information
is kept in the DHCP database file /etc/dhcpdb. Some amount of management of this database is provided
by the dhcptools command. On the client side, a command called /usr/lbin/dhcpclient is used to contact the server to get an IP address lease.
This command has the ability to broadcast out onto the network prior
to the network interface being enabled. The dhcpclient also serves as a daemon process that sleeps until
the time that it needs to renew the IP address lease, at which time
it will re-contact the server where it got the original lease in
order to extend it. The dhcpclient command is not intended to be run by users directly, and
is called by other tools during system bootup and installation. See the auto_parms(1M)and dhcpdb2conf(1M) manpages
for more information regarding the networking parameters which DHCP
can supply. More general information on DHCP can be found in the following locations: |
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