Another way to find the primary server for a zone

[Kevin Darcy]

Jim Reid wrote:

> >>>>> "Elisabeth" == ELISABETH CHORQUES <ELISABETH.CHORQUES at ALCATEL.FR> writes:
>
>     Elisabeth>  Hello!  I work with Bind 8.2.3 I have read that to
>     Elisabeth> find the primary server for a zone, we have to read the
>     Elisabeth> "SOA" record for the zone and to check if the name of
>     Elisabeth> the server is given in the first field of the record
>     Elisabeth> like that: dom.name.zone 12H IN SOA ns.dom.name.zone
>     Elisabeth> The DNS whose name is "ns" is declared primary for the
>     Elisabeth> zone "dom.name.zone".
>
> This is correct. However it is not mandatory to identify the master
> (primary) server for a zone in this way. Many people put any old junk
> in the MNAME field of the SOA record. However if you plan to use
> Dynamic DNS (DDNS), you *must* provide the name of the master server
> in the MNAME. This is the only way for DDNS clients to find out where
> to send their dynamic update requests.

Actually, that's not technically true. According to RFC 2136, the requestor should
only give preference to the MNAME server if it "has reasonable cause to believe
that all of a zone's servers will be equally reachable". If it has
"special" knowledge that one server is more reachable than the others, then it can
ignore the MNAME. In practical terms, this can be accomplished using the
"server" command in BIND 9's nsupdate.


- Kevin