Interview questions and answers on dns server n Windows 2003 and 2008
Q1. What is DNS?
Domain Name System is a service that can be installed on any windows server operating system to resolve the Name to IPAddress and vice-versa. TCP/IP networks, such as the Internet, use DNS to locate computers and services through user-friendly names
Q2. What is DDNS?
Dynamic DNS or DDNS is a method of updating, in real time, a Domain Name System to point to a changing IP address on the Internet. This is used to provide a persistent domain name for a resource that may change location on the network.
Q3. What are the resource records in DNS?
- A (Address) Maps a host name to an IP address. When a computer has multiple adapter cards and IP addresses, it should have multiple address records.
- CNAME (Canonical Name) Sets an alias for a host name. For example, using this record, zeta.tvpress.com can have an alias as www.tvpress.com.
- MX (Mail Exchange) Specifies a mail exchange server for the domain, which allows mail to be delivered to the correct mail servers in the domain.
- NS (Name Server) Specifies a name server for the domain, which allows DNS lookups within various zones. Each primary and secondary name server should be declared through this record.
- PTR (Pointer) Creates a pointer that maps an IP address to a host name for reverse lookups.
- SOA (Start of Authority) Declares the host that is the most authoritative for the zone and, as such, is the best source of DNS information for the zone. Each zone file must have an SOA record (which is created automatically when you add a zone).
Q4. What are a Forward and Reverse Lookup?
- Forward Lookup: When a name query is send to the DNS server against to IP address, it is generally said a forward lookup.
- Reverse Lookup: DNS also provides a reverse lookup process, enabling clients to use a known IP address during a name query and look up a computer name based on its address.
Q5. What is Primary zone?
This is the read and writable copy of a zone file in the DNS namespace. This is primary source for information about the zone and it stores the master copy of zone data in a local file or in AD DS. Dy default the primary zone file is named as zone_name.dns in %windir%\System32\DNS folder on the server.
Q6. What id Secondary zone?
This is the read only copy of a zone file in the DNS namespace. This is secondary source for information about the zone and it get the updated information from the master copy of primary zone. The network access must be available to connect with primary server. As secondary zone is merely a copy of a primary zone that is hosted on another server, it cannot be stored in AD DS.
Q7. What is stub Zone?
A stub zone is a read only copy of a zone that contains only those resource records which are necessary to identify the authoritative DNS servers for that particular zone. A stub zone is practically used to resolve names between separate DNS namespaces. This type of zone is generally created when a corporate merger or acquire and DNS servers for two separate DNS namespaces resolve names for clients in both namespaces.
A stub zone contains:
The start of authority (SOA) resource record, name server (NS) resource records, and the glue A resource records for the delegated zone.
The IP address of one or more master servers that can be used to update the stub zone.
Q8. What is Caching Only Server?
Caching-only servers are those DNS servers that only perform name resolution queries, cache the answers, and return the results to the client. Once the query is stored in cache, next time the query in resolved locally from cached instead of going to the actual site.
Q9. What is Aging and Scavenging?
DNS servers running Windows Server support aging and scavenging features. These features are provided as a mechanism to perform cleanup and removal of stale resource records from the server and zone. This feature removes the dynamically created records when they are stamped as stale.
By default, the aging and scavenging mechanism for the DNS Server service is disabled.
Scavenging and aging must be enabled both at the DNS server and on the zone
Q10. What is SRV record in DNS?
The SRV record is a resource record in DNS that is used to identify or point to a computer that host specific services i.e Active directory.
Q11. What is Forwarding in DNS?
A forwarder is a feature in DNS server that is used to forward DNS queries for external DNS names to DNS servers outside of that network. We ca configure a DNS server as a forwarder to forward the name query to other DNS servers in the network when they cannot resolve locally to that DNS server.
Q12. What is Conditional Forwarding in DNS?
We can configure the DNS server to forward queries according to specific domain names using conditional forwarders. In this case query is forward to an IP address against a DNS domain name.
- Q13. What are Queries types in DNS?
Recursive Query: This name queries are generally made by a DNS client to a DNS server or by a DNS server that is configured to pass unresolved name queries to another DNS server, in the case of a DNS server configured to use a forwarder.
- Iterative Query: An iterative name query is one in which a DNS client allows the DNS server to return the best answer it can give based on its cache or zone data. If the queried DNS server does not have an exact match for the queried name, the best possible information it can return is a referral. The DNS client can then query the DNS server for which it obtained a referral. It continues this process until it locates a DNS server that is authoritative for the queried name, or until an error or time-out condition is met.
Q13. What are Tools for troubleshooting of DNS?
DNS Console, NSLOOKUP, DNSCMD, IPCONFIG, DNS Logs.
Q14. How to check DNS health?
Using the DCdiag.
i.e. (dcdiag /test:dns /v /e)