A DNS zone is the contiguous portion of the DNS area identify area over which a DNS server has authority or is authoritative. DNS zones include both domains or subdomains. The DNS namespace could be divided into a number of zones. Customers may even host all their zones on a single DNS server. The Home windows Server 2003 DNS Server can host as much as 20,000 DNS zones.
A DNS zone accommodates a zone database that accommodates useful resource data for all of the domains inside the zone. Zone information are used if DNS is just not built-in with Lively Listing. The zone information include the DNS database useful resource data that outline the zone. If DNS and Lively Listing are built-in, zone knowledge is saved in Lively Listing.
The several types of zones that may be configured in Home windows Server 2003 DNS are:
- Main zone: That is the one zone sort that may be edited or up to date as a result of the info within the zone is the unique knowledge supply for all domains within the zone. The DNS server that’s authoritative for the precise main zone makes updates to the first zone. Knowledge may also be backed up from a main to a secondary zone.
- Secondary zone: A secondary zone is a read-only copy of the zone that was copied from the grasp server throughout zone switch.
- Lively Listing-integrated zone: An Lively Listing-integrated zone is a zone that shops its zone knowledge in Lively Listing. DNS zone information will not be used to retailer knowledge for these zones. An Lively Listing built-in zone is an authoritative main zone. An Lively Listing-integrated zone’s zone knowledge is replicated in the course of the Lively Listing replication course of. That is the one DNS zone sort that may use multi-master replication and the Lively Listing’s security measures.
- Reverse lookup zone: Reverse look-up zones are are primarily used to resolve IP addresses to useful resource names on the community. Ahead lookup zones include identify to IP handle mappings, whereas reverse lookup zones include IP tackle to call mappings.
- Stub zone: A stub zone is a brand new Home windows Server 2003 function. Stub zones solely include these useful resource data essential to determine the authoritative DNS servers for the grasp zone. Stub zones include the next:
- Begin Of Authority (SOA) useful resource document for the zone.
- Identify Server (NS) useful resource report for the zone.
- Host (A) useful resource data that determine the authoritative servers for the precise zone.
Zone switch is the method that copies a zone file’s useful resource data on the first DNS server to the secondary DNS servers. A secondary DNS server can even switch its zone knowledge to different secondary DNS servers which are beneath it within the DNS hierarchy. On this case, the secondary DNS server is considered the grasp DNS server to the opposite secondary servers.
The zone switch strategies that may be configured are:
- Full switch: When customers configure a secondary DNS server for a zone and begin the secondary DNS server, the secondary DNS server requests a full copy of the zone from the first DNS server. All the zone info is absolutely transferred. Full zone transfers are typically useful resource intensive. This drawback has led to the event of incremental zone transfers.
- Incremental zone switch: With an incremental zone switch, solely these useful resource data which have since modified in a zone are transferred to the secondary DNS servers. Throughout zone switch, the DNS databases on the first DNS server and the secondary DNS server are in comparison with decide whether or not there are variations within the DNS knowledge. If the DNS knowledge of the first and secondary DNS servers are the identical, zone switch doesn’t happen. If the 2 servers’ DNS knowledge are totally different, delta useful resource report switch begins. This happens when the serial quantity on the first DNS server database is greater than the secondary DNS server’s serial quantity. For incremental zone switch to happen, the first DNS server has to document incremental modifications to its DNS database. Incremental zone transfers require much less bandwidth than full zone transfers.
- Lively Listing transfers: These zone transfers happen when Lively Listing-integrated zones are replicated to the area controllers in a website. Replication happens via Lively Listing replication.
- DNS Notify is a mechanism that permits a main DNS server to tell secondary DNS servers when its database has been up to date. DNS Notify informs the secondary DNS servers when they should provoke a zone switch in order that the first DNS server’s updates could be replicated to them. When a secondary DNS server receives the notification from the first DNS server, it will possibly begin an incremental zone switch or a full zone switch to tug zone modifications from the first DNS servers.
Figuring out DNS Useful resource Report (RR) Necessities
The generally used useful resource data (RR) are:
- Begin of Authority (SOA): The SOA document is the primary report within the DNS database file. The SOA report consists of info on zone properties, akin to the first DNS server for the zone and the database’s model quantity.
- Identify Server (NS): The Identify Server (NS) useful resource document offers an inventory of the authoritative DNS servers for a website and an authoritative DNS server for any delegated subdomains.
- Host (A): The host (A) useful resource document incorporates a selected host’s IP handle and maps the FQDN to this 32-bit IPv4 addresses. Host (A) useful resource data principally affiliate the computer systems’ domains (FQDNs) or hosts names to their IP addresses.
- Alias (CNAME): Alias (CNAME) useful resource data ties an alias identify to its related area identify. Alias (CNAME) useful resource data are known as canonical names. Through the use of canonical names, community info may be hidden from the shoppers who hook up with a community.
- Mail exchanger (MX): The mail exchanger (MX) useful resource report offers routing for messages to mail servers and backup servers. The MX useful resource document supplies info on which mail servers course of e-mail for the actual area identify.
- Pointer (PTR): The pointer (PTR) useful resource document is used for reverse lookups to level to A useful resource data. Reverse lookups resolve IP addresses to host names or FQDNs.
- Service location (SRV): Lively listing sometimes makes use of Service (SRV) useful resource data to find area controllers, LDAP servers, and international catalog servers.
The primary useful resource data that determine hosts on a DNS community are:
- Begin of Authority (SOA)
- Tackle data: A and AAAA data
- Canonical Identify (CNAME) or Alias report
For Lively Listing to function, DNS servers that host Lively Listing-integrated zones should help the (SRV) useful resource data outlined in RFC 2052: DNS RR for specifying the situation of providers (DNS SRV). This is because of shoppers and area controllers querying DNS for SRV data when they should find a website controller’s IP addresses.
Figuring out Zone Necessities
When figuring out the way to break up the DNS namespace into zones, maintain the next elements in thoughts:
- Transferring zone information between zones will increase DNS zone switch visitors and Lively Listing replication visitors.
- Decide the visitors patterns that exist between shoppers and the DNS server. Pay cautious consideration to queries which are being handed over WAN connection. The System Monitor software can be utilized to acquire DNS server statistics.
- Think about the community hyperlinks between DNS servers and the velocity of those hyperlinks.
- Decide whether or not full DNS servers or caching-only DNS servers are required for the totally different places.
Main Zones versus Lively Listing-integrated Zones
When deciding whether or not to implement main DNS zones or Lively Listing-integrated DNS zones, keep in mind to incorporate the setting’s DNS design necessities. Main zones and secondary zones are commonplace DNS zones that use zone information. An Lively Listing-integrated zone shops its zone knowledge in Lively Listing and may subsequently use multi-master replication and Lively Listing’s security measures.
When implementing Lively Listing-integrated zones, select between the next zone replication scope choices:
- To All DNS Servers In The Lively Listing Forest choice: Zone knowledge is replicated to all DNS servers operating on area controllers within the Lively Listing forest.
- To All DNS Servers In The Lively Listing Area choice: Zone knowledge is replicated to all DNS servers operating on area controllers within the Lively Listing area.
- To All Area Controllers In The Lively Listing Area choice: Zone knowledge is replicated to all area controllers within the Lively Listing area.
- To All Area Controllers Specified In The Scope Of The Following Software Listing Partition choice: Zone knowledge is replicated based mostly on the replication scope of the actual software listing partition.
The primary benefits that Lively Listing-integrated zones have over commonplace main DNS zones are:
- Lively Listing replication is quicker, which signifies that the time wanted to switch zone knowledge between zones is way much less.
- The Lively Listing replication topology is used for Lively Listing replication and for Lively Listing-integrated zone replication. There isn’t a longer a necessity for DNS replication when DNS and Lively Listing are built-in.
- Lively Listing-integrated zones can take pleasure in Lively Listing’s security measures.
- The necessity to handle Lively Listing domains and DNS namespaces as separate entities is eradicated. This in flip reduces administrative overhead.
- When DNS and Lively Listing are built-in, the Lively Listing-integrated zones are replicated and saved on any new area controllers routinely. Synchronization takes place mechanically when new area controllers are deployed.
Figuring out Zone Placement
The method that DNS makes use of to ahead a question that one DNS server can’t resolve to a different DNS server is known as DNS forwarding. DNS forwarders are the DNS servers used to ahead DNS queries for various DNS namespaces to these DNS servers who can reply the question. Creating DNS forwarders can enhance identify decision effectivity.
Home windows Server 2003 DNS introduces a function referred to as conditional forwarding. With conditional forwarding, customers create conditional forwarders inside their setting that may ahead DNS queries based mostly on the precise domains being requested within the question. This differs from DNS forwarders the place the usual DNS decision path to the basis was used to resolve the question. A conditional forwarder can solely ahead queries for domains which are outlined within the specific conditional forwarders record. The question is handed to the default DNS forwarder if there are not any entries within the forwarders listing for the precise area queried.
When planning a DNS surroundings and it’s evident that forwarders or conditional forwarders must be carried out, think about the suggestions for planning forwarders which might be summarized under:
- Use forwarders to restrict the variety of DNS servers which have to speak between one another over firewalls. This technique enhances DNS safety.
- Customers may also improve fault tolerance by configuring a number of forwarders and enabling recursion for these queries that can’t be forwarded to the required forwarders.
- Solely implement the variety of DNS forwarders which might be mandatory for the surroundings. Chorus from creating a great deal of forwarders for inner DNS servers.
- Keep away from chaining DNS servers collectively in a forwarding configuration.
- To keep away from the DNS forwarder turning right into a bottleneck, don’t configure one exterior DNS forwarder for all the interior DNS servers.
Suggestions for Figuring out Zone Replication
Numerous suggestions for planning for zone replication are famous under:
- Restrict the variety of zones of authority inside the DNS setting. The extra authority zones there are, the larger the executive effort required to handle the DNS setting.
- Transferring zone information between zones will increase DNS zone switch visitors and Lively Listing replication visitors.
- To attenuate zone switch visitors when the DNS servers exist on Home windows Server 2003 area controllers and Lively Listing-integrated zones are getting used, think about using the appliance listing partition for storing zone knowledge.
- If utilizing commonplace DNS zone transfers, it’s useful to implement the next:
- Incremental zone transfers
- Quick zone transfers
- To scale back the bandwidth that commonplace DNS zone transfers use, think about altering the schedule for zone transfers to the secondary DNS zones.
- Think about implementing stub zones to attenuate DNS visitors.
- Use Lively Listing-integrated zones to specify that solely safe updates to the zones are allowed.
- To safe zone knowledge of the usual zone varieties, contemplate implementing the next:
- Restrict the variety of hosts which might be allowed to obtain zone transfers.
- Encrypt zone switch knowledge by way of VPN tunnels or IPSec.
How one can Create a DNS Zone
- Click on Begin, Administrative Instruments, then DNS to open the DNS console.
- Increase the Ahead Lookup Zones folder.
- Choose the Ahead Lookup Zones folder.
- From the Motion menu, choose New Zone.
- The New Zone Wizard initiates.
- On the Wizard’s preliminary web page, click on Subsequent.
- On the Zone Sort web page, be sure that the Main Zone Creates A Copy Of A Zone That Can Be Up to date Immediately On This Server choice is chosen. This feature is chosen by default.
- Uncheck the Retailer The Zone In Lively Listing (Out there Solely If DNS Server Is A Area Controller) checkbox. Click on Subsequent.
- On the Zone Identify web page, enter the right identify for the zone within the Zone Identify textbox. Click on Subsequent.
- On the Zone File web page, make sure that the default choice, Create A New File With This File Identify is chosen. Click on Subsequent.
- On the Dynamic Replace web page, make sure that the Do Not Permit Dynamic Updates. Dynamic Updates Of Useful resource Data Are Not Accepted By This Zone. You Should Replace These Data Manually choice is chosen. Click on Subsequent.
- The Finishing The New Zone Wizard web page is displayed subsequent.
- Click on End to create the brand new zone.
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