INM 4010 Wide Area Networking with TCPIP Spring Semester 2000 Class 19

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INM 4010Wide Area Networking with TCP/IP Spring
Semester 2000Class 19
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DNS

• Domain Name System
• MS DNS integrates WINS.
• Hierarchical naming system( Composed of computer
  name and domain name).
• Uses UDP port 53.

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DHCP

• Dynamic Host Configuration Protocol
• A protocol for assigning dynamic IP addresses to
  devices on a network.
• With dynamic addressing, a device can have a
  different IP address every time it connects to
  the network.
• DHCP also supports a mix of static and dynamic IP
  addresses.

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Capabilities (DHCP/DNS)

• Utilizing DHCP, your clients automatically
  receive dynamic IP addresses and TCP/IP
  configuration information.
• Thus you can centrally administer IP assignments,
  provide support for roaming, clean up IP
  allocation by automatically returning unused IP
  addresses to the available pool for reuse, and
  have all the other benefits of DHCP.

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II

• Utilizing WINS, machines automatically register
  their NetBIOS computer name and IP address, every
  time they start up.
• If the computer moves between subnets, this
  information is automatically updated as well.

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III

• Utilizing DNS, your clients can find any
  nonWINS-aware resources through the static
  mappings maintained in the configuration files.
• This also works in reverse. Any nonWINS-aware
  client that uses DNS to resolve names and has a
  static mapping to your DNS service can locate a
  WINS client, even if the IP address is
  dynamically assigned with DHCP.

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Note on Server Selection

• If providing name resolution for many clients,
  should be dedicated and not a PDC.

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Terminology

• Domain
• Zone
• Host
• Reverse Lookup

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Domain

• All or part of a hierarchical name space. For
  example, com is the root or top-level domain for
  all commercial subdomains, such as microsoft.com.
  
• You can nest subdomains. For example, you can
  have west as a domain within abc.com, called
  west.abc.com.

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ZONE

• A specific kind of DNS configuration file.
• A zone file can include one or more domains, and
  provides the configuration information for those
  domains.
• For example, you can have a zone file for abc.com
  that includes information on west.abc.com.
  Alternatively, you can have one zone file on a
  server for abc.com and another zone file for
  west.abc.com on another server.
• In MS-DNS, zone files have file names with a .dns
  extension. For example, abc.com would have a
  corresponding zone file called abc.com.dns.

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Host

• A machine name with a corresponding IP address.
• When you create zones that represent a domain,
  you enter host information for machines that
  reside with that domain.
• For example, you might add a host named servera
  with IP address 192.168.200.1 to a zone file for
  abc.com. The Fully Qualified Domain Name (FQDN)
  for that server would then be servera.abc.com.

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Reverse Lookup

• When a client queries DNS (or WINS, for that
  matter), he is saying, "Tell me the IP address
  for hostname x."
• However, there are some applications (especially
  in the UNIX world) that say, "Tell me the
  hostname for this IP address 192.168.200.1.
• This is called a reverse lookup. MS-DNS supports
  the creation of reverse lookup maps for these
  purposes, though they are by no means required if
  you're not implementing services that require
  them.

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Name Servers

• Primary
• Secondary
• Caching

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Primary Name Servers

• The primary name server for a domain holds the
  master copy of the name database.
• This database contains the records for all hosts
  in the zone, as well as records for all the
  subdomains.

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Secondary Name Servers

• Secondary name servers holds a copy of the record
  database for the domain and subdomains.
• When changes are made to the domain, they are
  made to the primary DNS, and the updated database
  is replicated to all secondary DNS servers.

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Caching Name Servers

• Does not actually contain a copy of the record
  database.
• Configured with the address of either a primary
  or secondary DNS for a particular domain.
• When it receives a name query request, it asks
  the other name server to resolve the request. It
  then caches this information so that when it is
  asked for again, it will already cached.
• Effectively, the caching name server holds the
  all the frequently visited locations, and the
  size of its cached database will grow with time
  and use.

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Caching Only Server/IP Forwarder

• Gets results from upstream DNS server and caches
  the DNS entry.
• Does not host any zones.

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DNS Manager

• Your interface to managing the DNS Service is the
  DNS Manager in Administrative Tools program
  group.
• You must have administrative privileges to use
  this program. With the DNS Manager, you can do
  everything but stop or start the DNS Service.
• To stop or start the service, use the Control
  Panel Services applet and specify the Microsoft
  DNS Server as the service to control

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NSLOOKUP

• Enables you to examine the entries in zone files.
• DNS Manager is the Windows interface used to
  modify zone files.
• NSLOOKUP -options . . . Computer IP address.
  server

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Zones

• The administrative unit in the DNS
• Represents a subtree of the DNS, such as
  xyzcorp.com.
• Distributed in nature

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Default Records for a Domain

• By default, two records are created in the
  domain, an NS entry and an SOA entry.

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A RECORD

• Record type for new hosts.

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CNAME

• Canonical Name Record.
• Used to create Aliases.
• A record used to register the real host name.
• SOA Record contains Start of Authority
  Information.
• PTR Record exists only in Reverse Lookup Zones.
• MX Record contains Preference entry and the
  mail server name.

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NS SOA

• The NS record (Name Server) - specifies the
  selected machine as a name server in the domain.
• SOA record (Start of Authority) - details the
  name server that is the best source of
  authoritative information for the zone, as well
  as the e-mail address of a contact responsible
  for the domain

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MX Record

• A DNS server includes e-mail name resolution by
  supporting the MX record type, which associates
  an e-mail address with a hostname.
• Record type for mail exchanger for the domain.

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HINFO

• Host Information File

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Cache.DNS

• Name of file used to locate a higher DNS server
  on the Internet.
• \winnt\system32\dns\cache.dns

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Root Servers

• A.ROOT-SERVERS.NET
• 198.41.0.4 (Net-Sol)
• B.ROOT-SERVERS.NET
• 128.9.0.107 (Net-Sol)
• M.ROOT-SERVERS.NET (APNIC)
• 202.12.27.33

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Host Name Resolution

• Resolve Host Name to an IP Address.

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HOSTS

• ASCII text file
• Maps local and remote host names and Aliases to
  IP addresses.
• \systemroot\System32\Drivers\etc
• 255 characters per entry
• Unlimited number of entries.
• File read from top to bottom.
• Can contain aliases
• indicates comments.

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Resolution Process

• Local Host Name
• HOSTS File
• DNS
• WINS
• Broadcast
• LMHOSTS

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WINS resolution.

• The NT DNS server will only attempt to use WINS
  for resolution if it cannot find a matching
  hostname anywhere in its database.

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UNIX DNS

• Remember UNIX DNS servers cannot be secondary
  servers to WNT DNS servers that also handle WINS
  resolution.

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Folders

• Samples
• Backup

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BIND

• Controls the startup behavior of the DNS server.
• Includes information on the default directory
  where the configuration files reside, the cache
  filename, the domain name the DNS server will
  service, and the domain name for secondary DNS
  servers.

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BIND II

• CACHE This file contains information for
  Internet connectivity.
• PLACE.DOM This file contains information on
  hostnames in the domain. It also includes
  references to reverse lookup filenames and WINS
  servers.

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BIND III

• ARPA-.REV
• These files (there should be one per subnet)
  include information to resolve an IP address to a
  hostname.

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TLD

• Top Level Domain
• InterNIC.
• .COM, .EDU, .ORG, .NET, .GOV, .MIL
• Two-letter country codes.

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FQDN

• Fully Qualified Domain Name

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Reverse Lookup Zone

• Use network portion of the IP address.

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Any Questions?

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See you Thursday!