DNS Name resolution

The parts of a DNS

.(dot) domain Top level domain fully qualified domain name additional domains host name records dynamic DNS (DDNS)

You need to enable hosts on your network to find the IP address of logical names such as srv1.myserver.com. Which device would you use? IDS Bandwidth shaper IPS DNS server Load balancer

DNS server Use a DNS server to provide host-name-to-IP-address resolution.

.(dot) domain

The . (dot) domain, or root domain, denotes a fully qualified, unambiguous domain name.

The Domain Name System DNS is a

hierarchical distributed database that maps logical host names to IP addresses.

Root DNS servers hold

information for the root zone (.)

host name

www

On small networks, you could configure a HOST file with several enteries to provide limited name resolution services, however,

you would have to copy the HOSTS files to each client. Only suitable for testign purposes

Dynamic DNS (DDNS)

A protocol that enables DNS servers to get automatic updates of IP addresses of computers in their forward lookup zones, mainly by talking to the local DHCP server.

Additional Domains

Additional domains are second-level domains with names registered to an individual or organization for use on the internet. These names are based on an appropriate top-level domain, depending on the type of organization or geographic location where a name is used. Yahoo.com and microsoft.com are examples of additional domains in your DNS structure.

DNS Records

Address Mapping records. Specifies IP address (IPv4) for given host. A records are used for conversion of domain names to corresponding addresses.

Authoritative Server

An authoritative server is a DNS server that has a complete copy of all the records for a particular domain.

You want to implement a protocol on your network that allows computers to find the IP address of a host from a logical name. Which protocol should you implement? DHCP Telnet DNS ARP

DNS

Which of the following services automatically creates and deletes host records when an IP address lease is created or released? Dynamic DNS Forward lookup DHCP Relay Dynamic NAT

Dynamic DNS

How do servers hold the portions of the data

Each division of the database is held in a zone database file Zones typically contain one or more domains DNS servers hold zone files and process name resolution requests from client systems.

The DNS record type MX function is to

Identifies servers that can be used to deliver mail

top-level domain (TLD)

Identifies the type of organization associated with the domain.

The DNS record type A function is to

Points a host name to an IPv4 address

The DNS record type AAAA function is to

Points a host name to an IPv6 address

The DNS record type PTR function is to

Points an IP address to a host name

The DNS record type CNAME function is to

Provides alternate names to hosts that already have a host record

fully qualified domain name (FQDN)

The complete domain name of an Internet computer, such as www.CIWcertified.com. The FQDN includes the host name and all domain names separated by periods. The final period (which is for the root domain) is often omitted and only implied.

Describe the steps of the Recursion process

The host looks in its local cache to see if it has recently resolved the host name. If the information is not in the cache, it checks the Hosts file. The Hosts file is a static text file that contains host-name-to-IP address mappings. If the IP address is not found, the host contacts its preferred DNS server. If the preferred DNS server can't be contacted, the host continues contacting additional DNS servers until one responds. The host sends the name information to the DNS server. The DNS server checks its cache and Hosts file. If the information is not found, the DNS server checks any zone files that it holds for the requested name. If the DNS server can't find the name in its zones, it forwards the request to a root zone name server. This server returns the IP address of a DNS server that has information for the corresponding top-level domain (such as .com). The first DNS server requests the information from the top-level domain server. The server returns the address of a DNS server with the information for the next highest domain. This process continues until a DNS server is contacted that holds the necessary information. The DNS server places the information in its cache and returns the IP address to the client host. The client host also places the information in its cache and uses the IP address to contact the desired destination device.

If dynamic DNS is being used, which of the following events will cause a dynamic update of the host records? (Select two.) The browser cache on a workstation is cleared. The ipconfig /registerdns command is entered on a workstation. A CNAME record is added to the DNS server. An MX record is added to the DNS server. The DHCP server renews an IP address lease.

The ipconfig /registerdns command is entered on a workstation. The DHCP server renews an IP address lease. Dynamic DNS (DDNS) enables clients or the DHCP server to update records in the zone database automatically. Dynamic updates occur when: A network host's IP address is added, released, or changed. The DHCP server changes or renews an IP address lease. The client's DNS information is manually changed using the ipconfig /registerdns command. Clearing a browser's cache has no effect on DNS records. Because MX records and CNAME records need to be manually added and created, they have no effect on DDNS.

Recursion process

When you use the host name of a computer, recursion is used to find the IP address

On the client, you can configure a list of DNS suffices you want to append to unqualified DNS names submitted by clients for resolution as follows:

configure a single DNS suffix for clients using a DHCP option on the DHCP server Configure multiple suffixes by adding then to the client manually

Root servers answer

name resolution requests by supplying the address of the corresponding top-level DNS server

DNS is a distributed database becuase

no one server holds all the DNS information, instead, multiple sercers hold portions of the data

A forward lookup finds

the IP address for a given host name

Reverse look up finds

the host name from a given IP address