Name Resolution and Domain Name System DNS

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Name Resolution and Domain Name System (DNS)

• Chapter Two

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NetBIOS to IP Address Resolution

• 16 character name
• 15 characters for name
• 16th function
• Looks in LMHOSTS
• NETBIOS to IP address static resolution
• Broadcast for name tcpip11 to be resolved
• Alternatively, contact WINS (Windows Internet
  Naming Service) server.
• Flat database, not hierarchical like DNS
• Computers register with WINS server

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Understanding DNS Name Resolution

• IP addresses - formed from four octets of numbers
  from 1 to 254
• 192.168.1.21 for example
• Name resolution is the process of converting
  these numerical IDs into names the average person
  can read and remember
• www.google.com for example

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Understanding DNS Name Resolution

• DNS created a hierarchical namespace
• Root (.)
• Top-level domain (.edu, .gov, .ca)
• Second-level domain (pbcc, google, military)
• Host (www, tcpip1, ftp)
• FQDNs www.pbcc.edu
• Relative distinguished names - www

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Domains
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Understanding DNS Name Resolution

• Dynamic DNS (DDNS) provides the means for
  updating a zones primary server automatically
• Will only work with Windows 2000/XP clients

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Understanding DNS Name Resolution

• Forward lookup query - standard method of name
  resolution in DNS
• Client sends a query to its primary DNS server,
  which in turn forward the request (if necessary)
  until the name is fully resolved
• A records

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Understanding DNS Name Resolution

• Sites are then cached on the primary DNS server,
  to avoid unnecessary traffic
• Reverse lookup queries can be used in
  troubleshooting, or for security purposes
• PTR records

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Operation of DNS

• Walk the tree
• Progressive query the DNS database structured
  from the root (.) to top level (com) to second
  level (google) to subdomain (business) to www.

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Understanding the Different Types of Name Servers

• Primary DNS servers
• Secondary DNS servers
• Caching-only name servers
• Forwarding DNS servers

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Primary DNS Servers

• The primary DNS server is the authoritative
  server for the zone
• Any changes to the DNS domain must be made here
• Read/Write Copy of DNS Database

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Secondary DNS Servers

• Serves as a backup for the primary DNS server
  (failover)
• Can also be used for load balancing
• Read Only Copy of DNS Database

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Caching-only Name Servers

• Functions only to cache name resolution queries
• Advantage is that network traffic is
  significantly reduced

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Forwarding Servers
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Configuring and Managing DNS Zones

• A zone is a partitioned portion of the overall
  namespace
• Separate administration.
• Which DNS server ultimately has authority for
  that domains records.

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Understanding Zone Transfers

• Zone transfer - process by which changes on the
  primary DNS server are replicated to all
  secondary servers in the zone
• Full zone transfer
• Incremental transfer
• DNS Notify

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Full Zone Transfer

• Entire zone database file is replicated between
  primary and secondary servers
• The secondary servers initiate

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Incremental Transfer

• Replicates only that portion of the database that
  has been changed
• Primary server keeps track of the changes through
  the use of a version history

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DNS Notify

• An update to incremental transfer process
• Primary server notifies secondary servers
  whenever an update is made to the database
• Helps the zone database remain consistent
  throughout the enterprise

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Installing DNS

• Before installing, you must configure a static IP
  address

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Installing DNS
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DNS Installation

• Install DNS

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Configuring DNS for Active Directory

• Consider the following when configuring DNS
• Root servers
• Forward lookup zones
• Reverse lookup zones
• Resource records
• Dynamic DNS

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Configuring DNS for Active Directory

• Root servers - create a root server only if your
  network is not connected to the Internet. Using
  this configuration, the root server will be
  authoritative for any namespace you create.

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Configuring DNS for Active Directory

• Forward lookup zones
• Active Directory-integrated
• Standard Primary
• Standard Secondary

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Configuring DNS for Active Directory

• Active Directory-integrated zone - through AD,
  all DCs are replicated a fully writeable copy of
  the zone database
• This provides a higher level of fault tolerance
  and flexibility

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Configuring DNS for Active Directory

• Standard Primary zone - standard zone
  configuration, must be used with non-Windows 2000
  servers
• Standard Secondary zone - draws its zone
  information from one or more primary servers

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Configuring DNS for Active Directory

• Standard Secondary zone - specify the name or
  names of the zones from which to receive zone
  information

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Configuring DNS for Active Directory

• Reverse Lookup Zones - create these to enable
  tools such as nslookup. Use the configurations
  available for forward lookup zones.

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Configuring DNS for Active Directory

• Resource records are basic units of information
  in DNS.
• Structure of files
• Owner
• TTL
• Class
• Type
• RDATA

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Configuring DNS for Active Directory
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Configuring DNS for Active Directory

• Commonly used resource records
• Start of Authority (SOA)
• Name Server (NS)
• Address (A)
• Pointer (PTR)
• Mail Exchanger (MX)
• Service (SRV)
• Canonical Name (CNAME)

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Configuring DNS for Active Directory

• Dynamic DNS (DDNS) - automatically adds resource
  records when a new Windows 2000 client boots up.

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Monitoring and Troubleshooting DNS for AD
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Monitoring and Troubleshooting DNS for AD
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Monitoring and Troubleshooting DNS for AD

• DNS Logging is a troubleshooting tool.

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Monitoring and Troubleshooting DNS for AD

• Name resolution is first attempted through cache.
• Clear local names that have been cached.
• ipconfig /flushdns

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Troubleshooting DNS for AD

• Use nslookup for troubleshooting and as a
  security tool
• server tcpip1.central.pbcc.edu connect to DNS
  server you are testing
• tcpip4.north.pbcc.edu attempt to resolve a name
  to ip address
• ping FQDN ping tcpip4.north.pbcc.edu