How do DNS Clients use a Caching only or Secondary DNS Server with Dynamic Updats?

I am studying the MS course material and cannot find an answer to the
subject question. MS has scenarios where they recommend caching only or
secondary zone servers at remote sites. If the clients there are AD clients
who register their records with a Primary DNS server, how do they recognize
the non-Primary servers for use? Alternatively, if they are told to use a
secondary zone or caching server as their primary DNS server, how do their
dynamic DNS updates get registered on the primary? The material does not
address this & I have been unable to find the answer using web resources so
far.

 

Only Active Directory integrated or primary zones can register dns clients.
Secondary zones are authoritative for a zone but can not register a dns
record for the zone. Secondary zones pull there zone info from a master dns
server. Secondary zones are useful when you need to resolve names in another
dns zone and both an Active Directory integrated/primary and secondary zone
can be on the same dns server but not for the same zone. For instance say
you are in a forest with acme.com and gloop.com and you are in acme.com.
Your preferred dns server would probably be a domain controller in acme.com
and have the AD integrated zone for acme.com which would register your dns
record dynamically. Since you also need to access resources in gloop.com and
they have their own domain controllers running dns, your preferred dns
server could be configured to have a secondary zone for gloop.com. Now your
preferred dns server can resolve names for both domains in the forest AND
resolve internet names for your computer because it is configured to forward
to the ISP dns server for zones it is not authoritative.

Caching dns servers have no domain zones so they are not authoritative for
any dns zone nor can they register any dns records. They can however be
configured to forward to other dns servers that can resolve dns names. Once
they start forwarding and dns names are resolved they "cache" the dns
replies from the forwarder and subsequent dns queries sent to it are first
checked for existence in the cache and then cached info is used if available
or off to the forwarder the query goes. This can help for a remote site
belonging to the domain that has a slow link. One way would be to configure
the caching dns server to forward to an Active Directory dns server at the
main site. Eventually both internet and domain records would be cached on
the caching server and that would improve response at the remote site and
reduce traffic over the slow link. The remote site computers would still be
able to locate the AD dns server when the needed to register or update their
dns records. --- Steve

 

If I am reading your reply correctly, then a resolver can have its primary
DNS server at a remote site set to the address of the zone primary server at
the main site. When the client tries to register its address record on boot
up the caching server will forward the registration query to the primary
server. When the client resolver sends a query to resolve a friendly name
to address, the caching server will anser it if it's cached, or forward the
query to the forwarder (in this case the primary zone AD server) in a
recursive query, then cache the results.

Have I got it straight?

Brian

 

In such a situation put the caching dns server first in the list of
preferred dns servers for domain clients at the remote site and the AD dns
server at the main site second in the list. That way it will always try to
use the caching dns server first and the main site dns server only if it can
not contact the caching dns server for redundancy. The caching server will
either resolve the request for the domain client computer from it's cache or
from the AD dns servers it forwards to. The caching dns server itself will
need to be configured to forward to AD dns servers in the main site. ---
Steve