Transcript cxTesting TCP/IP with Ping

Module 10A:
The Dynamic Host
Configuration Protocol
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 Overview

Describe the function of DHCP.

Explain how a DHCP client obtains IP addresses from a DHCP
server.

Install DHCP in an internetwork.

Configure a DHCP scope for multiple subnets.

Configure DHCP scope options for multiple subnets.

Enable a computer to be a DHCP client.

Use the IPCONFIG utility to view IP configurations, and to renew or
release a lease.

Backup and restore the DHCP database.

Use the JETPACK utility to compact the DHCP database.
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Testing TCP/IP with Ping
1
Start
Ping 127.0.0.1
(Loopback Address)
2
Ping IP Address
Of Your Computer
3
Ping IP Address of
Default Gateway
4
Ping IP Address of
Remote Host
End
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 What Is DHCP?
Non-DHCP
Client
DHCP
Client
IP Address2
DHCP
Client
IP Address1
DHCP
Server
DHCP Database
IP Address1
IP Address2
IP Address3
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What Is DHCP?

The Dynamic Host Configuration Protocol (DHCP)
centralizes and manages the allocation of TCP/IP
configuration information by automatically assigning IP
addresses to computers configured to use DHCP.
Implementing DHCP eliminates some of the
configuration problems associated with manually
configuring TCP/IP.
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What Is DHCP?
Each time a DHCP client starts, it requests IP
addressing information from a DHCP server, including:

IP address

Subnet mask

Optional values, such as a default gateway address,
Domain Name Server (DNS) address, DNS Domain Name
and NetBIOS Name Server address.
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What Is DHCP?

When a DHCP server receives a request, it selects IP
addressing information from a pool of addresses
defined in its database and offers it to the DHCP client.
If the client accepts the offer, the IP addressing
information is leased to the client for a specified period
of time.

If there is no available IP addressing information in the
pool to lease to a client, the client cannot initialize
TCP/IP.
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What Is DHCP?
Note:

DHCP is defined in RFCs 1533, 1534, 1541 and 1542.
DHCP is an extension of the BOOTP protocol (RFC 951)
for automatically assigning IP address information to
diskless clients. All DHCP communication is performed
over UDP ports 67 (BOOTP client) and 68 (BOOTP
server). Windows NT Server 3.51 supports DHCP, an
extension of BOOTP, but it is not a BOOTP server for
BOOTP clients.
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Why Use DHCP?


Manual Approach

Difficult to trace the source of a problem

Communication problems from mistyped information

Administrative overhead: computer relocation
Dynamic Approach (DHCP)

Client IP address is automatically leased from DHCP
server

All required configuration information is supplied

Configuration problems are eliminated
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Why Use DHCP?

To understand why DHCP is beneficial in configuring
TCP/IP on client computers, it is useful to contrast the
manual method with the DHCP method
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Configuring TCP/IP Manually

Currently, installing TCP/IP on a client requires careful configuration of an
IP address, subnet mask, and default gateway before the client can
communicate with other clients and servers. The configuration information
required is not information that the typical network user will have
knowledge of.



If a user installing TCP/IP randomly picks an IP address instead of getting
a valid IP address from the network administrator, it can lead to network
problems which can be very difficult to trace to the source.
An error in typing one of the numbers for the IP address, subnet mask, or
default gateway can also lead to problems. These problems can range
from trouble communicating using TCP/IP if the default gateway or subnet
mask is wrong, to network problems with a duplicate IP address.
There will also be configuration and administrative overhead involved on
networks where clients may frequently move between subnets. The IP
address and default gateway used when a client is attached to one subnet
needs to be changed when it is attached to another subnet to be able to
communicate with network resources. This requires a valid IP address and
default gateway for the new subnet from the administrator. The user or an
administrator will need to change these configuration values on the
computer.
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Configuring TCP/IP Using DHCP

Using DHCP to automatically configure IP addressing information
means that:




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Users no longer need to acquire IP addressing information from an
administrator to properly configure TCP/IP. When a DHCP client is
started, it automatically receives, or leases, IP addressing
information from a DHCP server.
The DHCP server supplies all of the necessary configuration
information to all DHCP clients. As long as the DHCP server has the
correct configuration information, no DHCP client will be configured
incorrectly.
Additional TCP/IP configuration values, such as type of NetBIOS
name resolution and address of a Domain Name Server (DNS) can
be supplied to the client during the lease process.
The difficult to trace network problems that results from incorrectly
configured clients and servers will be a thing of the past.
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Note:

A DHCP server can not also be a DHCP client. A DHCP
server must be manually configured with an IP address.
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How DHCP Works
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How DHCP Works

The process that DHCP uses to automatically configure
a client is as follows:
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How DHCP Works
The client initializes a limited version of
TCP/IP. If the client does not have a
specific IP address to request, the client
broadcasts a DHCPDISCOVER message
to find DHCP servers and obtain a valid IP
address.
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How DHCP Works
All DHCP servers that have a valid IP
address for the client send a DHCPOFFER
message via broadcast. The client uses
the IP address from the first response
received as the IP address it will request,
unless the client is requesting a specific IP
address.
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How DHCP Works
Once the client has selected an IP address
to use, it broadcasts a DHCPREQUEST
message to the DHCP servers asking to
lease that IP address. If the IP address
requested is the result of a DHCPOFFER
message, the Request message contains a
server identifier for the server that sent the
offer.
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How DHCP Works
This DHCP server will respond to the
DHCPREQUEST broadcast, all other DHCP
servers remove their IP address offers to
the client. The DHCP server assigns the IP
address (and any other configured options)
to the client and sends a DHCPACK
(acknowledgment) to the DHCP client.
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How DHCP Works
The client finishes initializing and binding
the TCP/IP protocol. Once the DHCP
process is complete, the client is able to
use all TCP/IP services and utilities for
normal network communications and
connectivity to other IP hosts.
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How DHCP Works
Note:
If a computer has multiple network
adapters, the DHCP process occurs
separately over each adapter. A unique IP
address will be assigned to each adapter in
the computer.
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DHCP Messages and Client States
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DHCP Messages and Client States

The DHCP client can go through six different states in
the DHCP process:

Initializing

Selecting

Requesting

Bound

Renewing

Rebinding
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DHCP Messages and Client States

In these states, DHCP uses seven messages to
communicate between the DHCP client and server.

DHCPDISCOVER (Client to Server)

DHCPOFFER (Server to Client)

DHCPREQUEST (Client to Server)

DHCPACK (Server to Client)

DHCPNAK (Server to Client)

DHCPDECLINE (Server to Client)

DHCPRELEASE (Client to Server)
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The Initializing State
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The Initializing State

The DHCP client is in the Initializing state when it is
trying to initialize the TCP/IP stack and it does not yet
have an IP address to request from the DHCP servers.
This state occurs the very first time the TCP/IP protocol
stack is initialized on the DHCP client computer. It also
occurs if the client is denied the IP address it is
requesting or the IP address it previously had was
released
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The Initializing State

When the DHCP client is in the Initializing state, its IP
address is 0.0.0.0. It's first task is to determine an IP
address that it can use. It does this by broadcasting a
DHCPDISCOVER message over UDP port 67. The
DHCPDISCOVER message contains the DHCP client's
media access control (MAC) address and computer
name.

Since the DHCP client does not yet have an IP address
and does not know the IP address of any DHCP servers,
the source IP address for the DHCPDISCOVER
broadcast is 0.0.0.0 and the destination is
255.255.255.255.
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The Selecting State
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The Selecting State

All DHCP servers that receive the DHCPDISCOVER
message and have a valid IP address for the DHCP
client will respond with a DHCPOFFER message over
UDP port 68. The DHCP servers send their DHCPOFFER
messages via broadcast since the DHCP client does not
yet have an IP address. This message contains the
DHCP client's MAC address, an offered IP address,
appropriate Subnet Mask, a server identifier (the IP
address of the offering DHCP server), and length of the
lease
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The Selecting State

When a DHCP server sends a DHCPOFFER message
offering an IP address, the DHCP server reserves the IP
address so that it will not be offered to another DHCP
client.

The DHCP client selects the IP address of the first
DHCPOFFER received.
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The Selecting State
When No DHCP Servers are Online

The DHCP client waits one second for DHCPOFFERs. If
a DHCP client does not receive a DHCPOFFER message
from a DHCP server on startup, it will retry four times (at
2, 4, 8, and 16 second intervals, plus a random amount
between 0 and 1000 milliseconds). If a DHCP client does
not receive a DHCPOFFER after its four attempts, it will
go to 'sleep' and retry again every five minutes.
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The Requesting State
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The Requesting State

In this state the DHCP client knows the IP address it
wants to lease so it broadcasts a DHCPREQUEST
message to all of the DHCP servers. The client must use
a broadcast since it does not yet have an IP address.
The data in the DHCPREQUEST message varies
depending on how the requested IP address was
obtained.
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The Requesting State

If the IP address of the client was previously known, i.e.
the computer was rebooted and is trying to lease its
previous address, then the broadcast is looked at by all
of the DHCP servers. The DHCP server that can lease
the requested IP address responds with either a
successful acknowledgment (DHCPACK) or an
unsuccessful acknowledgment (DHCPNAK). The
DHCPNAK message occurs when the IP address
requested is not available or the client has been
physically moved to a different subnet which would
require a different IP address. After receiving this
message the client returns to the Initializing state.
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The Requesting State

If the IP address of the client was just obtained with a
DHCPDISCOVER/DHCPOFFER exchange, the client
will include the IP address of the server it received the
offer from in the DHCPREQUEST message. This server
identifier causes the specified DHCP server to respond
to the request and all other DHCP servers to retract their
DHCP offers to the client. This makes the offered IP
addresses on the other DHCP servers immediately
available to the next initializing DHCP client.
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The Bound State
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The Bound State

The DHCP server responds to the DHCPREQUEST
message with a DHCPACK (DHCP acknowledgment)
message that contains a valid lease for the negotiated
IP address as well as any optional parameters
configured by the DHCP administrator. Once again, the
DHCPACK message is sent by the DHCP server via
broadcast. When the DHCP client receives the
DHCPACK message, it completes initialization of TCP/IP
and is now considered a bound DHCP client and can
use TCP/IP to communicate on the network.
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The Bound State

Note:

The DHCPDISCOVER/DHCPOFFER/DHCPREQUEST/
DHCPACK messages are sent out via MAC-level
broadcasts. For DHCP clients to communicate with a
DHCP server on a remote network, the connecting
router(s) must support forwarding DHCP broadcasts. Not
all routers support RFC 1542 (DHCP) and have this
capability and may require a software upgrade for this
support.
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
The client stores the IP address, subnet mask, and other
IP addressing information locally in one of the following
locations:


On Windows NT and Windows 95 computers HKEY_LOCAL_MACHINE\SYSTEM
\CurrentControlSet\Services\adapter
\Parameters\Tcpip
On Windows for Workgroups computers \windir\DHCP.BIN (encrypted)
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IP Lease Acknowledgment (Unsuccessful)

An unsuccessful acknowledgment is broadcast
(DHCPNACK) if:



The client is trying to lease its previous IP address and
the IP address is no longer available, or
The IP address is invalid because the client has been
physically moved to a different subnet.
When the client receives an unsuccessful
acknowledgment, it returns to the process of requesting
an IP lease.
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Note:

Whenever a DHCP server receives a request for an IP
address which is invalid according to the scopes that it
is configured with, it sends a DHCPNACK negative
acknowledgment to the client. With every negative
acknowledgment the DHCP server also records an event
in the Windows NT event log.
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The Renewing State
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The Renewing State

By default, DHCP clients first try to renew their lease
when 50% of the lease time has expired. To renew its
lease, a DHCP client sends a directed DHCPREQUEST
message to the DHCP server from which it obtained the
lease.
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The Renewing State

If permitted, the DHCP server will automatically renew
the lease by responding with a DHCPACK message.
This DHCPACK message will contain the new lease as
well as any configuration parameters so that the DHCP
client can update its settings in case the administrator
updated any settings on the DHCP server. Once the
DHCP client has renewed its lease, it returns to the
Bound state.
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The Renewing State

If a DHCP client attempts to renew its lease on an IP
address and is unable to contact a DHCP server, the use
is prompted with an error message.
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The Rebinding State
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The Rebinding State

If, for some reason, the DHCP client is unable to
communicate with the DHCP server from which it
obtained its lease, when 87.5% of the lease time has
expired it will attempt to contact ANY available DHCP
server. The DHCP client attempts to contact any DHCP
server by broadcasting DHCPREQUEST messages so
that any DHCP server can provide a new IP address
lease to the client. Any DHCP server can respond with a
DHCPACK message renewing the lease or a DHCPNACK
message that will force the DHCP client to re-initialize
and obtain an IP address lease for a new IP address.
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The Rebinding State

If the lease expires or a DHCPNACK message is
received, the DHCP client must immediately discontinue
using the IP address. However, the DHCP client will
return to the Initializing state and attempt to obtain
another IP address lease.

If the client loses its IP address, communication over
TCP/IP will stop until a new IP address is assigned to
the client. This will cause network errors for any
applications that attempt to communicate over the
TCP/IP protocol interface that has become invalid.
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DHCP Across IP Routers
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DHCP Across IP Routers

The preceding explanation of how DHCP works
assumed that the DHCP client and DHCP server were on
the same network. In a large IP internetwork, it is
desirable to place DHCP servers in strategic locations
servicing clients of multiple networks. In order for this
to occur, the DCHP messages (DHCPDISCOVER,
DHCPOFFER, DHCPREQUEST, DHCPACK/ DHCPNAK)
must be able to cross IP routers. Without the ability to
have these DHCP messages to cross IP routers, a DHCP
server would be required on each subnet for which
there are DHCP clients.
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DHCP Across IP Routers

The four broadcast-based DCHP messages
(DHCPDISCOVER, DHCPOFFER, DHCPREQUEST,
DHCPACK/DHCPNAK) are sent to the limited IP
broadcast address 255.255.255.255 and as MAC level
broadcasts. By default, IP routers will not pass any
broadcast frames but the DHCP messages are an
exception.
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DHCP Across IP Routers

Historically, DHCP is based on the BOOTP protocol, a
protocol for supplying IP address information to
diskless workstations upon system startup. In order to
have the BOOTP messages cross an IP router, a special
component was implemented on the IP router called a
BOOTP relay agent. The BOOTP relay agent recognizes
the BOOTP packets because they are addressed to the
MAC-layer broadcast address, the IP limited broadcast
address and using either UDP port 68 or 67 and then
passes these packets to the other networks to which it
is connected. The BOOTP relay agent allowed the
BOOTP servers to be on different networks than the
BOOTP client.
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DHCP Across IP Routers

DHCP is an extension of BOOTP. RFC 1542 documents
the extensions to the BOOTP protocol to support DHCP
and also specifies the changes to the BOOTP Relay
Agent that are required to support DHCP messages. In
order for a BOOTP Relay Agent to support DHCP
messages, it must be compliant with RFC 1542. Not all
routers support RFC 1542 directly, and may require a
software upgrade.
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Recording the originating network

For the DHCP server to allocate an IP address that is
proper for the network where the client is located, it
must have some knowledge of the DHCP client's IP
network ID. Since the client cannot provide this
information in its initial DHCPDISCOVER message, the
information must come from somewhere else.
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Recording the originating network

In the DHCP message packet structure is a field called
"giaddress". The purpose of this field is to record the IP
address of the router interface first encountered by the
DHCPDISCOVER and DHCPREQUEST message. The
RFC 1542 compliant BOOTP relay agent on the IP router
sees the DHCP message and inspects the giaddress
field. If it is empty, it places the IP address of the
interface which received the DHCP message into the
giaddress field.
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Recording the originating network

In the above example, when DCHP Client 1 broadcasts
the DHCPDISCOVER message, the router will record the
IP address 131.107.1.1 in the giaddress field of the
DHCP message. Once received, the DHCP server
determines that DHCP Client 1 is located on network
131.107.1.0 and sends a DHCPOFFER message from the
scope of addresses for network 131.107.1.0.
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Implementation Considerations

Before you install DHCP, ask yourself these questions:
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What IP addressing options will clients obtain from a DHCP
server?


Such as:

Default gateway

WINS server

DNS server

DNS Domain Name (Windows NT 3.51 and above)
The IP addressing options determine how to configure
the DHCP server, and whether the options should be
created for all clients in the internetwork, clients on a
specific subnet, or individual clients.
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Will all computers become DHCP clients?

If not, consider that:

Non-DHCP clients have static IP addresses.

Static IP addresses must be excluded from the DHCP
server configuration.

If a client requires a specific address, the IP address
needs to be reserved.
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Will a DHCP server supply IP addresses to multiple subnets?

If so, consider that:

Any routers connecting subnets must support RFC 1542
and act as BOOTP Relay Agents. If your routers do not
support RFC 1542, at least one DHCP server is
required on each subnet that has DHCP clients.
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How many DHCP servers are required?

Consider that:

A DHCP server does not share information with other
DHCP servers. Therefore, it is necessary to create
unique IP addresses for each server to assign to clients.
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Considerations for Implementing Multiple DHCP Servers
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Considerations for Implementing Multiple DHCP Servers

If your internetwork requires multiple DHCP servers, it
is necessary to create a unique scope for each subnet.
A scope is a range of IP addresses that are available to
be leased or assigned to clients.
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Considerations for Implementing Multiple DHCP Servers

To ensure that clients can lease IP addresses, it is
important to have multiple scopes for each subnet
distributed among the DHCP servers in the
internetwork. For example:


Each DHCP server should have a scope containing
approximately 75 percent of the available IP addresses
for the local subnet.
Each DHCP server should have a scope for each
remote subnet containing approximately 25 percent of
the available IP addresses for a subnet.
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Considerations for Implementing Multiple DHCP Servers

When a client's DHCP server is unavailable, the client can still
receive an address lease from another DHCP server on a different
subnet.

As illustrated in the graphic, Server-A has a scope for the local
subnet with an IP address range of 131.107.4.20 through
131.107.4.150, and Server-B has a scope with an IP address range
of 131.107.3.20 through 131.107.3.150. Each server can lease IP
addresses to clients on its own subnet.

Additionally, each server has a scope containing a small range of IP
addresses for the remote subnet. For example, Server-A has a
scope for Subnet-B with the IP address range of 131.107.3.151
through 131.107.3.200. Server-B has a scope for Subnet-A with the
IP address range of 131.107.4.151 through 131.107.4.200.
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Considerations for Implementing Multiple DHCP Servers

When a client on Subnet-A is unable to lease an address
from Server-A, it can lease an address for its subnet
from Server-B.
Note:

When implementing multiple DHCP servers and
distributing the address pool for fault tolerance, it is
possible to have overlapping scopes. DHCP servers
have no awareness of each other and do not
communicate with each other to ensure that they have a
unique pool of addresses for each network. With two
DHCP servers and an overlapping scope, it is possible
for the same IP address to be allocated to two different
nodes.
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DHCP Requirements

To implement DHCP, both the client and the server
require configuration.
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DHCP Requirements: Router Requirement

All routers connecting subnets with DHCP servers and
clients must support RFC 1542 and act as BOOTP Relay
Agents.
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DHCP Requirements: Server Requirements

A DHCP server requires:

The DHCP Server service configured on at least one computer
within the TCP/IP internetwork running Windows NT Server (it does
not have to be a domain controller), provided that your IP routers
support RFC 1542. Otherwise, you will need a DHCP server on each
subnet.

The DHCP server configured with a static IP address, subnet mask,
default gateway, and other TCP/IP parameters (it cannot be a DHCP
client).

A DHCP scope created on the DHCP server. A DHCP scope consists
of a range, or pool, of IP addresses that the DHCP server can
assign, or lease, to DHCP clients- for example, 131.107.3.51 through
131.107.3.200.
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DHCP Requirements: Client Requirements
A DHCP client requires:

A computer running any of the following supported operating
systems:
Windows NT Server 3.5 and above (cannot be a
DHCP server).
Windows NT Wrkstation 3.5 and above.
Windows 95.
Windows for Workgroups 3.11 running Microsoft®
TCP/IP-32 (provided on the Windows NT Server
3.5 and above CD).
Microsoft Network Client 3.0 for MS-DOS with
the real mode TCP/IP driver included on the
Windows NT Server 3.5 and above CD.
LAN Manager 2.2c included on the Windows NT
Server 3.5 and above CD. LAN Manager 2.2c for
OS/2 is not supported.
Third party DHCP client.

DHCP enabled.
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DHCP Client Platforms
Microsoft
Network Client or
LAN Manager 2.2c
Windows for
Workgroups 3.11
IP
Router
Windows NT
Workstation/
Server
Windows 2000
Windows XP
Windows 2003
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Windows
95/98/Me
Workstation
DHCP
Server
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The IPCONFIG Utility

The IPCONFIG utility is a diagnostic tool used to verify a
computer's TCP/IP configuration
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Verifying the IP Configuration

From a command prompt, type the following command
to verify a computer's IP address, subnet mask, and
default gateway:
ipconfig

From a command prompt, type the following command
to verify a computer's IP configuration for the operating
system and the network adapter:
ipconfig /all
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Use the /ALL switch and provide the following
information:
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
Host name assigned to the local computer.

IP address of any DNS Servers the local computer is
configured to use.

NetBIOS node type, such as broadcast, hybrid, peerpeer, and mixed.

NetBIOS scope ID.

Whether or not IP Routing is enabled.

Whether or not WINS proxy is enabled.

Whether or not NetBIOS resolution uses DNS.
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Use the /ALL switch and provide the following network
adapter IP configuration information:

Description of the adapter card, such as Etherlink II.

Physical address of the adapter card.

Whether or not DHCP is enabled.

IP address of the local computer.

Subnet mask of the local computer.

Default gateway of the local computer.

IP addresses of the primary and secondary WINS
servers.
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Updating a Lease

The /RENEW switch causes a DHCPREQUEST message
to be sent to the DHCP server to get updated options
and lease time. If the DHCP server is unavailable, the
client will continue using the current DHCP supplied
configuration options. From a command prompt type:
ipconfig /renew
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Releasing a Lease

The /RELEASE switch causes the DHCP client to send a
DHCPRELEASE message to the DHCP Server and give up its lease.
This is useful when the client is changing to a different network and
will not need the previous lease. After this command has been
carried out, TCP/IP communications will stop. From a command
prompt, type:
ipconfig /release

Microsoft DHCP clients do not initiate DHCPRELEASE messages
when shutting down. If a client remains shut down for the length of
its lease (and the lease is not renewed), it is possible for the DHCP
server to assign that client's IP address to a different client after the
lease expires. By not sending a DHCPRELEASE message, the client
has a better chance of receiving the same IP address during
initialization
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Backing Up and Restoring the DHCP Database

Backing Up the DHCP Database

Restoring the DHCP Database
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Backing Up the DHCP Database

By default, the DHCP database is backed up every 60 minutes.
Backup copies are stored in the
\systemroot\SYSTEM32\DHCP\BACKUP\JET directory.

The default backup interval can be changed by setting the
BackupInterval value to the appropriate number of minutes. This
BackupInterval parameter is located in Registry under the following
key:
HKEY_LOCAL_MACHINE
\SYSTEM
\CurrentControlSet
\Services
\DHCPServer
\Parameters
\BackupInterval
A copy of this Registry subkey is stored in the
\systemroot\SYSTEM32\DHCP\BACKUP directory as
DHCPCFG.
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Restoring the DHCP Database

The DHCP database can be restored either automatically or
manually. The restore process is done using any of the following
methods.

Restart the DHCP Server service. If the DHCP Server service
detects a corrupt database, it automatically restores a backup copy
of the database.

Set the RestoreFlag value to 1, and then restart the DHCP Server
service. The RestoreFlag parameter is located in the Registry under
the following key:

HKEY_LOCAL_MACHINE \SYSTEM
\CurrentControlSet \Services \DHCPServer
\Parameters

Once the database has been successfully restored, the server
automatically changes the value back to the default value of 0.

Copy the contents of the
\systemroot\SYSTEM32\DHCP\BACKUP\JET directory to
the \systemroot\SYSTEM32\DHCP directory, and then
restart the DHCP Server service.
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Note:

Using the restore procedure, the DHCP server can also
be moved to another Windows NT server computer.
Note if the files are put into a different directory or on a
new partition, you will need to edit the
....\Services\DHCPServer \parameters\DatabasePath and
BackupDatabasePath to reflect the new location.
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Reconciling the DHCP Database

With Windows NT 3.51 and later there is a new
Reconcile button in the active leases dialog which will
verify that all entries in the registry (every lease is
stored in the registry as well as the dhcp.mdb file) is
correct. More information can be found in the TCP/IP
Supplement document included in Windows NT 3.51.
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The DHCP Database Files

The following files are stored in the \systemroot\SYSTEM32\DHCP
directory:

Caution: Do not tamper with or remove these files.
File
Description
DHCP.MDB
The DHCP database file.
DHCP.TMP
A temporary file that DHCP creates for
temporary database information while the
DHCP Server service is running.
JET.LOG and JET*.LOG
Logs of all transactions done with the
database and are used by DHCP to recover
data if necessary.
SYSTEM.MDB
Used by DHCP for storing information about
the structure of the database.
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Compacting the DHCP Database

The size of the DHCP database depends on the number
of DHCP clients, the frequency that clients are moved
from one subnet to another, and the frequency that
clients renew a lease.

The JETPACK (JETPACK.EXE) utility is used to compact
the DHCP database. It is recommended to compact the
database whenever its size grows beyond 10 MB.
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To compact the database:
1.
Stop the DHCP Server service. This can be done from Control Panel
Services, Server Manager, or a command prompt. To stop the service
from a command prompt, use the following command syntax:

2.
net stop dhcpserver
From the \systemroot\SYSTEM32\DHCP directory, run the JETPACK utility
using the following command syntax (assign any filename to
temporary_name):

jetpack dhcp.mdb temporary_name.mdb
The contents of DHCP.MDB are compacted in
temporary_name, and then the temporary file is
copied to DHCP.MDB, and the temporary name is
deleted.
3.
Restart the DHCP Service from Control Panel Services, Server Manager,
or a command prompt. To restart the service from a command prompt,
use the following command syntax:

net start dhcpserver
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Review

TCP/IP Overview

TCP/IP for Heterogeneous Networking

Microsoft TCP/IP on Windows NT Server

TCP/IP Configuration Parameters

Installing Microsoft TCP/IP

Testing TCP/IP with Ping

What Is DHCP?

What Is WINS?
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Lab 10: Implementing DHCP
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