round robing / load balancind

[Kevin Darcy]

Read the parts of RFCs 1035 and 2821 which deal specifically with
MX records. The numbers are "preference values". Put simply, records with
lower preference values are used before ones with higher preference values.
In the case of equal preference values, mailers are supposedly to pick them
randomly.


- Kevin

sebastien at willemijns.com wrote:

> i try to understand how DNS choose an MX server ie smtp.free.fr
>
> Querying Mail routing information (mx) for free.fr
> ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 51213
> ;; flags: qr rd ra; QUERY: 1, ANSWER: 6, AUTHORITY: 0, ADDITIONAL: 0
> ;;      free.fr, type = MX, class = IN
> free.fr.                0S IN MX        50 mrelay2-2.free.fr.
> free.fr.                0S IN MX        90 ns1.proxad.net.
> free.fr.                0S IN MX        10 mx.free.fr.
> free.fr.                0S IN MX        20 mrelay1-1.free.fr.
> free.fr.                0S IN MX        30 mrelay1-2.free.fr.
> free.fr.                0S IN MX        40 mrelay2-1.free.fr.
>
> what is this number ? 50, 90, 10, 20...etc...
>
> how to detect if a server FREE.FR in my example use round robing or load
> balancing ? must i connect to the free.fr name server to know this ?