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GSW MCSE Notes Home Networking Essentials Notes NT Server 4.0 Notes NT Administration Notes

Module 11: Windows NT Network Services

Installing Network Services
Dynamic Host Configuration Protocol (DHCP)

The DHCP Server service centralizes and manages the allocation of TCP/IP configuration information by automatically assigning

to computers that have been configured to use DHCP.

The Process in Brief

Manual Configuring IP Addresses

Using DHCP to Configure IP Addresses

Advantages:

  1. Client receives valid IP address
  2. Configuration information is correct.

DHCP Requirements

A DHCP Server requires:

Note:
A Windows NT Workstation can't be a DHCP Server

A DHCP Client is supported by following operating systems:
ONLY Microsoft O/S's

The Four phase process to configure a DHCP client

Use ROSA as mnemonic

Phase

What happens

Description

1 - R IP lease request Client initializes a limited version of TCP/IP and broadcasts a request
2 - O IP lease offers All DHCP servers with valid IP addresses send an offer to client
3 - S IP lease selection Client selects IP address from first offer it receives and broadcasts request to lease the IP address
4 - A IP lease acknowledgment DHCP server that made offer responds to message and all other DHCP servers withdraw their offers. IP address is assigned to client and then an acknowledgment is sent to client. Client finishes initializing and binding TCP/IP protocol

 

Note:
If the computer has multiple network adapters, the DHCP process occurs separately for each adapter. A UNIQUE IP address will be assigned to each adapter in the computer.

 

Installing and Configuring the DHCP Server Service
Creating and Configuring a DHCP Scope

Option

Use this option to

IP Address Pool Start Address Specify first IP address that can be assigned to DHCP client. Required field.
IP Address Pool End Address Specify last IP address that can be assigned to DHCP client. Required field.
Subnet Mask Specify subnet mask to be assigned to all DHCP clients. Required field.
Exclusion Range Start Address
  • Specify first IP address to be excluded from IP addresses pool because of static IP addresses. 
  • This is important if there are static IP Addresses configured on non-DHCP clients
  • Not required field.
Exclusion Range End Address
  • Specify last IP address to be excluded from IP addresses pool because of static IP addresses.
  • This is important if there are static IP Addresses configured on non-DHCP clients
  • Not required field.
Lease Duration Unlimited DHCP leases assigned to clients will never expire.
Lease Duration Limited to Specify number of days hours and minutes that a DHCP client lease is available before it must be renewed.
Name  Name to be assigned to DHCP scope. Is displayed after IP address in DHCP Manager. Required field.
Comment Optional comments for scope.

 

Remember:
The Scope must be activated before the DHCP server can provide a DHCP client with a valid IP address. On Scope menu, click Activate.

 

Other DHCP Network Settings

Background:

Setting  up DHCP allows clients to participate in a TCP/IP network, but you probably want them to communicate with other computers beyond your subnet and beyond (i.e. the internet).

You can give the client computers additional information automatically. What information?

by setting the DHCP global and scope options.

Global options apply to all the scopes managed by the DHCP server.
Scope options apply to a single scope. For example, if you had separate DNS and WINS servers in each IP subnet, you would use scope options.

You reach Global and Scope options from the DHCP Options Menu

These are just a few of the many network settings DHCP clients have access to, all of which can be configured through DHCP Manager.

Option

Use this option to configure a

003 Router Default gateway
006 DNS Servers IP addresses for name servers for client
044 WINS/NBNS Servers IP addresses for NetBIOS name servers

Global Options

Scope Options

Possible question: Client can't see past its subnet -->means Router Scope Option containing the IP address of the local router wasn't set.

Client Options

Background on NetBIOS Names

NetBIOS name is used for NetBIOS processes to communicate with each other.

Name Resolution:

The process of converting a computer name to a media access control address (MAC address, physical address or burned-in address) is known as name resolution. Name resolution in a TCP/IP network is really a two-step process. Computer name-->IP address-->hardware address. Microsoft TCP/IP can use the following methods to resolve computer name to IP address.

NetBIOS Over TCP/IP Name Resolution Modes

General Note:
You usually have to exclude the static IP address from the automatic workings of DHCP or WINS services, and it is a pain to keep entering them if you have a large network, so it is best to limit their use.
You will have to supply a static IP address for
  • DHCP server
  • DNS server
  • Default Gateway
  • WINS server

Actually, on a small network, one computer could do all of this. So then use DHCP to dole out all the other IP addresses to all other computers.

 

Windows Internet Name Service (WINS)

 

WINS Overview

WINS is used to register NetBIOS computer names (host names or UNC names) and resolve them to IP addresses.
The WINS database is DYNAMIC
It eliminates the need for an LMHOSTS file

On a TCP/IP network a computer NEEDS an IP address to establish connections and can't do it using a NetBIOS computer name. This is the procedure:
 

WINS Server:

  1. WINS servers maintain a database that maps the NetBIOS computer names of WINS clients to their IP addresses.
  2. When WINS client requests an IP address, a WINS server retrieves the IP address from its database and routes it to the client.

  3. Requires:

    WINS Clients:

    Registers its computer name and IP address with a WINS server during system startup; it then queries the WINS server for computer name resolution.

    To be a WINS client you need two things:

    NOTICE only Microsoft Clients can use WINS, because WINS is the Microsoft implementation of the resolution of host names -->IP addresses

    1. To be one of these operating systems:

    2. The IP address of a WINS server

Note:
  • Windows based network clients can use WINS directly.
  • Non WINS computers that use broadcasts can access WINS through proxies. Proxies are WINS enabled computers that listen to name-query broadcast messages, forward the request to the WINS server, and then respond for names that are not on the local subnet.

Installing and Configuring WINS

Same procedure as with DHCP but now select Windows Internet Name Service. WINS Manager appears in Administrative Tools group only on NT server on which it is installed.

To give WINS a list of computers that have static IP addresses, you select Mappings --> Static Mappings-->Add Mappings

Configuring a WINS Client

Manually: You can manually add WINS server address to the WINS tab of TCP/IP properties dialog.

Automatically: You can configure DHCP to provide WINS server address by add and configure 044 WINS/NTNS Server and 046 WINS/NBT Node Type.

Domain Name System

DNS is a distributed database providing a hierarchical naming system for identifying hosts on Internet.

Below the root of the DNS file tree there are organizational names that classify the type of business. These are the top-level organizational names:

Name Brief Description
com commercial organizations
gov government organizations
mil Military organizations
net Networking and Internet Service Providers
org Non-commercial or non-profit organizations
int International organizations
edu Educational Institutions

 

The Domain Name Space

The DNS database is a tree structure called the domain name space.

What's a FQDN (Fully Qualified Domain Name)?

DNS computer names consist of two parts: a host name and a domain name, which combine to form the FQDN. With the exception of the root, each node in the DNS database has a name (label) of up to 63 characters.

DNS Server Service

DNS Server service is a name resolution service that resolves an FQDN to the IP address that is then used by the internetwork.

DNS Operation

The main function of DNS is to resolve domain names to IP addresses. This is known as name resolution.

DNS uses a client server model, in which DNS servers (name servers) contain information about the DNS database and make this information available to clients (resolvers)

The name resolution process is as follows finding an IP address this FQDN: widgets.universal.com

  1. Resolver (client) passes a query to local name server.
  2. Local name server sends an iterative request to one of the DNS root servers, requesting resolution of the FQDN. DNS root server returns referral to name servers that are authoritative for the com DNS domain.
  3. Local name server sends an iterative request to one of the com name servers, which responds with a referral to the universal name servers.
  4. Local name server sends an iterative request to one of the universal name servers.
  5. Universal name servers are running the DNS Server service on a computer running Windows NT Server. They are configured to use WINS to resolve the leftmost portion (host name) of the FQDN. When the universal name server receives the request from the local name server, it passes the widgets piece of the DNS name to its local WINS server for resolution. WINS returns the IP address for widgets to the universal name server, which returns the IP address of the FQDN to the local DNS server, which then sends it back to the client resolver.

Notice this done by integrating DNS and WINS:

Integrating WINS and DNS

DNS Benefits

Installing and Configuring the DNS Server Service

To Install:
Double click on the Network Program of the Control Panel. On Services tab click Add and then select Microsoft DNS Server.

To Configure:
Use DNS Manager (in Administrative Tools group) to configure and manage DNS. Following table lists the objects that can be configured:

Object

Description

DNS Resource Record (RR)
  • Principle object in DNS. 
  • The component that contains actual information elements managed by DNS
  • Three properties are common to all RR types: Owner, Class and TTL (Time to Live)
DNS Domain Node in DNS tree that holds all resource records for that domain
DNS Zone
  • Subtree of the DNS database that is administered as a single entity.
  • May contain single domain, or domain with subdomains
DNS Server Used to administer at least one DNS zone
Server List Contain DNS servers that can be administered with DNS Manager

 

Resource Record (RR) property set depends on the RR type. Next three are common.

Property

Function

Owner Identifies DNS domain or host to which the RR applies.
Class Identifies defined and standardized family of RR types. Almost all are "IN" or Internet class
TTL
(Time to Live)
Shows how long information in RR will remain valid.

 

Note:
  • DNS Server requires a static IP address
  • Servers are searched in the order that they appear in the DNS Manager

 

Configuring DNS Client:

DNS resolver functionality is included with

Integrating DNS and WINS

Differences:

DNS

WINS

Resolves Internet names to IP addresses Resolves NetBIOS names to IP addresses
Static database and manually updated whenever a new host is added or when an existing host is moved to another subnet. Dynamically database and dynamically updated
  • For clients running Microsoft operating systems and 
  • Non-Microsoft clients and hosts such as mainframes running TCP/IP and UNIX based computers
For Microsoft operating systems only

 

Computer Browser Service
The Browser Process

Browsers exist to provide networked computers with a list of the resources that are available on the networks. The steps that the requesting computer and the network browsers perform before and during a request are as follows:

  1. When each computer starts up and connects to the network, the computer announces its existence to the master browser in the workgroup or domain. If the computer has resources to share, it advertises them to the master browser.
  2. (Client to Master Browser: I'm here and this is what I have to share!)
     
  3. When the computer attempts to locate network resources for the first time, the computer contacts the master browser and retrieves a list of backup browsers.
  4. (Client to Master Browser: I want something-where do I get a list of what's available?)
  5. The computer contacts a backup browser and requests the network resource list.
  6. (Client to Backup Browser: Give me a who else in on the network)
     
  7. The backup browser responds with the list of domains and workgroups and the list of servers and client computers participating in the domain or workgroup that the computer is a part of.
  8. (Backup Browser to Client : Here's a list of who else is on the network)
  9. The computer contacts the server, domain controller, or workstation to request the list of resources shard by that entity.
  10. (Client to Resource holder: What stuff do you have to share?)
  11. That computer returns a list of resources to the requesting computer. Resources may now be selected by the client and a session established between the client and the share provider
  12. (Resource holder  to Client : Here's the stuff I have to share. Connect to it if you can, depending on permissions I've set.)
Browser Types

Computers running Windows NT can perform any of the Browser service roles.

Browser type

Description

Domain Master Browser
  • There is only one Domain Master Browser in the domain, and it is the PDC
  • collects and maintains the master list of available network servers and names of other domains and workgroups
  • distributes this list to master browser of each subnet in domain
Preferred Master Browser
  • You can designate a computer on the network to be the preferred master browser. When this computer joins the network, it announces itself as the Master Browser.
  • If the network already has a Master Browser, it will force an election that reevaluates the roles of computers as browsers in the network.
  • The computer that is designated as the preferred master browser will win the election unless another computer is the primary domain controller or more than one computer is designated as the preferred master browser.
  • To set a computer to be the Preferred Master Browser:
    • Navigate in the registry to the following key:

HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services

Browser\Parameters
     Set the value of 'IsDomainMaster' to 'Yes'. 

Master Browser
  • There is only one Master Browser for each workgroup or subnet of a domain. In a domain that spans multiple subnets, each subnet has it's own Master Browser that reports to the Domain Master Browser 
  • collects and maintains master list of available network servers in workgroup or subnet
  • receives info about other workgroups, domains and subnets from domain master browser and incorporates this in the list
  • distributes this list (browse list) to backup browser
  • NOTE: only one Master Browser can exist in a workgroup or domain, except in the case of a TCP/IP internetwork. Because TCP/IP does not route broadcasts, the browsing process will not reveal shared resources through routers. Therefore, a master browser must exist in each TCP/IP subnetwork, with the PDC acting as a coordinating or Domain Master Browser.
Backup Browser
  • receives copy of browse list from master browser
  • distributes list to browser clients upon request
Potential Browser
  • not a browser server but is capable of becoming backup or master browser if instructed by master browser or in absence of other browser servers
Non-Browser
  • configured that it will not maintain browse list
  • peer-to-peer networked computers are commonly non-browsers despite their having server services.

 

Browser Elections

Elections happen when a master browser for the network or subnetwork can't be found.

Browser Criteria
Configuring the Browser Role

\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Browser
\Parameters\MaintainServerList:

These are the possible value in this key:

Value

Use this value to configure the computer to

Yes
  • Attempt to become browser server
  • default for domain controllers
No
  • Never participate as browser server (computers which are frequently off line such as mobile computers)
Auto
  • Possibly be a browser server
  • This is the default for non PDC or BDC Windows NT Server/Workstations

 

Trouble Shooting

 

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E-mail Me! Comments and suggestions? E-mail me at grantwilson21@yahoo.com
I'm sorry, but I can't answer specific network-related, or exam-related questions.
Last Updated: August 6, 2001 Grant Wilson, Edmonton, AB Canada