Dns server


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Dns server

  1. 1. DNS SERVER (Domain Name System)DNS ConceptThe DNS stands for Domain Name System. It works on 53 no. port. DNS is used toresolve name to IP address of the host computer. DNS is also called Database whichstores host records. DNS is available in Windows Server 2000 and Windows Server 2003operating system. DNS is introduced in 2000 with Window Server 2000. DomainName is Hierarchal Structure.Difference between NetBIOS Name and Domain Name NetBIOS Name Domain Name(1) It is 15 characters long. (1) It is 255 bytes long.(2)It has flat structure means no sub (2) It is Hierarchal structure , NetBIOS Names. means roots, top level Domains, second level Domains and host Computers.(3)The primary method to resolve (3) The primary method to NetBIOS over TCP/IP is WINS resolve name to IP address Server in previous Win 2000. of the host computer is DNS Server. FQDN www.yahoo.com . Host Second Top Root Computer Level LevelDNS Lookup Types: -By default, DNS has two Lookup types (i) Forward Lookup (ii) Reverse Lookup(i) Forward Lookup The forward lookup is used to store zones, which are responsible for resolve name to IP address of the Host computer. Under forward lookup type, we can create or store Primary Zone, Secondary Zone, and Stub Zone.
  2. 2. (ii) Reverse Lookup Reverse lookup is used to resolve IP address to name of the Host computer. This is very rarely configure because mostly it is used for in troubleshooting purpose in the NS Lookup.Zone Types: -DNS has three types of zones(i) Primary Zone(ii) Secondary Zone(iii) Stub Zone(i) Primary Zone In DNS server, we have to create zones under forward lookup type to configure the DNS server. Zone is also called Database, which stores Host records of the computer (NetBIOS Name and IP address). Primary Zone has read and write access. We can update data directly in this zone. This zone is available on first DNS server in the network or we can say this Zone is available on Primary DNS server. It keeps original data. This zone is also responsible for store Host records and resolve name to IP address.(ii) Secondary Zone This zone is also available under the forward lookup type. We can configure this kindof zone on secondary DNS server. It has read only access. You can not update datadirectly on this zone. It has copy of Primary zone. We can configure secondary DNSserver with Secondary zone for the purpose of fault tolerance.For e.g:- we can configure secondary DNS server with secondary zone with AdditionalDomain Controller. Zone and Data is replicated from Primary DNS server to secondaryDNS server by using zone transfer option process. It keeps copy of Primary original dataor Primary zone.(iii) Stub Zone Stub zone does not provide any kind of service like Primary and Secondary zone. Itstores special kind of records like NS record (Name of Server) and SOA record (Start ofAuthority).Records types:- (i) A Record [Host Record] (ii) Alias Record ( c Name ) (iii) MX Record [Exchange server, Mail server, @domain name (e-mails) ] (iv) NS Record - Name of Server (v) SOA Record - Start of Authority (vi) SRV Record - Service Location Record
  3. 3. Installation of DNS Server (1) log on as a Administrator (2) go to control panel -> Add/Remove Programs -> Add/Remove Components -> Network Services -> then click on Detail button -> then check the check box of DNS. (3) Click ok. (4) Click next to install the DNS server. You can access DNS server from Administrator Tools.DNS Suffix is used to resolve Name to IP Address of the Host Computer. It is also usedto register Host Records of the client computers in DNS server dynamically. In real means DNS Suffix is the name of the Primary Zone configured in thePrimary DNS server.Steps to assign DNS Suffix (1) Log on as Administrator. (2) Configure TCP/IP. IP Address, Subnet Mask and Preferred DNS IP Address. (3) Now right click on My Computer icon then Properties -> Computer Name Tab -> Change button -> More button. (4) In the Primary DNS Suffix text box. Type the name of the DNS Suffix. (5) Click ok and restart your computer.To make member of DNSOn workgroup computer, Fill Suffix name of Domain and Restart PC or type commandon Command Prompt C:>ipconfig/registerdns.Dynamic UpdatesDynamic Updates are updates which are registered in DNS server dynamically. HereDynamic updates are Host records of the client computer (Name & IP Address). Theseupdates are registered in DNS server dynamically with the help of DNS Suffix. When your DNS server accepting Dynamic Updates then your DNS server iscalled DDNS (Dynamic DNS). We can also set Dynamic Update acceptance behavior of the DNS server, inwhich we have three options:-(i) Secure only In this option only active directory clients can register their Host Record in DNSserver.(ii) Secure and Non-Secure only
  4. 4. In this option active directory clients and workgroup clients, Both can able to register their Host record in DNS server.(iii) Do not Allow In this option no one can register their Host record in DNS server. You can also change these options by zone properties.DNS with Active DirectoryDNS server plays a very important role in Domain Environment. We can also say ActiveDirectory is tightly integrated with DNS server or DNS is a backbone of ActiveDirectory. Active Directory can not work without DNS server. When we install Active Directory with DNS server then A.D registers its DomainName in DNS server, when we join clients in Domain Environment then we have toprovide IP Address of the DNS server to our client computers. First request goes to DNSserver. DNS server locates the Domain Controller and the request shifted to ActiveDirectory. So in this way client computers join Domain environment.Protocol/Port No.=> Protocol used in Active Directory is LDAP (Light Weight Directory Access Protocol)and the Port no. is 389.DNS with WANTop level Domain.Com.Edu.Net.Co.in.Org.Ca.Uk.MilRoot ServerWe have 13 Root servers. This is available on the top of the Hierarchal Structure inDomain Name System. Microsoft provides the name & IP Address of Root Servers in theDNS server. When a DNS server receives a query from a client, First of all, it will tryto resolve the query. if it has no answer then DNS server go to Root server on the Internetby using Root Hints (List of Name & IP Address of Root Servers).
  5. 5. Query Type(1) Recursive Query(2) Iterative Query(3) Referral Query(1) Recursive Query Client to DNS(2) Iterative Query DNS performs query on behalf of its clients.(3) Referral Query Appro: answer provided by Root and Com.When client receives proper answer from DNS Server then one Recursive Query iscompleted. The whole process which is performed on behalf of client is called Recursion.By default, Recursion option is enabled in DNS server.Types of DNS Server(1) Primary DNS Server(2) Secondary DNS Server(3) Cache Only DNS ServerPrimary DNS ServerThis is a first DNS Server in the network. It contains original data. It has Primary Zoneunder forward lookup.Secondary DNS ServerThis is a second DNS server in the network also act as a Backup Server. We can also saySecondary DNS server is used to provide fault tolerance in the network. It has SecondaryZone under the Forward Lookup Zone and Data is replicated from Primary to SecondaryDNS server by Zone transfer process. It has read only access. Secondary DNS serverqueried to its master server for new updates after every 15 minutes.Cache Only DNS serverThis is the type of DNS server. It has no Zone. But it has Cache, Root Hints and oneanother thing Forwarders. There is no additional configuration required in Cache Only server. Wewill just install DNS role in the computer.
  6. 6. Between two offices (Branch office and Head office) But in this case we have to configure Forwarders. In which we will provide DomainName and IP address of DNS server, Which is responsible for this Domain Name Zone.C:>ipconfig/flushdnsClear your cache and read the correct information from your DNS.
  7. 7. DHCP ConceptDHCP stands for Dynamic Host Configuration Protocol. It is used to provide or assignIP v4 addresses to the configure clients within the same network or between two subnets. In window server 2003, DHCP server is not installed by default. Differencebetween static IP address and dynamic address. Static IP address Automatic IP address (DHCP)(1) More time consuming practice. (1) Very less time required.(2) We have to maintain a list. (2) No need, list is maintained by DHCP.(3) If wrong information is delivered then (3) No chance to deliver wrong may be communication problem occurred. Information.(4) If same information delivered again then (4) No chance. may be IP address conflict with each other.(5) More overhead on administrator. (5) Less overhead on administrator.(6) If computer is shuffling from network then (6) In case shuffling, no problem of may be communication problem occur. Communication.DHCP Server workingDHCPStatic IP Scope Scope Name IP address Start IP address End IP address Subnet mask Exclude the IP from distribution Router IP address Parent Domain Name (DNS Suffix) DNS IP address WINS IP address Lease
  8. 8. DORA ProcessDHCP Server is used to provide IP address. We can configure DHCP Server by making ascope. In which we can provide lots of information, which is assigned to the clientcomputer. A DHCP Server has always Static address. When we configure our clientcomputer obtain IP address automatically then a DORA process communication isperformed between DHCP Server and DHCP Client. (1) DHCP Discover When client computer is DHCP enabled then it will start finding DHCP Server by using broadcast communication with the broadcast message packet. The information is attached by client is his NetBios Name, mac address, s port, d port etc. This message packet is also called Discover Packet. (2) DHCP Offer When a client computer sends broadcast message in the network then DHCP server receives the DHCP Discover Packet and offer IP related information to the requesting client. (3) DHCP Request When DHCP Server offer IP address related information to the requesting client then requesting client request s the DHCP Server for IP address or IP selection request to DHCP Server. (4) DHCP Acknowledgement When DHCP Server receive the request from requesting client for IP address related information then he sends acknowledgement to the requesting client and maintain his record in its database in which IP address, NetBios Name, Lease expire date & time and Mac address which is also called Unique Id.We can see or view assigned information on client computer by using command promptwith the help of following command: -C:>ipconfig/all
  9. 9. ScopeScope has IP related information, which is used to assign to the DHCP client computersdynamically. The information is IP address, exclude the IP from distribution, router IPaddress, parent domain name (DNS suffix), DNS IP address, WINS IP & Lease etc.Creating ScopeIn one subnet we can create single scope, but in case of multiple subnet we can create twoscopes with different subnet. To create the scope, open DHCP Server.Right click on Server Local then New scope.A new scope wizard appears on screen.Scope Sub containers (i) Address Pool In this sub container, it will contain Start range IP address & End range IP address as specified by the administrator. It will also contain Excluded IP address. You can exclude more IP address or IP address range by right click on this container. (ii) Address Leases In this sub container, it will show the list of assigned IP addresses & NetBios Name of its clients, Lease expiration date & time, Unique Id which is mac address of client computer. (iii) Reservation Reservation is used to ensure that a DHCP client is always assigned the same IP address. We can bound IP address with the client computer by using client computer’s mac address. By using right click on this container, we can reserve IP address for our client computer.Super ScopeSuper scope is a scope, which is used to handle multisubnet scopes. We can configurethis Super scope when our DHCP Server is configured to provide IP address between twosubnets or we can say when we want to centralized our IP address assignment methodbetween two subnets.LeaseLease is a time duration offered by DHCP Server to the requesting client that how long aclient computer can use IP address. By default lease duration is 8 days. A client computercan renew its lease after 50% of its lease duration. At the time of renewable request ifDHCP Server is not available then the second request sends by the DHCP client at 87.5%of leased duration. We can renew leased duration manually by using followingcommands: -To renew the lease duration first of all we have to release the IP address then send therenew request. To release the IP address the command is: -
  10. 10. C:> ipconfig/release(To remove configure or lease from DHCP database)When you execute this command a release message will send to the DHCP Server torelease the information from his database. In this process client computer will use a source address. To renew the leased duration the command isC:>ipconfig/renewA New lease duration is assigned to the client computer by DHCP Server.Installation of DHCP ServerGo to control panel ->Then Add/Remove programs ->Add/Remove windows components then network services ->Then detail -> Then DHCPCheck this check box, click ok.Click Next to install the DHCP.You can access it from Administrator Tools.DHCP Domain EnvironmentIf you are going to install DHCP server in Domain environment then we have toauthorize the DHCP Server from Active Directory means no other unauthorized DHCPServer will assign IP address to the client computer.There are two methods to authorized the DHCP Server in Domain Environment (1) open DHCP Server console. Right click on server local -> then click Authorize. It will show you green sign. (2) Open DHCP console. In the left pane, Right click on DHCP icon in the top of the list then manage authorize server. A new dialog box appears on screen. Click on authorized button. Type the IP address of DHCP Server. click ok. It will show you full computer name with IP address of that computer. Click ok. Again select the IP address from the list to whom you want to authorized and click ok.DHCP in Workgroup EnvironmentIn case of workgroup environment, DHCP Server computer must be a fresh workgroupcomputer means it will not be a member of a Domain Controller otherwise it will demandyou authorized from Active Directory. But in workgroup environment every computer isindependent computer and act as server, so there is no need to authorized from ActiveDirectory.