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DNS

DNS. Very important to get DNS settings right on your network. DNS. Domain Name System or Domain Name Service. What is it?. It's a network service that translates names into IP addresses. What is it?.

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DNS

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  1. DNS Very important to get DNS settings right on your network

  2. DNS • Domain Name System or • Domain Name Service

  3. What is it? It's a network service that translates names into IP addresses

  4. What is it? If you are on a computer and you type google.com into a browser. Before it can connect to the Google web server it must know the IP address of the Google web server. So your computer asks DNS what’s the IP address of the Google.com web server. DNS gives back the IP address and so the computer can connect to the Google web server and get the web page.

  5. Names • Domain Names • Host Names

  6. Domain Names like • .com • .net • Google • Fbtafe • Apple • WWITLABS - here at West Wollongong TAFE you put in your user name and password and then log into a domain (that’s a Windows domain name) –but it works the same in DNS. DNS is essential in Windows domains.

  7. Host Names like • WWFG27-01 • XPFB • W2K3FB • StevesPC • GoogleWeb1 These are computer names – the first 3 are computer names in the labs. In DNS computer names are referred to as Host names.

  8. Host Names What are Hosts? – Any workstation, server, printer, router on our network. In DNS they are all known as hosts. Hosts all have a host name and an IP address.

  9. TCP/IP TCP – establishes and maintains an error free connection between 2 hosts IP – transmits packets between hosts

  10. So when we are talking DNS we are taking about hosts that have a host name and IP address and they communicate using TCPIP whether it be on a local area network or going across the internet cloud to a Telstra Mail Server, a Google web server or an Apple server.

  11. IPCONFIG/ALL

  12. History • 1969 – ARPAnet Start of the internet (4 universities started exchanging data) • Between 1969 and 1971 many more computers got added – all using IP addresses. Remembering the IP addresses and who had what IP address started to become a real problem.

  13. History • 1971 – Peggy Karp came up with a Hosts file. • It contained the host name and IP addresses. She installed that on each of the computers at the university. This meant that if a computer wanted to communicate with say a File server you could use the name – which would then use the Hosts file to look up the IP address.

  14. History • The Hosts file was adopted by the other universities so the file was regularly updated and distributed to operators at the 4 universities and any other organisations that required it.

  15. History • 1985 – first Domain Name System – it took 13 years before DNS was introduced - hundreds, probably thousands of computers had been added to the internet in that time and the Hosts file was just too difficult to work with, keep up to date, etc.

  16. Note • the Hosts file is still available today • check c:\windows\system32\drivers\etc and you will see the Hosts file

  17. How does DNS work? • DNS is a "distributed database" of names and IP addresses. It's distibuted among all DNS servers. • This distributed database is made up of Zone Files.

  18. How does DNS work? • In Windows Server – DNS services are turned on and you can see the DNS Console with the zone files. 

  19. How does DNS work? Each of the lines on the right is called a record.

  20. How does DNS work? You can add a new record by right clicking in the Zone File and choosing New Host(A) and this will display

  21. How does DNS work? DNS Levels At the top of the levels are the Root Servers - Root servers are designated with a "." The next level down are the Top Level Domain (TLD) servers - these are .com, .net, .org, .edu, .us, .au The next level down are the Domain Servers – like Google, Apple, Yahoo

  22. How does DNS work? DNS Levels Important to remember that: the Root servers know where the TLD servers are and the TLD servers know where the Domain servers are

  23. How does DNS work? FQDN (Fully Qualified Domain Names) These are read from right to left and should really start with a "." www.google.com. mail.bigpond.com. mail.iinet.net.au. www.illawarra.tafensw.edu.au.

  24. How does DNS work? • Example

  25. How does DNS work? Example A workstation wants to go to www.google.com The workstation asks its local DNS server for the IP address. The DNS Server looks in its Zone files and sees it doesn't have www.google.com. The local DNS Server goes straight to the top DNS level, i.e., a Root Server and says have you got the IP Address for www.google.com? The root server knows nothing about www.google but does know where the .COM servers are. It will send the IP address of the .com (TLD server) back to the local DNS server.

  26. How does DNS work? Example cont. Then the local DNS server asks the .Com server where the www.google server is (a Domain server). Since .com knows where all the Domain servers are it will send the IP address of google.com back to the local DNS server. The local DNS server will then ask the Domain server at google.com what is the address of WWW at Google. The Domain server at Google will look in its zone records, find the wwwentry and the IP address and send it to the local DNS server. The DNS server will give the IP address for www.google.com to the Workstation. The Workstation uses TCPIP to communicate with the Google web server.

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