1. What is DHCP?
DHCP stands for "Dynamic Host Configuration Protocol".
2.What is DHCP's purpose?
DHCP's purpose is to enable individual computers on an IP network to extract
their configurations from a server (the 'DHCP server') or servers, in particular,
servers that have no exact information about the individual computers until they
request the information. The overall purpose of this is to reduce the work
necessary to administer a large IP network. The most significant piece of
information distributed in this manner is the IP address.
3. Can DHCP work with AppleTalk or IPX?
No, it is too tied to IP. Furthermore, they don't need it since they have always
had automated mechanisms for assigning their own network addresses.
4. Who Created It? How Was It Created?
DHCP was created by the Dynamic Host Configuration Working Group of the
Internet Engineering Task Force (IETF; a volunteer organization which defines
protocols for use on the Internet). As such, it's definition is recorded in an
Internet RFC and the Internet Activities Board (IAB) is asserting its status as to
Internet Standardization. As of this writing (June 1998), DHCP is an Internet
Draft Standard Protocol and is Elective. BOOTP is an Internet Draft Standard
Protocol and is recommended. For more information on Internet standardization,
see RFC2300 (May 1998)
5. How is it different than BOOTP or RARP?
DHCP is based on BOOTP and maintains some backward compatibility. The main
difference is that BOOTP was designed for manual pre-configuration of the host
information in a server database, while DHCP allows for dynamic allocation of
network addresses and configurations to newly attached hosts. Additionally,
DHCP allows for recovery and reallocation of network addresses through a
leasing mechanism.
RARP is a protocol used by Sun and other vendors that allows a computer to find
out its own IP number, which is one of the protocol parameters typically passed
to the client system by DHCP or BOOTP. RARP doesn't support other parameters
and using it, a server can only serve a single LAN. DHCP and BOOTP are
designed so they can be routed.
6.How is it different than VLANs?
DHCP and VLANs, which are very different in concept, are sometimes cited as
different solutions to the same problem. While they have a goal in common
(easing moves of networked computers), VLANs represent a more revolutionary
change to a LAN than DHCP. A DHCP server and forwarding agents can allow you
to set things up so that you can unplug a client computer from one network or
subnet and plug it into another and have it come alive immediately, it having
been reconfigured automatically. In conjunction to Dynamic DNS, it could
automatically be given its same name in its new place. VLAN-capable LAN
equipment with dynamic VLAN assignment allows you to configure things so a
client computer can be plugged into any port and have the same IP number (as
well as name) and be on the same subnet. The VLAN-capable network either has
its own configuration that lists which MAC addresses are to belong to each VLAN,
or it makes the determination from the source IP address of the IP packets that
the client computer sends. Some differences in the two approaches:
· DHCP handles changes by reconfiguring the client while a VLAN-capable
network handles it by reconfiguring the network port the client is moved to.
· DHCP dynamic reconfiguration requires a DHCP server, forwarding agent
in each router, and DHCP capability in each client's TCP/IP support. The
analogous capability in VLANs requires that all hubs throughout the
network be VLAN-capable, supporting the same VLAN scheme. To this
point VLAN support is proprietary with no vendor interoperability, but
standards are being developed.
· DHCP can configure a new client computer for you while a VLAN-capable
network can't.
· DHCP is generally aimed at giving "easy moves" capability to networks
that are divided into subnets on a geographical basis, or on separate
networks. VLANs are generally aimed at allowing you to set up subnets
on some basis other than geographical, e.g. instead of putting everyone
in one office on the same subnet, putting each person on a subnet that
has access to the servers that that person requires.
There is an issue with trying to use DHCP (or BOOTP) and VLANs at the same
time, in particular, with the scheme by which the VLAN-capable network
determines the client's VLAN based upon the client computer's source IP
address. Doing so assumes the client computer is already configured, which
precludes the use of network to get the configuration information from a DHCP
or BOOTP server.
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