Transcript Chapter 15 PowerPoint Slides

Chapter Overview
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Understanding Windows Name Resolution
Using WINS
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Understanding Windows Name
Resolution
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Internet Protocol (IP) addresses are easily
handled by computers but are difficult for
people to remember.
Naming systems create user-friendly
identifiers for computers and other network
elements.
The naming system used by Microsoft
Windows is based on Network Basic
Input/Output System (NetBIOS).
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Understanding Windows Name
Resolution (Cont.)
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A NetBIOS name is 16 characters long with 15
usable characters.
You assign a NetBIOS name when you install the
operating system.
After adopting Transmission Control
Protocol/Internet Protocol (TCP/IP) as the default
networking protocol, Microsoft implemented
standards that define the use of NetBIOS Over
TCP/IP (NetBT).
These standards call for a mechanism that can
resolve NetBIOS names into IP addresses.
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Understanding Windows Name
Resolution (Cont.)
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Windows has introduced the following
NetBIOS name resolution mechanisms over
the years, and all are available in Microsoft
Windows 2000:
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NetBIOS name cache
Network broadcasts
LMHOSTS files
Windows Internet Name Service (WINS)
Active Directory service
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Understanding Windows Name
Resolution (Cont.)
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Early versions of Microsoft Windows NT relied on
network broadcasts and LMHOSTS files for name
resolution.
Windows NT 4 used WINS for NetBIOS name
resolution.
Windows 2000 uses Active Directory for name
resolution, which relies on the Domain Name System
(DNS) to handle name registration and resolution
tasks.
Microsoft Windows 2000 Server includes a WINS
server to support computers on the network that run
earlier versions of Windows.
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Understanding the NetBIOS Name
Cache
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All Windows computers maintain a cache of
NetBIOS names they have recently resolved, and
their equivalent IP addresses.
The computer checks the NetBIOS name cache
before using another name resolution
mechanism.
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The cache is stored in memory.
The cache is emptied each time the computer is
restarted.
To view the NetBIOS name cache, you type
nbtstat -c at a command prompt, and then
press Enter.
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Understanding Broadcast Name
Resolution
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When WINS servers are not available,
computers running pre–Windows 2000
operating systems use broadcast messages to
resolve NetBIOS names into IP addresses.
There are two main problems with the
broadcast name resolution method:
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Broadcasts are limited to the local network.
This method generates an excessive number of
broadcast transmissions on the network.
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Using LMHOSTS Files
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A HOSTS file is a text file containing a list of host
names and their equivalent IP addresses.
A computer running TCP/IP uses a HOSTS file to
discover the IP address associated with a host
name.
An LMHOSTS file uses the same concept for
NetBIOS names.
The LMHOSTS files method is superior to the
broadcast method because it is fast, it does not
generate any network traffic, and it can resolve
the NetBIOS name of a computer anywhere on a
network.
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Using LMHOSTS Files (Cont.)
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LMHOSTS files have two shortcomings:
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Someone must manually update the LMHOSTS file
when the network changes.
Each computer must have its own copy of the file.
An LMHOSTS file consists of entries
containing NetBIOS names and their
corresponding IP addresses, such as
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192.168.94.97
192.168.94.123
192.168.94.117
rhino
popular
localserv
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LMHOSTS Keywords
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You can create different types of entries in an
LMHOSTS file with the following keywords
that perform special functions:
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\0xnn: provides support for nonprinting characters
in NetBIOS names
#BEGIN_ALTERNATE: used to group multiple
#INCLUDE statements
#END_ALTERNATE: used to mark the end of an
#INCLUDE statement grouping
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LMHOSTS Keywords (Cont.)
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#DOM:<domain>: part of the computer
name-to-IP-address mapping entry that indicates
that the IP address belongs to a domain controller
in the domain specified by <domain>
#INCLUDE <filename>: forces the system to
seek the specified <filename> and parse it as if it
were local
#MH: part of the computer name-to-IP-address
mapping entry that defines the entry as a unique
name that can have more than one address
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LMHOSTS Keywords (Cont.)
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#PRE: part of the computer name-to-IP-address
mapping entry that causes the entry to be
preloaded into the name cache
#SG: part of the computer name-to-IP-address
mapping entry that associates that entry with a
user-defined special (Internet) group specified by
<name>
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Introducing WINS
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WINS is a NetBIOS name server that runs as
a service on computers running Microsoft
Windows NT Server and Windows 2000
Server.
WINS enables client computers to resolve
NetBIOS names into IP addresses by sending
a single unicast message to the WINS server,
rather than broadcast messages to the entire
network.
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Registering Names
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Name registration is the process of
establishing NetBIOS names on the network
and associating them with specific IP
addresses.
For an LMHOSTS file, name registration
occurs when the administrator manually
creates the entries in the file.
For the network broadcast and WINS
methods, name registration occurs when
each computer on the network starts.
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Windows Node Types
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The NetBIOS name registration and
resolution mechanisms used by a computer
running a pre–Windows 2000 operating
system are determined by the system's node
type.
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B node: uses only broadcasts for name
registration and resolution.
P node: uses only NetBIOS name servers for name
registration and resolution.
M node: uses only broadcasts for name
registration. For name resolution, uses broadcasts
first and switches to NetBIOS name server if the
broadcasts fail to resolve the name.
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Microsoft Node Types
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Microsoft has developed its own node types.
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Modified B node: uses only broadcasts for name
registration.
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For name resolution, uses broadcasts first and switches
to an LMHOSTS file if broadcasts fail
Default node type for a non–WINS client computer
H node: uses only NetBIOS name server (WINS)
for name registration.
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For name resolution, uses NetBIOS name servers first,
and if that fails, switches to broadcasts
Default node type for a WINS client computer
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Microsoft Node Types (Cont.)
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Microsoft enhanced H node: a variation of the H
node that adds LMHOSTS files, DNS queries, and
HOSTS files as fallbacks to the NetBIOS name
servers (WINS) and broadcasts defined in the H
node type
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Computers running Windows NT and Windows 2000 can
use all of these name resolution methods.
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Lesson Summary
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Computers running Windows use NetBIOS names
to identify themselves on the network.
To use NetBIOS names on a TCP/IP network,
there must be a mechanism to resolve NetBIOS
names into IP addresses.
There are several NetBIOS name resolution
mechanisms, including a NetBIOS name cache,
network broadcasts, LMHOSTS files, WINS, and,
for computers running Windows 2000, Active
Directory.
Windows 2000 Server includes a WINS server to
support pre–Windows 2000 clients.
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Using WINS
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System administrators should know
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The purpose and function of WINS and name
registration
How to install a WINS server
How to configure a WINS client
How to provide support for non–WINS clients by
using static mappings and by configuring a WINS
proxy agent
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Introduction to WINS
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A Windows 2000 network requires a way to resolve
NetBIOS names to IP addresses for client computers
running Microsoft Windows 98 or Microsoft Windows NT 4.
WINS is an enhanced NetBIOS name server that registers
NetBIOS computer names and resolves them into the IP
addresses needed for TCP/IP communication.
WINS also provides a dynamic database that maintains
mappings of computer names to IP addresses.
All WINS messages are sent as unicasts. This reduces
network traffic and enables the client to communicate
with a WINS server anywhere on the network.
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The WINS Name Resolution Process
1. The WINS client checks its NetBIOS name
cache to see if there is an entry for the
desired name.
2. If there is not, the client transmits a NAME
QUERY REQUEST unicast message to its
primary WINS server.
3. The WINS server searches its database, and
then returns the IP address to the WINS
client in a POSITIVE NAME QUERY
RESPONSE message.
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The WINS Name Resolution Process
(Cont.)
4. If the requested name is not in the WINS
server's database, the WINS server sends a
NEGATIVE NAME QUERY RESPONSE
message to the client.
5. If the client receives no response from the
WINS server, it switches to the secondary
WINS server.
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The WINS Name Registration Process
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When a WINS client computer is started, it
registers its NetBIOS name and IP address by
sending a NAME REGISTRATION REQUEST
message directly to its primary WINS server.
If the WINS server is available and another
WINS client has not registered the name
already, the WINS server returns a POSITIVE
NAME REGISTRATION RESPONSE message to
the client.
The WINS server also stores the client's
NetBIOS name-to-IP-address mapping in its
database.
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WINS Name Renewal
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WINS servers register all NetBIOS names for
a specified interval, the Time to Live (TTL).
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By default, the TTL is six days.
WINS clients must renew their NetBIOS
names or their leases will expire.
Each time a WINS client computer restarts
and registers its name with the WINS server,
the TTL interval is reset.
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WINS Name Renewal (Cont.)
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If a client remains logged on continuously for
half of the TTL, it begins transmitting NAME
REFRESH REQUEST messages to the WINS
server.
The WINS server replies with one of the
following messages:
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POSITIVE NAME REFRESH RESPONSE: resets the
TTL timer
NEGATIVE NAME REFRESH RESPONSE: cancels
the name registration and forces the client to
register a different NetBIOS name
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WINS Name Release
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When a WINS client computer shuts down,
the computer transmits a NAME RELEASE
REQUEST message to the WINS server.
The WINS server responds with one of the
following messages:
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POSITIVE NAME RELEASE RESPONSE: indicates
that the server has successfully released the name
NEGATIVE NAME RELEASE RESPONSE: occurs
only when the server's record shows a different IP
address than that of the requesting client
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Installing a WINS Server
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WINS is not installed by default.
You can install WINS when you install
Windows 2000 Server, or you can install it
later by using Add/Remove Programs in
Control Panel.
A WINS server should be configured with a
static IP address, subnet mask, and default
gateway; it should not use a Dynamic Host
Configuration Protocol (DHCP) server to
obtain these TCP/IP settings.
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The Windows Components Page in
the Windows Components Wizard
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Selecting WINS in the Networking
Services Dialog Box
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The WINS Server
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After you install the WINS service on a
Windows 2000 Server computer, you should
configure the server as a WINS client, with
itself as the WINS server.
When you install WINS, the WINS snap-in is
added to the Administrative Tools program
group.
You can use this snap-in to view, configure,
and manage the WINS servers on your
network.
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The WINS Snap-In
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Configuring a Windows 2000 WINS
Client
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Although Windows 2000 does not need WINS
to access resources on other computers
running Windows 2000, it does need WINS to
access resources on computers running
earlier versions of Windows.
You must also configure the WINS server to
be a client of itself.
You use the Network And Dial-Up
Connections application in Control Panel to
configure a computer running Windows 2000
to function as a WINS client.
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The Internet Protocol (TCP/IP)
Properties Dialog Box
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The WINS Tab in the Advanced
TCP/IP Settings Dialog Box
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Supporting Non–WINS Clients
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In a WINS environment, you can provide
support for non–WINS clients in two ways:
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By using static mappings
By configuring a WINS proxy agent
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Using Static Mappings
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On a network that includes non–WINS clients,
you can configure a static NetBIOS name-toIP-address mapping for each non–WINS
client.
This ensures that WINS clients can resolve
the NetBIOS names of non–WINS client
computers.
You use the WINS console on the WINS
server to configure a static mapping for non–
WINS clients.
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The New Static Mapping Dialog Box
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Configuring a WINS Proxy Agent
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A WINS proxy agent is a specially configured
WINS client computer that listens for
broadcast name registration and resolution
messages from non–WINS clients, and then
forwards these messages to a WINS server.
To configure a WINS proxy agent, on a WINS
client computer, change the EnableProxy
registry entry value to 1, and then restart the
computer.
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Lesson Summary
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WINS is a NetBIOS name server that registers
NetBIOS computer names and resolves them into
IP addresses.
WINS uses unicast transmissions, which reduce
network traffic.
WINS is included with Windows 2000 to support
clients running earlier versions of Windows.
Static mappings enable WINS clients to resolve
NetBIOS names of non–WINS computers.
A WINS proxy agent relays broadcast name
registration and resolution messages to a WINS
server.
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