HP-UX IP Address and Client Management Administrator's Guide HP-UX 11i v2, HP-UX 11i v3
4 Configuring DHCP
This chaper describes how to configure the Dynamic Host Configuration Protocol (DHCP) servers
and troubleshoot potential problems with DHCP servers.
It discusses the following topics:
• “Dynamic Updates to the DHCP Server” (page 119)
• “Configuring DHCP to Assign and Distribute IP Addresses” (page 120)
• “Monitoring and Troubleshooting DHCP Operations” (page 124)
Dynamic Updates to the DHCP Server
DHCP dynamically updates the DNS server with the host name and IP address of the client. For
every client, DHCP assigns a name and IP address. It also adds an address record (A), a pointer
record (PTR), and a resource record (RR) of that client to the DNS server.
The boolean tag pcsn is used to assign a name for every IP address. When this tag is set, the
DHCP server gives priority to the name (if any) provided by the client. The name must be a fully
qualified domain name (FQDN). If a FQDN is not specified, then the DHCP server appends the
domain name (if set using the dn tag) else it appends a . (period) and updates the Dynamic DNS
server (DDNS).
Dynamic DNS Server Update Pre-Requisites
The following pre-requisites are essential for a dynamic DNS server to accept updates from the
DHCP server.
• The resource records (RR) must not exist for an add operation.
• The resource records must exist for a delete operation.
These pre-requisites are used when the DHCP server dynimically updates (by either adding or
deleting names and IP addresses) the DDNS server.
You can configure DHCP to ignore these pre-requisites by adding the sp tag to the /etc/
dhcptab configuration file.
To enable dynamic updates to the DNS server, you must configure the DHCP server along with
the DNS server. See HP-UX IP Address and Client Management Administrator’s Guide for
information on how to configure the name server and to enable dynamic updates.
NOTE: HP recommends that DHCP servers and DNS server run on the same machine for
dynamic updates.
Figure 4-1 illustrates a single HP-UX host running both the DHCP and DNS servers.
Figure 4-1 DHCP Server and DNS Server running on HP-UX
Dynamic Updates to the DHCP Server 119