The Dhcp (Dynamic Host Configuration Protocol) Client - Digi PortServer CM User Manual

The DHCP (Dynamic Host Configuration Protocol) Client

DHCP is a protocol that allows network administrators to assign IP addresses automatically to network
devices. Without DHCP (or a similar protocol like BOOTP), each device would have to configured
manually. DHCP automatically sends a new IP address to a connected device when it is moved to another
location on the network. DHCP uses the concept of a fixed time period during which the assigned IP address
is valid for the device it was assigned for. This "lease" time can vary for each device. A short lease time can
be used when there are more devices than available IP numbers. For more information, see RFC 2131.
To activate the DHCP client on the Ethernet Interface, set the global parameter conf.dhcp_client to 1. All
other parameters related to the Ethernet Interface (conf.eth_ip, etc.) should be commented. If the IP
addresses of the PortServer CM or the default gateway are changed, the PortServer CM will adjust its
routing table accordingly. You may use an alternative command, "netconfig", to configure network
parameters.
To disable the DHCP client, set the parameter conf.dhcp_client to 0. Do not forget to uncomment the
Ethernet parameters mentioned in the previous paragraph.
Two files are related to DHCP:
• /bin/handle_dhcp - the script which is run by the DHCP client each time an IP address negotiation takes
place.
• /etc/network/dhcpcd_cmd - command which activates the DHCP client (used by the digi_ras program).
Its factory set contents are:
/sbin/dhcpcd -c /sbin/handle_dhcp
The dhcpcd command has other options which can be used on the command line. They are:
• D This option forces dhcpcd to set the domain name of the host to the domain name parameter sent by
the DHCP server. The default option is to NOT set the domain name of the host to the domain name
parameter sent by the DHCP server.
• H This option forces dhcpcd to set the host name of the host to the hostname parameter sent by the
Linux Basics
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