For 10.20, dhcpclient can be called to get a DHCP
lease from a DHCP server (there is a DHCP server on HP-UX
starting with 10.10 and other vendors also produce DHCP
servers). This information includes an IP address and subnet
mask that the machine should use, as well as other optional
information, such as a DNS server and/or NIS server. DHCP is
defined in RFC's 1541, 1542, 1533, and 1534; these
definitions have been updated in later versions of the
standards documents.
dhcpclient is only intended to run if it is invoked by
auto_parms or by Cold Install (that is, it is not intended to be run
directly). It will not be invoked on diskless systems,
but will be invoked on systems where DHCP_ENABLE[0] is set to 1
in /etc/rc.config.d/netconf. Cold Install will offer you
the address that dhcpclient gets from a server, but if you
reject it, Cold Install will tell dhcpclient to
tell the server that the client does not want the address.
Addresses can be given to the client permanently or they can be
leased for a finite time by the server. The client will
be invoked by auto_parms at system start up and the lease
will be extended if appropriate (dhcpclient might also be asked
to keep extending the lease as needed while the system remains
up).
Impact |
 |
Currently, Cold Install and Instant Ignition require the machine's
user to manage their own IP address. While you can still
manually manage your own IP address, you can now allow Cold
Install or Instant Ignition to query a DHCP server to get your
IP address so that the IP address can be centrally managed on
a server. Other configuration information (such as hostname and
various server addresses) can also be obtained from the server in
the same way.
With the introduction of DHCP support in both the system installation
tools and in the set_parms utility (via auto_parms),
new systems can be easily added
to a network. DHCP allows for dynamic IP address, hostname
allocation, and IP lease management, as well as supplying general
network information such as default route, netmask, NIS domain,
DNS server, and so on.
Performance |
|
Performance is only potentially impacted at system start up.
If Cold Install or auto_parms calls dhcpclient, dhcpclient
will attempt to contact a DHCP server. This does not usually
take long if there is a server, but it can take long if the network is busy.
However, if there is no server, the process will be slowed.
In this case, dhcpclient will take time to timeout.
When dhcpclient is invoked, the amount of time that dhcpclient
takes between retries and how many times it retries to contact
a server can be specified on the command line.
Alternatives |
|
If DHCP_ENABLE[0] is set to 0 in /etc/rc.config.d/netconf,
the client should not be invoked by auto_parms.
If running Cold Install, you can choose to not use the
address offered by Cold Install via dhcpclient. Cold Install
will then set DHCP_ENABLE[0] to 0 and tell dhcpclient to
give the address back to the DHCP server.
Configuration |
|
If DHCP_ENABLE[0] is set to 0 in /etc/rc.config.d/netconf,
the client should not be invoked. If DHCP_ENABLE[0]
is set to 1, dhcpclient should be invoked at system start up.
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