70-410 Lesson 12: DNS

resource record

In the Domain Name System, a unit of information that can contain host names, IP addresses, and other data.

zone

In the Domain Name System, an administrative entity created on a DNS server to represent a discrete portion of the DNS namespace.

reverse name resolution

In the Domain Name System, the process by which a server converts an IP address into a DNS name.

zone transfer

In the Domain Name System, the process by which the server hosting the primary zone copies the primary master zone database file to the secondary zone so that their resource records are identical.

c. contoso

In the fully qualified domain name www.sales.contoso.com, which of the following is the second-level domain? a. www b. sales c. contoso d. com

b. relay agents

Which of the following is not one of the elements of the Domain Name System (DNS)? a. resolvers b. relay agents c. name servers d. name space

a. 88.143.75.10.in-addr.arpa

Which of the following would be the correct FQDN for a resource record in a reverse lookup zone, if the computer's IP address is 10.75.143.88? a. 88.143.75.10.in-addr.arpa b. 10.75.143.88. in-addr.arpa c. in-addr.arpa.88.143.75.10 d. arpa.in-addr. 10.75.143.88

d. AAAA record

The IPv6 DNS host record is referred to as a(n): a. A record b. AA record c. AAA record d. AAAA record

a. Zone transfer

Data from a primary zone is transmitted to secondary zones using the following: a. Zone transfer b. Zone transmission c. DNS Zone d. Active Directory replication

All DNS server implementations are preconfigured with the IP addresses of the root name servers. Explanation: All DNS server implementations are preconfigured with the IP addresses of the root name servers, because these servers are the ultimate source for all DNS information.

How do DNS servers know how to find the DNS root name servers?

negative caching

The ability of a DNS server to retain information about names that do not exist in a domain

global domain

The com, org, and net domains that organizations anywhere in the world may use in order to register second-level domains.

Root servers Explanation: At the top of the DNS hierarchy are the root name servers. The root name servers are the highest-level DNS servers in the entire namespace, and they maintain information about the top-level domains. All DNS server implementations are preconfigured with the IP addresses of the root name servers, because these servers are the ultimate source for all DNS information.

What are the servers at the top of the DNS hierarchy called?

b. In the Server Manager window, click Tools > DNS. The DNS Manager console appears. e. Right-click the server node and, from the context menu, select Properties. The server's Properties sheet appears. a. Click the Forwarders tab. Click Edit. The Edit Forwarders dialog box appears. c. Type the name or address of the DNS server you want to function as a forwarder and press Enter. The system validates the name or address by connecting to the DNS server. d. Click OK to close the Edit Forwarders dialog box and add the servers to the Forwarders tab. Click OK to close the server's Properties sheet. Close the DNS Manager console. Explanation: To configure forwarders on a Windows Server 2012 R2 DNS server, right-click the server node, open the Properties sheet, and click the Forwarders tab. On this tab, you can add the names and addresses of the servers that you want your server to use as forwarders.

1. Order the steps to configure a DNS forwarder. a. Click the Forwarders tab. Click Edit. The Edit Forwarders dialog box appears. b. In the Server Manager window, click Tools > DNS. The DNS Manager console appears. c. Type the name or address of the DNS server you want to function as a forwarder and press Enter. The system validates the name or address by connecting to the DNS server. d. Click OK to close the Edit Forwarders dialog box and add the servers to the Forwarders tab. Click OK to close the server's Properties sheet. Close the DNS Manager console. e. Right-click the server node and, from the context menu, select Properties. The server's Properties sheet appears.

Time To Live (TTL) specified by each DNS server's administrator Explanation: The amount of time that DNS data remains cached on a server is called its Time To Live (TTL). Unlike most data caches, the TTL is not specified by the administrator of the server where the cache is stored. Instead, the administrators of each authoritative DNS server specify how long the data for the resource records in their domains or zones should be retained in the servers where it is cached.

A DNS server receives updated information. Other DNS servers have outdated information cached. What determines the amount of time that the old DNS data remains cached on a server and an update might occur?

a. Authoritative answer

A DNS server that hosts a primary or secondary zone containing a particular record can issue the following response to a query for that record: a. Authoritative answer b. Non-authoritative answer c. Referral answer d. Non-referral answer

caching-only server

A Domain Name System server that has the ability to process incoming queries from resolvers and send its own queries to other DNS servers on the Internet, but which is not the authoritative source for any domain and hosts no resource records of its own.

forwarder

A Domain Name System server that is configured to send the name resolution requests it receives from clients to another DNS server, specified by an administrator, using recursive, not iterative, queries.

domain

A set of network resources available for a group of users who can authenticate to the network to gain access to those resources.

country-code top level domain (ccTLD)

A top-level domain code using two letters to represent a particular country.

generic top-level domain (gTLD)

A top-level domain name referring to specific type of resource, as designated by ICANN.

The search begins at the top of the namespace hierarchy with the root name servers. It continues down the levels until it reaches the authoritative server for the domain in which the name is located. Explanation: At the top of the DNS hierarchy are the root name servers. The root name servers are the highest-level DNS servers in the entire namespace, and they maintain information about the top-level domains. All DNS server implementations are preconfigured with the IP addresses of the root name servers, because these servers are the ultimate source for all DNS information.

After a computer attempts to resolve a DNS name, how does the computer continue searching to find the authoritative source?

At the second-level domain level Explanation: No hosts exist in the root or top-level domains, except for the name servers themselves. For example, you do not see a DNS name consisting of only a host and a top-level domain, such as www.com. The root name servers do nothing but respond to millions of requests by sending out the addresses of the authoritative servers for the top-level domains, and the top-level domain servers do the same for the second-level domains.

At what level of the DNS hierarchy are actual hosts, apart from the root servers?

.com, .net, .org Explanation: The .edu, .gov, and .mil domains are reserved for use by certified organizations, but the .com, .org, and .net domains are called global domains, because organizations anywhere in the world can register second-level domains within them.

Concerning DNS domain hierarchy, what are examples of global top-level domains?

When a DNS server receives information about a non-existent host Explanation: Negative caching occurs when a DNS server retains information about names that do not exist in a domain. If, for example, a client sends a query to its DNS server containing a name in which the second-level domain does not exist, the top-level domain server will return a reply containing an error message to that effect. The client's DNS server will then retain the error message information in its cache. The next time a client requests a name in that domain, the DNS server will be able to respond immediately with its own error message, without consulting the top-level domain.

Concerning DNS, what is negative caching?

Caching-only servers are DNS servers that clients use to resolve names, but which are not the authoritative source for any domain. Explanation: In DNS terminology, a caching-only server is a DNS server that clients use to resolve names, but which is not the authoritative source for any domain.

How does a caching-only server differ from a normal DNS server?

Right-click the zone, open the Properties sheet, and click the Start Of Authority (SOA) tab. On this tab, you can modify the TTL for this record Explanation: To modify the TTL value for a zone on a Windows Server 2012 R2 DNS server, right-click the zone, open the Properties sheet, and click the Start Of Authority (SOA) tab. On this tab, you can modify the TTL for this record setting from its default value of one hour

How does an administrator change the TTL setting for a zone on a Windows Server 2012 R2 DNS server?

iterative query

In Domain Name System, a name resolution request in which the DNS server immediately responds with the best information it possesses at the time. Compare with recursive query.

recursive query

In Domain Name System, a name resolution request in which the DNS server takes full responsibility for resolving the name. If the server has no information about the name, it sends referrals to other DNS servers until it obtains the information it needs. Compare with iterative query.

fully qualified domain name (FQDN)

In Domain Name System, the complete DNS name for a particular computer, consisting at minimum of a host name, a second-level domain name, and a top-level domain name, written in that order and separated by periods.

host table

In TCP/IP, a list of host names and their equivalent IP addresses, used for name resolution in the early days of the Internet.

host

In TCP/IP, the network interface inside a computer or other device on a network.

resolver

In the Domain Name System, a client program that generates DNS queries and sends them to a DNS server for fulfillment.

e. In the Server Manager window, click Tools > DNS. The DNS Manager console appears. b. Expand the server node and select the Forward Lookup Zones folder. c. Right-click the Forward Lookup Zones folder and, from the context menu, select New Zone. The New Zone Wizard appears. Click Next to bypass the Welcome page. The Zone Type page appears. d. Leave the Primary Zone option and the Store The Zone In Active Directory (Available Only If DNS Server Is A Domain Controller) check box selected and click Next. The Active Directory Zone Replication Scope page appears. Click Next. The Zone Name page appears. a. Specify the name you want to assign to the zone in the Zone Name text box and click Next. The Dynamic Update page appears. f. Select one of the following options: Allow only secure dynamic updates, Allow both nonsecure and secure dynamic updates, or Do not allow dynamic updates. Click Finish. Close the DNS Manager console. Explanation: A zone is an administrative entity you create on a DNS server to represent a discrete portion of the DNS namespace. After you run the DNS server service on a computer that is an AD DS domain controller and you select the Store The Zone In Active Directory (Available Only If DNS Server Is A Domain Controller) check box while creating a zone in the New Zone Wizard, the server does not create a zone database file. Instead, the server stores the DNS resource records for the zone in the AD DS database.

Order the steps to create an Active Directory zone. a. Specify the name you want to assign to the zone in the Zone Name text box and click Next. The Dynamic Update page appears. b. Expand the server node and select the Forward Lookup Zones folder. c. Right-click the Forward Lookup Zones folder and, from the context menu, select New Zone. The New Zone Wizard appears. Click Next to bypass the Welcome page. The Zone Type page appears. d. Leave the Primary Zone option and the Store The Zone In Active Directory (Available Only If DNS Server Is A Domain Controller) check box selected and click Next. The Active Directory Zone Replication Scope page appears. Click Next. The Zone Name page appears. e. In the Server Manager window, click Tools > DNS. The DNS Manager console appears. f. Select one of the following options: Allow only secure dynamic updates, Allow both nonsecure and secure dynamic updates, or Do not allow dynamic updates. Click Finish. Close the DNS Manager console.

Maintaining that domain's resource records Explanation: The authoritative source for any domain is the DNS server (or servers) responsible for maintaining that domain's resource records. Each level of the DNS domain hierarchy has name servers responsible for the individual domains at that level.

Regarding DNS servers, what is the authoritative source for any domain responsible for?

hierarchical; periods Explanation: The domain name part of a DNS name is hierarchical and consists of two or more words, separated by periods. The DNS namespace takes the form of a tree that, much like a file system, has its root at the top.

The domain name part of a DNS name is _______ and consists of two or more words, separated by ______.

d. Secure dynamic updates

The following feature is available only on Active Directory-integrated DNS zones: a. Dynamic updates b. Incremental zone transfers c. Reverse lookup zones d. Secure dynamic updates

root name servers

The highest-level DNS servers in the entire Domain Name System namespace, which maintain information about the top-level domains.

name resolution

The process by which a Domain Name System server or other mechanism converts a host name into an IP address.

referral

The process by which one Domain Name System server sends a name resolution request to another DNS server.

recursive query Explanation: DNS servers use iterative queries when communicating with each other. In most cases, it is improper to configure one DNS server to send a recursive query to another DNS server. For example, if DNS servers send iterative queries rather than recursive queries to the root name servers, the additional burden on the root name servers would be immense, and probably cause the entire Internet to grind to a halt.

The typical query one DNS server sends to a root name server is called a(n) _______.

c. Conditional forwarder

This DNS configuration item will forward DNS queries to different servers based on the domain name of the query. a. Iterative forwarder b. Recursive forwarder c. Conditional forwarder d. IPv6 forwarder

Caching-only server Explanation: In DNS terminology, a caching-only server is a DNS server that clients use to resolve names, but which is not the authoritative source for any domain.

What DNS server is never the authoritative source for a domain, but only serves to resolve names?

Authoritative source Explanation: The hierarchical nature of the DNS namespace makes it possible for any DNS server on the Internet to locate the authoritative source for any domain name, by using a minimum number of queries.

What DNS server is responsible for maintaining a particular domain's resource records?

Forwarder Explanation: The only time a DNS server sends iterative queries to another server is in the case of a special type of server called a forwarder, which is specifically configured to interact with other servers in this way.

What DNS server normally sends iterative queries to another DNS server?

Root name server Explanation: At the top of the DNS hierarchy are the root name servers. The root name servers are the highest-level DNS servers in the entire namespace, and they maintain information about the top-level domains.

What DNS server represents the top of the DNS hierarchy?

a. Avoid an excessive number of domain levels.

What are some best practices when creating internal DNS namespaces. a. Avoid an excessive number of domain levels. b. Keep domain names full and descriptive; avoid concise subdomains. c. Place less importance on a convention compared to spelling. d. Never abbreviate.

a. Avoid an excessive number of domain levels. Explanation: When selecting names for your internal domains, you should observe the following rules: keep domain names short, avoid an excessive number of domain levels, create a naming convention and stick to it, avoid obscure abbreviations, and avoid names that are difficult to spell.

What are some best practices when creating internal DNS namespaces? a. Avoid an excessive number of domain levels. b. Keep domain names full and descriptive; avoid concise subdomains. c. Place less importance on a convention compared to spelling. d. Never abbreviate.

c. Specifying a TTL that is too short can overburden root name and top-level domain servers with requests.

What are the dangerous consequences of a poorly chosen Time To Live (TTL)? a. Specifying a TTL that is too long can greatly increase traffic, especially to the root name and top-level domain servers. b. Specifying a TTL that is too long can delay referrals from being propagated. c. Specifying a TTL that is too short can overburden root name and top-level domain servers with requests. d. Specifying a TTL that is too short can cause incorrectly cached information to remain before changes get recorded.

b. All Internet applications working with host names must use DNS to resolve host names into IP address. Explanation: Although all Internet applications use DNS to resolve host names into IP addresses, this name resolution process is easiest to see when you use a web browser to access an Internet site.

What client applications utilize DNS to resolve host names into IP addresses? a. Client web browsers, or any application that uses HyperText Transfer Protocol (HTTP), use DNS to resolve host names into IP addresses. b. All Internet applications working with host names must use DNS to resolve host names into IP address. c. Any application on a system that has connectivity to the Internet uses DNS to resolve host names into IP addresses. d. DNS does not resolve host names into IP addresses.

b. All Internet applications working with host names must use DNS to resolve host names into IP addresses.

What client applications utilize Domain Name System (DNS) to resolve host names into IP addresses? a. Client web browsers, or any application that uses HyperText Transfer Protocol (HTTP) use DNS to resolve host names into IP addresses. b. All Internet applications working with host names must use DNS to resolve host names into IP addresses. c. Any application on a system that has connectivity to the Internet use DNS to resolve host names into IP addresses. d. DNS does not resolve host names into IP addresses.

Authoritative source Explanation: The authoritative source for any domain is the DNS server (or servers) responsible for maintaining the domain's resource records. Each level of the DNS domain hierarchy has name servers responsible for the individual domains at that level.

What do you call the source responsible for maintaining a domain's resource records?

Name caching saves time and network traffic during the second name resolution request for the same name.

What is the benefit of name caching?

63; 255 Explanation: The only limitations to the subdomains and hosts you can create in your second-level domain are as follows: Each individual domain name can be no more than 63 characters long. The total FQDN (including the trailing period) can be no more than 255 characters long. For the convenience of users and administrators, most domain names do not approach these limitations.

What is the character limit on individual domain names, and the limit on the Fully Qualified Domain Names (FQDNs)?

1 hour Explanation: The amount of time that DNS data remains cached on a server is called its Time To Live (TTL). Administrators can specify a TTL value based on the volatility of their server data. To modify the TTL value for a zone on a Windows Server 2012 R2 DNS server, right-click the zone, open the Properties sheet, and click the Start Of Authority (SOA) tab. On this tab, you can modify the TTL for this record setting from its default value of one hour.

What is the default TTL for a Windows Server 2012 R2 DNS server?

c. 255 characters

What is the maximum length for a fully qualified domain name, including the trailing period? a. 50 characters b. 63 characters c. 255 characters d. 255 characters for each individual domain name

b. Reducing the traffic and making efficient use of available bandwidth across the network perimeter

What is the primary benefit of a DNS forwarder? a. Exchanging iterative queries for recursive queries across the network perimeter b. Reducing the traffic and making efficient use of available bandwidth across the network perimeter c. Making the most of iterative queries to other DNS servers d. Reducing the burden on the Internet's root name servers

b. Reducing the traffic and making efficient use of available bandwidth across the network perimeter Explanation: On a network running several DNS servers, you might not want all the servers sending queries to other DNS servers on the Internet. If the network has a slow connection to the Internet, for example, several servers transmitting repeated queries might use too much of the available bandwidth. To prevent this, most DNS implementations enable you to configure one server to function as the forwarder for all Internet queries generated by the other servers on the network.

What is the primary benefit of a DNS forwarder? a. Exchanging iterative queries for recursive queries across the network perimeter b. Reducing the traffic and making efficient use of available bandwidth across the network perimeter c. Making the most of iterative queries to other DNS servers d. Reducing the burden on the Internet's root name servers

d. Name caching enables the second name resolution request for the same name to bypass the referral process. Explanation: Name caching enables the second name resolution request for the same name to bypass the referral process. A DNS server that receives requests from clients, for example, caches the addresses of the requested systems, as well as the addresses for authoritative servers of particular domains. The next time that a client requests the resolution of a previously resolved name, the server can respond immediately with the cached information.

What is the primary purpose of name caching? a. Name caching saves an extraordinary amount of time for the user. b. Name caching greatly reduces traffic on the company network. c. Name caching validates why you should deploy caching-only servers. d. Name caching enables the second name resolution request for the same name to bypass the referral process.

d. Name caching enables the second name resolution request for the same name to bypass the referral process.

What is the primary purpose of name caching? a. Name caching saves extraordinary amount of time for the user. b. Name caching greatly reduces traffic on the company network. c. Name caching validates why you should deploy caching-only servers. d. Name caching enables the second name resolution request for the same name to bypass the referral process.

TCP, port 53 Explanation: If the data to be transmitted does not fit in a single UDP datagram, as in the case of zone transfers, the two systems establish a standard TCP connection, also by using port 53 on both machines, and transmit the data by using as many segments as needed.

When a DNS server communicates a large zone transfer to another DNS server, what type of datagram is used, and over what port?

UDP; 53 Explanation: DNS name resolution transactions use User Datagram Protocol (UDP) datagrams on port 53 for servers and an ephemeral port number for clients. Communication between two servers uses port 53 on both machines.

When a DNS server communicates a name resolution query to another DNS server, what type of datagram is used, and over what port?

Less traffic crossing the network perimeter Explanation: In the DNS name resolution process, the client resolver and its DNS server exchange one query message and one reply. If the clients on your local network use the DNS servers on your ISP's network, then your Internet connection has to handle only these two messages. If, however, you install a DNS server on your local network, the recursive queries the server receives from clients cause it to send numerous iterative queries to various other DNS servers on the Internet. These multiple message exchanges must all pass over the Internet connection. When you have hundreds or thousands of clients using the DNS server, the amount of iterative query traffic the server generates can overburden your Internet connection or greatly increase its cost.

When using DNS for name resolution only, why should a company consider using DNS servers outside the network perimeter?

Internet Corporation for Assigned Names and Numbers (ICANN) Explanation: The complete list of registrars that are accredited by ICANN is available at http://www.icann.org/registrars/accredited-list.html. ICANN is also responsible for the ratification of new top-level domains.

Who is responsible for the ratification of new top-level domains?

To allow a DHCP server to request a DNS server to update or create a record. Explanation: When computers lease their IP addresses from DHCP servers, the possibility exists for a particular computer's address to change. However, a manually created DNS resource record still contains the old IP address, leading to name resolution errors. To address this problem, the DNS server included in Windows Server 2012 R2 is compliant with the RFC 2136 document, called Dynamic Updates in the Domain Name System (DNS UPDATE). The dynamic update standard enables a DNS server to modify resource records at the request of DHCP servers and clients. Therefore, after a DHCP server assigns an address to a client, it can also send the appropriate commands to the DNS server, enabling it to create or update the resource records for the client.

Why is the DNS service included in Windows Server 2012 R2 integrated with DHCP service?

subdomains of contoso.com Explanation: After you purchase the rights to a second-level domain, you can create as many hosts as you want in that domain, by creating new resource records on the authoritative servers. You can also create as many additional domain levels as you want.

You registered the domain name contoso.com. The FQDNs seattle.contoso.com and halifax.contoso.com are examples of different _____.

c. Client system sends a recursive query message with the web address to the DNS server as specified in the system's TCP/IP configuration. b. Client's DNS server checks records for authoritative source for the zone containing the web address. DNS server sends iterative query to a root server. Root server responds with referral to top-level domain server address. a. Client's DNS server, with the top-level domain server address, generates a new iterative query and sends it to the top-level domain server. The top-level domain server responds with a referral to the second-level domain server. d. Client's DNS generates another iterative query and transmits it to the second-level domain server. Assuming second-level server is authoritative server for the zone containing the web address, it consults its records to determine IP address of requested system, and then messages back to the client's DNS server. e. Client's DNS receives reply from the authoritative server and transmits the IP address back to the client. The client's web browser now knows the IP address of the web server. Explanation: From the client's perspective, the procedure that occurs during these few seconds consists of the application sending a query message to its designated DNS server that contains the name to be resolved. The server replies with a message containing the IP address corresponding to that name. By using the supplied address, the application can transmit a message to the intended destination.

You type a web address in your web browser. Order the steps, which describe the Internet name resolution process for the web address. a. Client's DNS server, with the top-level domain server address, generates a new iterative query and sends it to the top-level domain server. The top-level domain server responds with a referral to the second-level domain server. b. Client's DNS server checks records for authoritative source for the zone containing the web address. DNS server sends iterative query to a root server. Root server responds with referral to top-level domain server address. c. Client system sends a recursive query message with the web address to the DNS server as specified in the system's TCP/IP configuration. d. Client's DNS generates another iterative query and transmits it to the second-level domain server. Assuming second-level server is authoritative server for the zone containing the web address, it consults its records to determine IP address of requested system, and then messages back to the client's DNS server. e. Client's DNS receives reply from the authoritative server and transmits the IP address back to the client. The client's web browser now knows the IP address of the web server.