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Asked: 2016-08-26 02:18:51 +0800 CST

active directory: what is the semantic of the integer values associated to DNS SRV records?

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Starting from the following example (citated on samba wiki):

$host -t SRV _ldap._tcp.samdom.example.com.
_ldap._tcp.samdom.example.com has SRV record 0 100 389 dc1.samdom.example.com.

What do the integers in the response mean?

389 is likely the TCP port involved, but 0? and 100?

domain-name-system active-directory

2 Answers

  1. Best Answer

    Let's have a look at RFC 2782, A DNS RR for specifying the location of services (DNS SRV)

    The format of the SRV RR

    Here is the format of the SRV RR, whose DNS type code is 33:

    _Service._Proto.Name TTL Class SRV Priority Weight Port Target

    So although your example does not list TTL, we do know its class is IN and that its type is SRV...

    _ldap._tcp.samdom.example.com 0 100 389 dc1.samdom.example.com.

    • Name _ldap._tcp.samdom.example.com
    • Priority 0
    • Weight 100
    • Port 389
    • Target dc1.samdom.example.com.

    From AD Windows DC

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  2. Priority and weight:

    https://en.m.wikipedia.org/wiki/SRV_record

    Lower priority (0) is more preferred.

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