Internet and especially the web are based on the DNS system and the very large number of domain names that exist at the moment. If you have already bought a domain name on the Internet or consulted the whois of a domain, you will have surely noticed that the domain is always managed by at least 2 DNS servers created by the host where the user bought his domain name. Since only one DNS server can be authoritative for each zone, it was necessary to find a technique to obtain a certain fault tolerance.
This technique consists in creating at least 2 DNS servers :. Specify the name of the zone that you manage on your primary DNS server and that you want to replicate to your secondary DNS server. Note : selecting the "Only to the following servers" option by specifying the IP address of the secondary DNS server would also work.
However, since you must also add the IP address of the secondary server as a name server for the concerned zone, it's preferable to use the "Only to servers listed on the Name Servers tab" option. As you can see, our secondary DNS server ns2 is well referenced as a name server for this zone.
If we try to get the IP address corresponding to the "ns1. As explained in our previous tutorial, for each change, Windows Server automatically increment the serial number of the zone.
When the client receives a response to this query, the client sends an SOA query to the first DNS server that is listed in the response. After the SOA query is resolved, the client sends a dynamic update to the server that is specified in the returned SOA record. If this update fails, the client repeats the SOA query process by sending to the next DNS server that is listed in the response.
After the primary server that can perform the update is contacted, the client sends the update request, and the server processes it. The contents of the update request include instructions to add A, and possibly PTR, resource records for " newhost. The server also checks to make sure that updates are permitted for the client request. For standard primary zones, dynamic updates are not secured.
Any client attempt to update succeeds. For Active Directory-integrated zones, updates are secured and performed using directory-based security settings. Dynamic updates are sent or refreshed periodically. By default, computers send an update every twenty-four hours. If the update causes no changes to zone data, the zone remains at its current version, and no changes are written.
Updates that cause actual zone changes or increased zone transfers occur only if names or addresses actually change.
Names are not removed from DNS zones if they become inactive or if they are not updated within the update interval of twenty-four hours. DNS does not use a mechanism to release or to tombstone names, although DNS clients do try to delete or to update old name records when a new name or address change is applied. This value determines how long other DNS servers and clients cache a computer's records when they are included in a query response.
Scope clients can use the DNS dynamic update protocol to update their host name-to-address mapping information whenever changes occur to their DHCP-assigned address.
This mapping information is stored in zones on the DNS server. This enables the client to notify the DHCP server as to the service level it requires. In this case, the option is processed and interpreted by Windows Server-based DHCP servers to determine how the server initiates updates on behalf of the client.
This is the default configuration for Windows. To configure the DHCP server to register client information according to the client's request, follow these steps:. By default, updates are always performed for newly installed Windows Server-based DHCP servers and any new scopes that you create for them. The following examples show how this process varies in different cases. For these DHCP clients, updates are typically handled in the following manner:.
After you integrate a zone, you can use the access control list ACL editing features that are available in the DNS snap-in to add or to remove users or groups from the ACL for a specific zone or for a resource record. For more information, search for the "To modify security for a resource record" topic or the "To modify security for a directory integrated zone" topic in Windows Server Help.
By default, dynamic update security for Windows Server DNS servers and clients is handled in the following manner:. Windows Server-based DNS clients try to use nonsecure dynamic updates first. If the nonsecure update is refused, clients try to use a secure update.
Also, clients use a default update policy that lets them to try to overwrite a previously registered resource record, unless they are specifically blocked by update security. By default, when you use standard zone storage, the DNS Server service does not enable dynamic updates on its zones.
For zones that are either directory-integrated or use standard file-based storage, you can change the zone to enable all dynamic updates. This enables all updates to be accepted by passing the use of secure updates. The secure dynamic updates functionality can be compromised if the following conditions are true:. For more information, see the "Security considerations when you use the DnsUpdateProxy group" section.
The secure dynamic update functionality is supported only for Active Directory-integrated zones. If you configure a different zone type, change the zone type, and then integrate the zone before you secure it for DNS updates. If you use secure dynamic updates in this configuration with Windows Server-based DNS servers, resource records may become stale.
In some circumstances, this scenario may cause problems. For example, if DHCP1 fails and a second backup DHCP server comes online, the backup server cannot update the client name because the server is not the owner of the name. In another example, assume that the DHCP server performs dynamic updates for legacy clients. If you upgrade those clients to a version supporting dynamic updates, the upgraded client cannot take ownership or update its DNS records.
For example, to add a new child domain named na. If an authoritative DNS server for the newly delegated na. These resource records include the following:. Follow the steps in the New Delegation Wizard to create the delegation.
0コメント