On 1/19/2013 6:00 AM, bind-users-requ...@lists.isc.org wrote:
On Jan 16, 2013, at 1:01 PM, Chuck Swiger wrote:
>On Jan 16, 2013, at 12:40 PM, Dave Warren wrote:
>>Is there anything technically wrong with having a SOA MNAME field that isn't
listed as a NS record?
>
>Sure. The SOA MNAME is expected to be the "primary master" nameserver for the
zone; it's where things like dhcpd and such send dynamic updates for the zone to.
No, not necessarily, not if there's no NS record for it.
RFC 2136 says says that the server "as given by the SOA MNAME field if matched by
some NS NSDNAME" should be the preferred target of a dynamic update. That is, if the
master server (as indicated by the SOA record) is not listed in an NS record as an
authoritative name server, it need not be considered. However, the RFC is a bit vague on
how a requestor determines (and orders) the list of authoritative name servers for a
zone, and so...
- ISC DHCP sends DDNS updates to the SOA MNAME server if and only if that
server is also listed in an NS record. Otherwise, it picks a name from the
available NS records and sends the update there. This behavior can be
overridden by a zone statement in dhcpd.conf.
- Microsoft clients send DDNS updates to various places, and will typically try
multiple targets if the update is denied. I believe the order is the first
configured caching resolver, the zone's MNAME field, and then any one of the
servers listed in the NS RRSet. I believe the client will try three times,
assuming these three cases are all different. (I'm not counting potential
retries to the same target to attempt use of GSS-TSIG.)
I believe nsupdate behaves the same as dhcpd, but it's been a while since I
last tested this.
Chris Buxton
BlueCat Networks
The last time I checked (a number of years ago) there was no non-draft
RFC covering the DHCP-DNS interaction. So, when a DHCP server wants
to send a DDNS packet to a DNS server, there is no standard stating
which DNS server should be the recipient of the packet.
--Barry Finkel
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