Name Resolution

HOST Names Characteristics:

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Can be up to 256 characters Host name may be the same or different than the NetBIOS name. No longer case sensitive. A host can have several host names.

Name Resolution Order in windows 2000 1. 2. 3. 4. 5. 6.

Local (Cache) Hosts File DNS LMHosts WINS Broadcast

TCP/IP host name resolution order: 1. 2. 3. 4. 5. 6.

local name hosts file - Specific. DNS - Specific. Request sent at 5, 10, 20, 40, 5, 10, and 20 seconds. WINS - specific. 3 NetBIOS b-node broadcasts - Standard lmhosts file - Specific. If entries in this file contain the entry "#PRE", the value of that line is loaded into the NetBIOS name cache memory and broadcasts will not be used to resolve these host name to IP addresses. When TCP/IP is initialized the lines with #PRE are loaded into memory. #INCLUDE statements may be used to embed one lmhosts file locally or on a remote computer into the main lmhosts file. Keywords: o #PRE - Preload the line information into memory (NetBIOS name cache). o #DOM - Domain name. Indicates that this machine is a domain controller. This prevents a broadcast from being sent to find the domain controller when changing a password or a user is logging onto a domain.

Two types of resolution are specific and standard. Microsoft resolves names two ways depending on whether the name is a TCP/IP host name or NetBIOS name. NetBIOS name resolution order for NetBIOS H-node: DHCP Lease Renewal After 50% of the lease time has passed, the client will attempt to renew the lease with the original DHCP server that it obtained the lease from using a DHCPREQUEST message. Any time the client boots and the lease is 50% or more passed, the client will attempt to renew the lease. At 87.5% of the lease completion, the client will attempt to contact any DHCP server for a new lease. If the lease expires, the client will send a request as in the initial boot when the client had no IP address. If this fails, the client TCP/IP stack will cease functioning. DHCP File information storage:

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WFW - \windows\DHCP.BIN (encrypted) WinNT - HKey_Local_Machine\System\CurrentControlSet\Services\Adapter\Parameter\Tcpip

DHCP Scope and Subnets One DHCP scope is required for each subnet. DHCP Relay Agents May be placed in two places:

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Routers Subnets that don't have a DHCP server to forward DHCP requests.

Client Reservation Client Reservation is used to be sure a computer gets the same IP address all the time. Therefore since DHCP IP address assignments use MAC addresses to control assignments, the following are required for client reservation:

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MAC (hardware) address IP address

Domain Name Resolutions As discussed above, Domain Name Resolution is the task of converting domain names to their corresponding IP address. This is all done behind the scenes and is rarely noticed by the user. When you enter a domain name in an application that uses the Internet, the application will issue a command to have the operating system convert the domain name into its IP address, and then connect to that IP address to perform whatever operation it is trying to do. The way the operating system resolves the domain name is based upon its configuration. For almost all operating systems the default order for Domain Name resolution is as follows:

1.

Hosts File - There is a file called the HOSTS file that you can use to convert domain names to IP addresses. Entries in the HOSTS file override any mappings that would be resolved via a DNS server.

2.

Domain Name System - This is the system used on the Internet for converting domain names to their corresponding IP addresses. Your operating system will connect to the DNS server configured on your computer and have that server return to you the IP address for the domain name you queried it with.

3.

Netbios - This only applies to Windows machines and will only be used to map names to IP addresses if all previous methods failed. This method will attempt to map the netbios name you are trying to connect to with an IP address.

It is possible though to change the order that your operating system uses when doing Domain Name Resolution. We will discuss these methods for the Windows and Unix/Linux operating systems below. Domain Name Resolution on Linux and Unix Unix and Linux have a similar default Domain Name Resolution order as Windows. The operating system will first check its /etc/hosts file and if it does not find an entry for the queried domain, it will then query its configured DNS servers. The order in which server resolves domain names can be changed by editing the /etc/host.conf file. This file determines the order that the operating system uses to resolve domain names. The line that we are concerned with is the one that looks like: order hosts, bind This tells the operating system to first check the hosts file, and if that fails, to use DNS, otherwise known as bind which is the name of the software used to make DNS requests. You can change the order the operating system uses, by changing the order line. For example if we wanted to make it so it queried DNS first and the hosts file second we would change the line to read: order bind, hosts

Currently the valid values you can place after order is hosts, bind, or nis. NIS stands for the Network Information Service and will not be covered by this article. Shutdown Event tracker

Windows Server 2003 introduces a new feature that helps keep track of the reasons for shutting down a particular server. The Shutdown Event Tracker service interrupts a server shutdown and queries the administrator about the reason for bringing down the server; it then writes an event to the logs. When a server powers off due to a power failure or a hardware failure, the Shutdown Event Tracker service asks for the reason the next time the server boots up. While useful in environments where admins track every shutdown reason, this feature can become an annoyance in other situations. However, you can disable the Shutdown Event Tracker service using the new Group Policy Management Console with Service Pack 1, which you can download from Microsoft's Web site. After downloading this tool, follow these steps: 1.

Go to Start | Administrative Tools | Group Policy Management.

2.

Navigate to the Default Domain Controllers Policy. (Go to Forest | | Domains | | Domain Controllers | Default Domain Controllers Policy.)

3.

Right-click the Default Domain Controllers Policy, and select Edit.

4.

Go to Computer Configuration | Administrative Templates | System.

5.

Double-click Disable Shutdown Event Tracker.

6.

Select Disabled, and click OK.

7.

Go to Start | Run.

8.

In the Open text box, enter gpupdate to refresh the group policy on the affected servers.

You can also reboot the machines to make your changes take effect. At the first reboot, the Shutdown Event Tracker will still be active because Windows hasn't loaded the new policy yet. AD New Features Domain Rename : This supports changing the Domain Name System (DNS) and/or NetBIOS names of existing domains in a forest, keeping the resulting forest still "well formed." Administrators have greater flexibility in changing the Active Directory structure after it is deployed. Design decisions are now reversible, which benefits organizations that may be in involved in a merger or significant restructuring. DNS Record Types Record type

Name

Description

A

Address Record

Maps a hostname to an IP address

PTR

Pointer Record

Maps an IP address to a hostname

CNAME

Alias Record

Maps an alias to a hostname

MX

Mail Exchanger Record

Specifies a mail route for a domain

NS

Name Server Record

Specifies name servers for a given domain

SOA

Start of Authority Record

Contains administrative data about a zone, including the primary name server

Record type SRV

Name Service Record

Description Maps a particular service (e.g., LDAP) to one or more hostnames