When we enter a particular site we register www.bartosha.com
Whoever is responsible for translating this name into an IP address is the provider’s DNS server, if the provider’s DNS does not know then he continues the request to another DNS server in the world since he knows and then redirects the answer back to us. That way, we can always get an answer, no matter where the site is.
When we created the domain, we installed DNS in our domain and named Resolver – a client computer that generates a DNS query and sends it to the configured server, the query includes a request to decrypt some name or to locate a particular service.
The DNS server is the server configured on its network card.
What does it look like on the net?
• The request goes to the root (dot) servers
• The point identifies the first stage of the domain name (1st lvl Domain Name), for example: .com
• Then the point goes through the second stage of the domain name (2st lvl Domain Name) for example: .co.il / com
• Once the correct server is identified, it is saved in Root Hints
• The client’s DNS server receives the correct routing of the DNS server it was looking for
• The engagement is in progress from now on
This is actually a very long connection, so how do we actually get to sites so quickly:
The answer is Caching:
• We previously found the bartosha.co.il site using DNS servers
• We are currently looking for the mail.bartosha.com website
• Instead of going all the way again, we can use the cache shortcut to search bartosha.com
Recursive Query – The DNS can’t find the information the client is requesting, it addresses the root servers with the Iterative Query request and they return the best information they know
Forwarder – Responsible for all of our DNS service
Conditional Forwarder – Responsible only for specific services that are configured for it
DNS servers
CRC Order Conversion Order:
- Client Resolver Cache – An internal table on a computer that has the values of computers that you contacted. Each address has an “expiration time” meaning that after a certain amount of time without communication from the computer, the address will be deleted from the cache.
A command to display the above cache is Ipconfig / DisplayDNS - Hosts file – editable. Each value in this file will appear in the above table as fixed (no expiration time).
Hosts Default Path – C: win \ system32 \ drivers \ … - DNS – a name conversion server, converts numeric addresses (for example 192.168.2.1) to name network addresses for example: www.bartosha.com and vice versa
- WINS – Old DNS server (for NetBIOS names)
- NetBIOS like CRC but only works for NetBIOS names
- Lmhosts – Names file only for NetBIOS names
- Broadcast If you have not found your computer by now, the computer will send a “shout” to the entire network to find the computer, the shout goes to 255.255.255.255 The address is a reserved address, the address is the address of all computers on the network because everyone “hears” when transmitting on 255.255.255.255
Introduction to DNS:
Important Terms: Root Hints
A file where the “dot” servers are listed means the global DNS servers.
The role of the DNS server is to convert numeric addresses to Semitic addresses, and vice versa.
For each network that the DNS is serving, it has a Zone.
Zone – Distribution of domains to a domain that can retrieve information from another DNS server in the world /
The DNS holds information in each zone about the computers by records called RR (Resource Records).
Types of Zones:
Primary – This is a zone for reading and writing – in any forest there can be only one of these types.
Secondary – This is a read-only zone (e.g., another non-DNS server)
Stub – actually a kind of record that redirects to primary DNS requests (e.g., secondary branch DNS that addresses the primary DNS server in the organization)
FLZ – Forward Lookup Zone = Used to convert from an IP address to a numeric address (IP)
RLZ – Reverse Lookup Zone = Used to convert from a numeric (IP) address to a name address
RR Record Types – Resource Records:
A-Convert away to IP
AAAA – Same goes for IPV6 protocol
CNAME – another name for the same computer (alias)
MX-Mail Service
NS – Various services
SRV – Any service that wants to advertise itself in DNS does so by the above record (shortening Service)
SOA – State Of Authority The first entry in the Zone that holds all of the Zone settings
PTR – Reverse conversion from IP address to Semitic address
Ways to see the Root Hints
Login to C: Windows / System32 / DNS / CacheDNS
Can be opened in Notepad
Explanation Aging and Scavenging:
When RR – Resource Records are created in DNS
They are in the field: Non-Refresh Interval
If they are not touched for 7 days, they will move to the Refresh Interval field
If it is 14 days (changeable) the record will become a “expired” or Stale entry
When we do Scavenging we actually delete the Stale records from the DNS server
About The Author
