DHCP as server
What is Dynamic Host Configuration Protocol (DHCP)?
Dynamic Host Configuration Protocol
(DHCP) is network protocol for
automatically assigning TCP/IP
information to client machines. Each
DHCP client connects to the centrally-
located DHCP server which returns that
client's network configuration including IP
address, gateway, and DNS servers.
Dynamic Host Configuration Protocol
(DHCP) is a network protocol that enables
a server to automatically assign an IP
address to an individual computer's
TCP/IP stack software. DHCP assigns a
number dynamically from a defined range
of numbers (i.e., a scope) configured for a
given network.
Almost all wireless access points, many
wired Ethernet routers, and computers
running Internet Connection Sharing have
built-in DHCP servers. While this makes
configuration of a small network easier, it
can cause problems when the DHCP
servers are used in larger networks. For
this reason, Indiana University prohibits
individuals and departments from setting
up local DHCP servers on the IU network.
Client computers configured to use DHCP
for IP assignment do not need to have a
statically assigned IP address. In addition,
they generally do not need to have
addresses configured for DNS servers or
WINS servers, as these are also set by the
DHCP server
Sequence
A user turns on a computer with a DHCP client.
The client computer sends a broadcast request (called a DISCOVER or
DHCPDISCOVER), looking for a DHCP server to answer.
The router directs the DISCOVER packet to the correct DHCP server when the
server resides outside the network.
The server receives the DISCOVER packet. Based on availability and usage policies
set on the server, the server determines an appropriate address (if any) to give to the
client. The server then temporarily reserves that address for the client and sends
back to the client an OFFER (or DHCPOFFER) packet, with that address information.
The server also configures the client's DNS servers, WINS servers, NTP servers, and
sometimes other services as well.
The client sends a REQUEST (or DHCPREQUEST) packet, letting the server know
that it intends to use the address.
The server sends an ACK (or DHCPACK) packet, confirming that the client has a
been given a lease on the address for a server-specified period of time.
Dynamic vs Static
Clients : dynamic
Servers : static
Static dynamic assigned ip ?
Admins ?
Special use ...
Split scope static and dynamic
Why you need DHCP server?
DHCP is useful for fast delivery of client network configuration. When configuring the
client system, the administrator can choose DHCP and not have to enter an IP
address, netmask, gateway, or DNS servers. The client retrieves this information
from the DHCP server.
DHCP is also useful if an administrator wants to change the IP addresses of a large
number of systems. Instead of reconfiguring all the systems, he can just edit one
DHCP configuration file on the server for the new set of IP address.
If the DNS servers for an organization changes, the changes are made on the DHCP
server, not on the DHCP clients. Once the network is restarted on the clients (or the
clients are rebooted), the changes will take effect.
if a laptop or any type of mobile computer is configured for DHCP, it can be moved
from office to office without being reconfigured as long as each office has a DHCP
server that allows it to connect to the network.
Installation on debian
Apt-get update
Apt-get install dhcp3-server
/etc/dhcp3/dhcpd.conf
option domain-name "test1.com";
option domain-name-servers 192.0.0.1, 194.2.0.50;
option routers 192.0.0.151;
default-lease-time 3600;
subnet 192.0.0.0 netmask 255.255.255.0
{
arrange 192.0.0.200 192.0.0.254;
}
Static DHCP config
host hostname
{
hardware ethernet 00:B0:CF:8B:49:37;
fixed-address 192.0.0.19;
}
Restart daemon
/etc/init.d/dhcp3-server restart
Verify working
cd /var/log
tail –f messages
Ipconfig or ipconfig on client pc’s
RFC information
http://www.faqs.org/rfcs/rfc2131.html
http://www.faqs.org/rfcs/rfc2132.html