MX preference, distance, and priority Īccording to RFC 5321, the lowest-numbered records are the most preferred. The MX mechanism does not grant the ability to provide mail service on alternative port numbers, nor does it provide the ability to distribute mail delivery across a set of unequal-priority mail servers by assigning a weighting value to each one. The system allows high-availability clusters of mail gateways to be built for one domain if necessary. The sending agent then attempts to establish an SMTP connection, trying the host with the lowest "Priority" value first. This query returns a list of host names of mail exchange servers accepting incoming mail for that domain and their preferences. When an e-mail message is sent through the Internet, the sending mail transfer agent (MTA) queries the Domain Name System for the MX records of each recipient's domain name. The host name must map directly to one or more address records (A, or AAAA) in the DNS, and must not point to any CNAME records. The priority field identifies which mailserver should be preferred - in this case the values are both 10, so mail would be expected to flow evenly to both and - a common configuration. The characteristic payload information of an MX record is a preference value (above labelled "Priority"), and the domain name of a mailserver ("Host" above). An MX record is one of these, and a domain may have one or more of these set up, as below:Į. Resource records are the basic information element of the Domain Name System (DNS). It is possible to configure several MX records, typically pointing to an array of mail servers for load balancing and redundancy. It is a resource record in the Domain Name System (DNS). Domain_Name internet address = Server_IP_Addressįor more information about the SRV records that are registered by Netlogon, see SRV Records Registered by NetLogon.Type of resource record in the Domain Name System (DNS)Ī mail exchanger record ( MX record) specifies the mail server responsible for accepting email messages on behalf of a domain name. Nslookup returns one or more SRV service location records that appear in the following format, where is the host name of a domain controller, and where is the domain where the domain controller belongs to, and is the domain controller's Internet Protocol (IP) address: Server: localhost Type _ldap._tcp.dc._msdcs.Domain_Name, where is the name of your domain, and then press ENTER.Type set type=all, and then press ENTER.To use Nslookup to verify the SRV records, follow these steps: Nslookup is a command-line tool that displays information you can use to diagnose Domain Name System (DNS) infrastructure. This record should appear similar to the following one: The first record in the file is the domain controller's Lightweight Directory Access Protocol (LDAP) SRV record. You can use a text editor, such as Notepad, to view this file. Netlogon.dns is located in the %systemroot%\System32\Config folder. If you're using non-Microsoft DNS servers to support Active Directory, you can verify SRV locator resource records by viewing Netlogon.dns. In these locations, an SRV record should appear for the following services: Forward Lookup Zones/Domain_Name/_msdcs/dc/_tcp.Forward Lookup Zones/Domain_Name/_msdcs/dc/_sites/Default-First-Site-Name/_tcp.Method 1: Use DNS ManagerĪfter you install Active Directory on a server that's running the DNS service, you can use the DNS Management Console to verify that the appropriate zones and resource records are created for each DNS zone.Īctive Directory creates its SRV records in the following folders, where is the name of your domain: To verify SRV locator resource records for a domain controller, use one of the following methods. SRV resource records are used to locate domain controllers for Active Directory. It's used to identify computers hosting specific services. The SRV record is a Domain Name System (DNS) resource record. This article describes how to verify Service Location (SRV) locator resource records for a domain controller after you install the Active Directory directory service.Īpplies to: Windows Server 2012 R2 Original KB number: 816587 Summary
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