Share via

DNS: Difference between conditional forwarders and stub zones?

Question

Thursday, December 9, 2010 10:20 PM

Question says it all.  Thanks.

All replies (7)

Thursday, December 9, 2010 11:18 PM ✅Answered | 2 votes

They are completely different.

For one, Conditional Forwarding does not participate in zone transfers, while stub zones do.   Also, with conditional forwarding, when a query is sent to the DNS server, it will perform recursion and get the answer to the query.  With stub zones, a referral is given to the resolver (client).

With conditional forwarding, if the IPs change for the NS servers in the domain that you are forwarding to, you wouldnt know unless you were monitoring that or got a call from their DNS admin.  With stub zones, the SOA and NS records are updated through the zone transfer.

What is your scenrio and what are you trying to accomplish?

Visit: anITKB.com, an IT Knowledge Base.

Friday, December 10, 2010 5:57 AM ✅Answered

Hi,

Thanks for posting here.

You may take look the article below first to get a better undersatnding:

Contrasting stub zones and conditional forwarders

http://technet.microsoft.com/en-us/library/cc780434(WS.10).aspx

Thanks.

Tiger Li

TechNet Subscriber Support in forum
If you have any feedback on our support, please contact [email protected]

Please remember to click “Mark as Answer” on the post that helps you, and to click “Unmark as Answer” if a marked post does not actually answer your question. This can be beneficial to other community members reading the thread.

Friday, December 10, 2010 3:04 PM

Alright guys.....

 

Let me recheck my thinking here.

 

A conditional forwarder is something that you would use to tell clients "go to this server if you are looking for information for a query for this particular external domain and they will tell you where to go for them.  I'm not going to do a recursive query for those domains.  Let that server handle it.  Go ask that server."

 

A stub zone is used for internal child domains to keep a parent server of a child domain updated with the proper address of the authoritative server for a child domain.  For example if you have domain test.com for parent and it has child domains of east.test.com and west.test.com.  You would create a stub zone for each ot the 2 child domains on the authoritative server for test.com so that it knows what the east and west domain authoritative servers are located even if they change.  If they change, the east and west server will update the stub zone on the authoritative server for test.com because there is a stub zone in its dns.  Is that right at all?

Thanks!

Saturday, December 11, 2010 3:31 PM

1) No, With a conditional forwarder the DNS server does not give the resolver (dns client) a referral.  It will perform a recursive query, get the answer and respond back to the resolver.

2) The stub zone can be used for any type of domain (internal or extrenal).Yes to the rest of what you wrote about stub zones.

The best way to see this and learn about DNS is to build the components in a lab and run a packet capture to examine the flow of packets.

Visit: anITKB.com, an IT Knowledge Base.

Monday, December 13, 2010 2:35 AM

1) No, With a conditional forwarder the DNS server does not give the resolver (dns client) a referral.  It will perform a recursive query, get the answer and respond back to the resolver.

2) The stub zone can be used for any type of domain (internal or extrenal).Yes to the rest of what you wrote about stub zones.

The best way to see this and learn about DNS is to build the components in a lab and run a packet capture to examine the flow of packets.

Visit: anITKB.com, an IT Knowledge Base.

1.  okay so what is the difference between having a conditional forwarder involved in this recursive query or just letting the server do it like normal?  I don't see how this any different than what the server would normally do for an external request it cant' resolve.

2. If this is true with stub zones being used for external domains, how does the external domain know to update the server you put the stub zone on?

Thanks for working with me on this.

Monday, December 13, 2010 2:26 PM | 2 votes

1) I think we are saying the same thing here.   A DNS server will either perform a recursive or iterative query, depending on its configuration.  For most DNS implementations, especially internal ones, your DNS servers are configured to perform recursion, that is, if it does not have the answer to the query by using its cache or local hosted zones, it will go out and find the answer for the clients, either by using its root hints or forwarder information.  When you host an external DNS server, you would normally disable recursion so that your DNS server will only answer queries for the zones it hosts.  For example, if you have a company that sells widgets and you host your external zone, you really shouldn't interested in resolving queries on that DNS server for anything other than widgets.com.  If you leave recursion enabled on the external DNS server, internet users can use your DNS server for resolving any host name.

2) Think of the stub zone as a secondary zone except without any of the records other than the SOA and NS.  Your server will attempt a zone transfer from the one of more of the NS servers listed in the stub zone.  As the SOA and NS records are updated, your server has the new information, such as if an NS record is added or removed.  Of course, if you stub zone only knew about ONE primary DNS server and that primary DNS server were to change its IP, the server hosting the stub would have no way of find any new information. 

Most most situations, I would tend to use forwarders over stub zones, but you have to take into account the overall design and goals.

 

Visit: anITKB.com, an IT Knowledge Base.

Saturday, August 20, 2016 10:59 AM

You should consider using stub zones in multisite scenarios where replication of large zone may be an issue. This is only advantage of stubzone.