1. Chapter 10 Configuring DNS
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam
Chapter 10
Configuring DNS
Chapter 10
Configuring DNS

2. Objectives Describe the structure of Domain Name System
Install and configure DNS
Configure DNS zones
Configure advanced DNS server settings
Monitor and troubleshoot DNS
Objectives
Describe the structure of Domain Name System
Install and configure DNS
Configure DNS zones
Configure advanced DNS server settings
Monitor and troubleshoot DNS
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

3. Introduction to Domain Name System
Domain Name System (DNS) is a distributed hierarchical database composed mainly of computer name and IP address pairs
Distributed means no single database contains all data and hierarchical means there’s no structure to how information is stored and accessed in the database
In order to resolve a name to an address, a DNS lookup will often require multiple queries to a hierarchy of DNS servers
Introduction to Domain Name System\
Domain Name System (DNS) is a distributed hierarchical database composed mainly of computer name and IP address pairs
Distributed means no single database contains all data and hierarchical means there’s no structure to how information is stored and accessed in the database
In order to resolve a name to an address, a DNS lookup will often require multiple queries to a hierarchy of DNS servers
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

4. The Structure of DNS
DNS can be described as an inverted tree structure
The entire DNS tree is called the DNS namespace
Each domain has one or more servers that are authoritative for the domain
Root servers keep a database of addresses of other DNS servers managing top-level domain names, called top-level domain (TLD) servers
The Structure of DNS
DNS can be described as an inverted tree structure
The entire DNS tree is called the DNS namespace
Each domain has one or more servers that are authoritative for the domain
Root servers keep a database of addresses of other DNS servers managing top-level domain names, called top-level domain (TLD) servers
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5. Figure 10-1 A partial view of the DNS naming hierarchy
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

6. The DNS Database
A zone is a grouping of DNS information that represents one or more domains and possibly sub-domains
Zones contain a variety of record types called resource records, which contain information about network resources
DNS records can be added and changed by:
Static updates - administrator enters DNS record information manually
Dynamic updates - referred to as Dynamic DNS (DDNS)
The DNS Database
A zone is a grouping of DNS information that represents one or more domains and possibly sub-domains
Zones contain a variety of record types called resource records, which contain information about network resources
DNS records can be added and changed by:
Static updates - administrator enters DNS record information manually
Dynamic updates - referred to as Dynamic DNS (DDNS)
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7. The DNS Lookup Process Two types of DNS lookup can be performed:
Iterative Query - a DNS server will respond with the best information it has to satisfy the query, or it may give a referral response
Recursive Query - a DNS server processes the query until it responds with an address that satisfies the query or with an “I don’t know message”
A typical DNS lookup made by a DNS client can involve both recursive and iterative queries
DNS clients maintain a text file that can contain static DNS entries and the file is stored in %systemroot%\System32\drivers\etc
The DNS Lookup Process
Two types of DNS lookup can be performed:
Iterative Query - a DNS server will respond with the best information it has to satisfy the query, or it may give a referral response
Recursive Query - a DNS server processes the query until it responds with an address that satisfies the query or with an “I don’t know message”
A typical DNS lookup made by a DNS client can involve both recursive and iterative queries
DNS clients maintain a text file that can contain static DNS entries and the file is stored in %systemroot%\System32\drivers\etc
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8. Figure 10-2 A DNS hierarchical lookup
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9. DNS Server Roles
DNS Servers can perform one or more of the following roles for a zone:
Authoritative server - holds a complete copy of a zone’s resource records
Forwarder - a DNS server to which other DNS servers send requests they can’t resolve themselves
Conditional forwarder - a DNS Server to which other DNS servers send requests targeted for a specific domain
Caching-only server - does not have zones and it’s job is to field DNS queries, do recursive lookups to root servers or send requests to forwarders, and then cache the results
DNS Server Roles
DNS Servers can perform one or more of the following roles for a zone:
Authoritative server - holds a complete copy of a zone’s resource records
Forwarder - a DNS server to which other DNS servers send requests they can’t resolve themselves
Conditional forwarder - a DNS Server to which other DNS servers send requests targeted for a specific domain
Caching-only server - does not have zones and it’s job is to field DNS queries, do recursive lookups to root servers or send requests to forwarders, and then cache the results
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10. Installing and Configuring DNS
A correctly configured and efficiently functioning DNS service is essential for a well-functioning network
When domain controllers replicate with one another and when trusts are created between domains in different forests, DNS is required to resolve names and services to IP addresses
Installing and Configuring DNS
A correctly configured and efficiently functioning DNS service is essential for a well-functioning network
When domain controllers replicate with one another and when trusts are created between domains in different forests, DNS is required to resolve names and services to IP addresses
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

11. Installing DNS
DNS installation begins by installing the DNS Server role with Server Manager or PowerShell
If the DNS server is intended to manage domain name services for Active Directory, DNS Server role should be installed on a domain controller
Windows automatically detects whether or not the server is configured as a domain controller, then integrates DNS zones with Active Directory
Installing DNS
DNS installation begins by installing the DNS Server role with Server Manager or PowerShell
If the DNS server is intended to manage domain name services for Active Directory, DNS Server role should be installed on a domain controller
Windows automatically detects whether or not the server is configured as a domain controller, then integrates DNS zones with Active Directory
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

12. Creating DNS Zones
You may need to create a zone manually in DNS Manager if you:
Don’t install DNS at the time you install Active Directory
Install DNS on a server that’s not a domain controller
Create a stub zone
Create a secondary zone for a primary zone
Create a primary or secondary zone for an Internet domain
Creating DNS Zones
You may need to create a zone manually in DNS Manager if you:
Don’t install DNS at the time you install Active Directory
Install DNS on a server that’s not a domain controller
Create a stub zone
Create a secondary zone for a primary zone
Create a primary or secondary zone for an Internet domain
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13. Forward and Reverse Lookup Zones
Before creating a zone, you must decide whether it’s a forward lookup zone or a reverse lookup zone:
Forward lookup zone (FLZ) – contains records that translate names to IP addresses, such as A, AAAA, and MX records
Reverse lookup zone (RLZ) – contains PTR records that map IP addresses to names and is named after the IP network address (IPv4 or IPv6) of the computers whose records it contains
Forward and Reverse Lookup Zones
Before creating a zone, you must decide whether it’s a forward lookup zone or a reverse lookup zone:
Forward lookup zone (FLZ) – contains records that translate names to IP addresses, such as A, AAAA, and MX records
Reverse lookup zone (RLZ) – contains PTR records that map IP addresses to names and is named after the IP network address (IPv4 or IPv6) of the computers whose records it contains
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14. Zone Type Three different types of zones:
Primary zone - contains a read/write master copy of all resource records for the zone; it is considered authoritative for the zone
Secondary zone - contains a read-only copy of all resource records for the zone; it is considered authoritative for the zone
Stub zone - contains a read-only copy of only the SOA and NS records for a zone and the necessary A records to resolve NS records; not authoritative
Zone Type
Three different types of zones:
Primary zone - contains a read/write master copy of all resource records for the zone; it is considered authoritative for the zone
Secondary zone - contains a read-only copy of all resource records for the zone; it is considered authoritative for the zone
Stub zone - contains a read-only copy of only the SOA and NS records for a zone and the necessary A records to resolve NS records; not authoritative
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15. Active Directory-Integrated Zones
Active Directory-Integrated zone - not a new zone type but it is a primary or stub zone with the DNS database stored in an Active Directory partition
The only valid zone type options are primary and stub zones
If you select a secondary zone, the option to store the zone in Active Directory is disabled
Active Directory-Integrated Zones
Active Directory-Integrated zone - not a new zone type but it is a primary or stub zone with the DNS database stored in an Active Directory partition
The only valid zone type options are primary and stub zones
If you select a secondary zone, the option to store the zone in Active Directory is disabled
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16. Standard Zones
Standard zone - a primary, secondary, or stub zone that isn’t Active Directory-integrated
Standard zones are stored in a text file called zone-name.dns, which is located in the %systemroot%\system32\dns folder
Mostly installed on stand-alone servers that need to provide name resolution services for network resources outside the domain
Or in networks that don’t use Active Directory, such as Linux or UNIX-based networks
Standard Zones
Standard zone - a primary, secondary, or stub zone that isn’t Active Directory-integrated
Standard zones are stored in a text file called zone-name.dns, which is located in the %systemroot%\system32\dns folder
Mostly installed on stand-alone servers that need to provide name resolution services for network resources outside the domain
Or in networks that don’t use Active Directory, such as Linux or UNIX-based networks
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17. Zone Replication
Zone replication - the transfer of zone changes from one DNS server to another
For a standard zone, zone replication is called “zone transfer”
Active Directory-integrated zones have the following advantages over a standard zone:
Automatic zone replication
Multimaster replication and update
Secure updates
Efficient replication
Zone Replication
Zone replication - the transfer of zone changes from one DNS server to another
For a standard zone, zone replication is called “zone transfer”
Active Directory-integrated zones have the following advantages over a standard zone:
Automatic zone replication
Multimaster replication and update
Secure updates
Efficient replication
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18. Active Directory Zone Replication Scope
After selecting the zone type and specifying the zone is to be stored in Active directory, you are asked to select the zone replication scope with one of these options:
To all DNS servers in this forest
To all DNS servers running on domain controllers in this domain
To all domain controllers in this domain (for Windows 2000 compatibility)
To all domain controllers specified in the scope of this directory partition
Active Directory Zone Replication Scope
After selecting the zone type and specifying the zone is to be stored in Active directory, you are asked to select the zone replication scope with one of these options:
To all DNS servers in this forest
To all DNS servers running on domain controllers in this domain
To all domain controllers in this domain (for Windows 2000 compatibility)
To all domain controllers specified in the scope of this directory partition
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19. Figure 10-6 Selecting a zone replication scope
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20. Zone Name The next step is to give the zone a name
For an FLZ, it’s the FQDN
For an RLZ, specify whether it’s an IPv4 or IPv6 zone
Then, enter the network ID portion of the zone
The zone name is created automatically by using the network ID’s octets in reverse order and appending “in-addr.arpa” to the name
Zone Name
The next step is to give the zone a name
For an FLZ, it’s the FQDN
For an RLZ, specify whether it’s an IPv4 or IPv6 zone
Then, enter the network ID portion of the zone
The zone name is created automatically by using the network ID’s octets in reverse order and appending “in-addr.arpa” to the name
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21. Dynamic Updates
The final step allows you to choose whether and how to use dynamic updates, which can be configured in one of three ways:
Allow only secure dynamic updates
Allow both nonsecure and secure dynamic updates
Do not allow dynamic updates
Dynamic updates enable DNS client computers to register and dynamically update their resource records with a DNS server whenever changes occur
Dynamic Updates
The final step allows you to choose whether and how to use dynamic updates, which can be configured in one of three ways:
Allow only secure dynamic updates
Allow both nonsecure and secure dynamic updates
Do not allow dynamic updates
Dynamic updates enable DNS client computers to register and dynamically update their resource records with a DNS server whenever changes occur
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22. Creating Resource Records in Zones
Resource records can be created dynamically or as static records
Dynamic records are created by the resource or with a DHCP server
Static records are created manually by an administrator or automatically by Windows
Creating Resource Records in Zones
Resource records can be created dynamically or as static records
Dynamic records are created by the resource or with a DHCP server
Static records are created manually by an administrator or automatically by Windows
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

23. Creating Dynamic DNS Records
Dynamic DNS records are created and updated by the resource or by the DHCP server when an IP address is leased or renewed
Each time a dynamic record is created or updated, a time-to-live (TTL) value and timestamp are added to the record
The TTL specifies how long the record should remain in the DNS database
If the record expires, it’s deleted from the database
Creating Dynamic DNS Records
Dynamic DNS records are created and updated by the resource or by the DHCP server when an IP address is leased or renewed
Each time a dynamic record is created or updated, a time-to-live (TTL) value and timestamp are added to the record
The TTL specifies how long the record should remain in the DNS database
If the record expires, it’s deleted from the database
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24. Creating Static DNS Records
Static DNS records do not expire and are created manually by an administrator
To create a static record in DNS Manager:
Right-click the zone and select the record type
In an FLZ, the most common type of record is a New Host record
Enter a name to create the FQDN automatically
If you select the “Create associated pointer (PTR) record” check box, a PTR record is created if a suitable RLZ exists for the IP address entered
Creating Static DNS Records
Static DNS records do not expire and are created manually by an administrator
To create a static record in DNS Manager:
Right-click the zone and select the record type
In an FLZ, the most common type of record is a New Host record
Enter a name to create the FQDN automatically
If you select the “Create associated pointer (PTR) record” check box, a PTR record is created if a suitable RLZ exists for the IP address entered
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25. Configuring DNS Zones Zones can be viewed and changed in DNS Manager
DNS Manager provides the following options:
Status
Type
Replication
Dynamic updates
Aging
Configuring DNS Zones
Zones can be viewed and changed in DNS Manager
DNS Manager provides the following options:
Status
Type
Replication
Dynamic updates
Aging
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

26. Start of Authority Records
SOA records are found in every zone and contain information that identifies the server primarily responsible for the zone as well as some operation properties for the zone
The SOA record contains the following information:
Serial number
Primary server
Responsible person
Refresh interval
Retry interval
Expires after
Minimum (default) TTL
Start of Authority Records
SOA records are found in every zone and contain information that identifies the server primarily responsible for the zone as well as some operation properties for the zone
The SOA record contains the following information:
Serial number
Primary server
Responsible person
Refresh interval
Retry interval
Expires after
Minimum (default) TTL
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27. Name Server Records
NS records specify FQDNs and IP addresses of authoritative servers for a zone
NS records are also used to refer DNS queries to a name server that has been delegated authority for a subdomain
Glue A records are A records containing a name server’s IP address, and are used to resolve NS record information
On Windows DNS servers, glue records are created automatically by a DNS lookup on the NS record’s FQDN
Name Server Records
NS records specify FQDNs and IP addresses of authoritative servers for a zone
NS records are also used to refer DNS queries to a name server that has been delegated authority for a subdomain
Glue A records are A records containing a name server’s IP address, and are used to resolve NS record information
On Windows DNS servers, glue records are created automatically by a DNS lookup on the NS record’s FQDN
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28. Using Stub Zones
Stub zones are a special type of zone that contain only an SOA record, one or more NS records, and the necessary glue A records to resolve NS records
Reasons for using stub zones:
Maintenance of zone delegation information
In lieu of conditional forwarders
Faster recursive queries
Distribution of zone information
Using Stub Zones
Stub zones are a special type of zone that contain only an SOA record, one or more NS records, and the necessary glue A records to resolve NS records
Reasons for using stub zones:
Maintenance of zone delegation information
In lieu of conditional forwarders
Faster recursive queries
Distribution of zone information
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29. Zone Transfers
A zone transfer copies all or part of a zone from one DNS server to another and occurs as a result of a second server requesting the transfer from another server
Zone transfers can be initiated in two ways:
Refresh interval
DNS notify
Zone transfers are configured in the Zone Transfers tab of a zone’s Properties dialog box, which has the following options:
Allow zone transfers
To any server
Only to servers listed on the Name Servers tab
Only to the following servers
Notify
Zone Transfers
A zone transfer copies all or part of a zone from one DNS server to another and occurs as a result of a second server requesting the transfer from another server
Zone transfers can be initiated in two ways:
Refresh interval
DNS notify
Zone transfers are configured in the Zone Transfers tab of a zone’s Properties dialog box, which has the following options:
Allow zone transfers
To any server
Only to servers listed on the Name Servers tab
Only to the following servers
Notify
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30. Incremental Zone Transfers
Two types of zone transfer:
Full zone transfers
Incremental zone transfers
Both master and slave DNS servers must support incremental zone transfers to use them
During the initiation of an incremental zone transfer, the serial number decides whether the slave or the master determines the differences between its current zone data and the zone data on the other server
Incremental Zone Transfers
Two types of zone transfer:
Full zone transfers
Incremental zone transfers
Both master and slave DNS servers must support incremental zone transfers to use them
During the initiation of an incremental zone transfer, the serial number decides whether the slave or the master determines the differences between its current zone data and the zone data on the other server
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31. Using the GlobalNames Zone
GlobalNames zone (GNZ) allows administrators to add single-label names to DNS, giving client computers the ability to resolve these names without including a DNS suffix in the query
Entries must be made manually
Can assist mobile users by dropping the need for remembering a resource’s FQDN
Using the GlobalNames Zone
GlobalNames zone (GNZ) allows administrators to add single-label names to DNS, giving client computers the ability to resolve these names without including a DNS suffix in the query
Entries must be made manually
Can assist mobile users by dropping the need for remembering a resource’s FQDN
Use the following Powershell cmdlet to enable GNZ:
Set -DnsServerGlobalNameZone -Enable $true
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

32. Advanced DNS Server Settings
DNS server settings to configure an optimal DNS environment:
Forwarders
Root hints
Round Robin
Recursion
Debug logging
Advanced DNS Server Settings
DNS server settings to configure an optimal DNS environment:
Forwarders
Root hints
Round Robin
Recursion
Debug logging
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

33. DNS Forwarders
Referring a DNS query to a forwarder can be more efficient under some situations:
When the DNS server address for the target domain is known
When only one DNS server in a network should make external queries
When a forest trust is created
When the target domain is external to the network and an external DNS server’s address is known
Conditional forwarding allows queries for particular domains to particular name servers and all other unresolved queries to a different server
DNS Forwarders
Referring a DNS query to a forwarder can be more efficient under some situations:
When the DNS server address for the target domain is known
When only one DNS server in a network should make external queries
When a forest trust is created
When the target domain is external to the network and an external DNS server’s address is known
Conditional forwarding allows queries for particular domains to particular name servers and all other unresolved queries to a different server
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

34. Configuring Traditional Forwarders
To configure a traditional forwarder, right click the server node in DNS Manager, click Properties, and click the Forwarders tab
If more than one server is specified, they are queried in the order in which they’re listed
Additional servers are only queried if the first server provides no response
No response from any forwarders triggers a normal recursive lookup process, starting with a root server
Configuring Traditional Forwarders
To configure a traditional forwarder, right click the server node in DNS Manager, click Properties, and click the Forwarders tab
If more than one server is specified, they are queried in the order in which they’re listed
Additional servers are only queried if the first server provides no response
No response from any forwarders triggers a normal recursive lookup process, starting with a root server
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35. Figure 10-15 Configuring traditional forwarders
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

36. Configuring Conditional Forwarders
Conditional forwarders are configured in the Conditional Forwarders node in DNS Manager
With forwarders and/or conditional forwarders configured, the DNS server attempts to resolve DNS queries in this order:
1. From locally stored zone resource records
2. From the DNS cache
3. From conditional forwarders
4. From traditional forwarders
5. Recursively by using root hints
Configuring Conditional Forwarders
Conditional forwarders are configured in the Conditional Forwarders node in DNS Manager
With forwarders and/or conditional forwarders configured, the DNS server attempts to resolve DNS queries in this order:
1. From locally stored zone resource records
2. From the DNS cache
3. From conditional forwarders
4. From traditional forwarders
5. Recursively by using root hints
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37. Root Hints
Root hints consist of a list of name servers preconfigured on Windows DNS servers that point to Internet root servers
These servers contain lists of name servers that are responsible for top-level domains
Root hints data comes from the Cache.dns file located in the %systemroot%\System32\DNS folder
Internal DNS servers can be configured as root servers if the network is isolated from the public Internet
Root Hints
Root hints consist of a list of name servers preconfigured on Windows DNS servers that point to Internet root servers
These servers contain lists of name servers that are responsible for top-level domains
Root hints data comes from the Cache.dns file located in the %systemroot%\System32\DNS folder
Internal DNS servers can be configured as root servers if the network is isolated from the public Internet
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

38. Round Robin
Load sharing can be configured among servers running mirrored services
Accomplished by creating multiple A records with the server’s name in the records, but with each entry configured with a different IP address
DNS will then respond to queries by sending all addresses associated with the server’s name, but will also vary their order
This process is called round robin because each IP address is placed first in the list an equal number of times
Round Robin
Load sharing can be configured among servers running mirrored services
Accomplished by creating multiple A records with the server’s name in the records, but with each entry configured with a different IP address
DNS will then respond to queries by sending all addresses associated with the server’s name, but will also vary their order
This process is called round robin because each IP address is placed first in the list an equal number of times
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39. Recursive Queries
Recursion is enabled on Windows DNS servers by default, but there are two ways to change this setting
First involves configuring forwarders
Second is the “Disable recursion (also disables forwarders)” option in the Advanced tab of the DNS server’s Properties dialog box
You might want to disable recursion when you have a public DNS server containing resource records for your publicly available servers
Recursive Queries
Recursion is enabled on Windows DNS servers by default, but there are two ways to change this setting
First involves configuring forwarders
Second is the “Disable recursion (also disables forwarders)” option in the Advanced tab of the DNS server’s Properties dialog box
You might want to disable recursion when you have a public DNS server containing resource records for your publicly available servers
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

40. Event and Debug Logging
When DNS is installed, a new event log is created to record informational, error, and warning events generated by the DNS server
Common events include zone serial number changes, zone transfer requests, and DNS server startup and shutdown events
Debug logging can be enabled in the server’s Properties dialog box
Debug logging records selected packets coming from and going to the DNS server in a text file
Event and Debug Logging
When DNS is installed, a new event log is created to record informational, error, and warning events generated by the DNS server
Common events include zone serial number changes, zone transfer requests, and DNS server startup and shutdown events
Debug logging can be enabled in the server’s Properties dialog box
Debug logging records selected packets coming from and going to the DNS server in a text file
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41. Figure 10-17 The Event Logging tab
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

42. Table 10-3 PowerShell cmdlets for DNS server settings
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

43. Monitoring and Troubleshooting DNS
To troubleshoot a DNS problem, you need to know that DNS is actually used for name resolution
After determining that DNS is part of the process, you can begin monitoring DNS
If the problem is performance related
Or, you can troubleshoot DNS queries and zone activities when there are query failures
Monitoring and Troubleshooting DNS
To troubleshoot a DNS problem, you need to know that DNS is actually used for name resolution
After determining that DNS is part of the process, you can begin monitoring DNS
If the problem is performance related
Or, you can troubleshoot DNS queries and zone activities when there are query failures
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

44. DNS Troubleshooting
Windows has several tools to administer, monitor, and troubleshoot DNS server operation, including:
DNS Manager
dcdiag /test:dns
dnscmd.exe
PowerShell
Event Viewer
dnslint
nslookup
ipconfig
Performance Monitor
Protocol analyzer
DNS Troubleshooting
Windows has several tools to administer, monitor, and troubleshoot DNS server operation, including:
DNS Manager
dcdiag /test:dns
dnscmd.exe
PowerShell
Event Viewer
dnslint
nslookup
ipconfig
Performance Monitor
Protocol analyzer
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

45. DNS Troubleshooting
In order to troubleshoot DNS queries you need a clear picture in your mind of the DNS lookup process, which involves the following steps:
1. Check the local DNS cache
2. Query the DNS server with a recursive lookup
3. Check the local zone data
4. Check locally cached data
5. Query root server or configured forwarders
DNS Troubleshooting
In order to troubleshoot DNS queries you need a clear picture in your mind of the DNS lookup process, which involves the following steps:
1. Check the local DNS cache
2. Query the DNS server with a recursive lookup
3. Check the local zone data
4. Check locally cached data
5. Query root server or configured forwarders
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

46. DNS Troubleshooting
To verify DNS configuration, use these ipconfig options:
/all - displays IP addresses of the configured DNS servers as well as the DNS suffix search list
/displaydns - displays the local DNS cache
/flushdns - deletes the local DNS cache
After these steps, double-check the Hosts file to make sure you didn’t miss something when you displayed the local cache
DNS Troubleshooting
To verify DNS configuration, use these ipconfig options:
/all - displays IP addresses of the configured DNS servers as well as the DNS suffix search list
/displaydns - displays the local DNS cache
/flushdns - deletes the local DNS cache
After these steps, double-check the Hosts file to make sure you didn’t miss something when you displayed the local cache
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

47. DNS Troubleshooting
If everything checks out on the client, you’ll need to analyze the DNS server the client uses, including the examining the following:
Locally cached data
DNS Server log
Verify Active Directory replication
Verify SRV records
Verify zone transfers
Verify zone delegations
Ping
Verify PTR records
DNS Troubleshooting
If everything checks out on the client, you’ll need to analyze the DNS server the client uses, including the examining the following:
Locally cached data
DNS Server log
Verify Active Directory replication
Verify SRV records
Verify zone transfers
Verify zone delegations
Ping
Verify PTR records
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

48. Summary
DNS is based on a hierarchical naming structure and a distributed database
DNS can be described as an inverted tree with the root domain at the top, TLDs branch- ing off the root, and domains and subdomains branching off TLDs
The DNS database is composed of zones containing resource records, such as Start of Authority (SOA), Host (A), and Service (SRV) records
DNS lookups involve iterative and recursive queries
Summary
DNS is based on a hierarchical naming structure and a distributed database
DNS can be described as an inverted tree with the root domain at the top, TLDs branch- ing off the root, and domains and subdomains branching off TLDs
The DNS database is composed of zones containing resource records, such as Start of Authority (SOA), Host (A), and Service (SRV) records
DNS lookups involve iterative and recursive queries
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

49. Summary
DNS servers can perform one or more of the following roles: authoritative server, for- warder, conditional forwarder, and caching-only server
A zone can be a forward lookup zone or a reverse lookup zone
DNS databases consist of the following types: primary zone, secondary zone, and stub zone
Active Directory–integrated zones have the advantages of automatic replication, multimaster replication and update, secure updates, and efficient replication
Summary
DNS servers can perform one or more of the following roles: authoritative server, for- warder, conditional forwarder, and caching-only server
A zone can be a forward lookup zone or a reverse lookup zone
DNS databases consist of the following types: primary zone, secondary zone, and stub zone
Active Directory–integrated zones have the advantages of automatic replication, multimaster replication and update, secure updates, and efficient replication
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam

50. Summary Resource records can be dynamically created or static records
SOA records contain information about a zone, including its serial number and a number of timers used for zone transfers
Advanced DNS settings include configuring forwarders, root hints, round robin, recursive queries, and logging
Tools for monitoring and troubleshooting DNS include dcdiag, dnscmd, dnslint, nslookup, ipconfig, PowerShell cmdlets, Performance Monitor, and protocol analyzers
Summary
Resource records can be dynamically created or static records
SOA records contain information about a zone, including its serial number and a number of timers used for zone transfers
Advanced DNS settings include configuring forwarders, root hints, round robin, recursive queries, and logging
Tools for monitoring and troubleshooting DNS include dcdiag, dnscmd, dnslint, nslookup, ipconfig, PowerShell cmdlets, Performance Monitor, and protocol analyzers
MCSA Guide to Installing and Configuring Windows Server 2012/R2, Exam