Difference between Conditional Forwarding and Delegation...

rgrizzaffirgrizzaffi Member Posts: 1 ■□□□□□□□□□
This is my first post on this site and I see that there is a lot of good people out there willing to help. Please can someone answer this question for me.

What is the difference between Conditional Forwarding and Delegation. Most importantly when would you use one over the other? Many practice questions always have both of these as possible answers but I never know which to pick.

I know the definitions of both but, they seem very similar in the end result. They both do name resolution.
I know that Conditional Forwarding is static and must be update manually. CF dosen't perform zone replication.
Delegations divide one or more name spaces into one or more zones. Can be distibuted and replicated to other DNS servers. I know the internet does a hell of alot of delegation but why would you do this over CF on internal DNS.
Plus dosen't CF provide a benifit for networks that have slower lans?

Does Conditional Forwarding provide fault tolerance?
If so, I've seen questions where they throw Stub Zones in the mix and then this really confuses they hell out of me. I know stub zones provide Fault tolerance and are dynamic but most of the time the question doesn't give you a hint on what to choose.

What should I look for in a question to easily identify which zone type to choose. There has always been some confusion on which I should pick.

Any help on this would be greatly appreciated.
Please let me know if I'm wrong in my knowlege of how either of these three zone types work.

Thanks in advance!


  • CorySCoryS Member Posts: 208
    Conditional forwarding is used for conditional requests, I think you are messing that term up with other types of zones. If you had a request for say "bamboo.net" and you knew that the only place you could resolve this was on one of your local servers you would enter that ip as a "conditional forwarder", from here you may or may not disable recursion to stop recursive queries from happening.

    For fault tolerance in a non domain environment you could use something like a secondary zone and if you ever had problems with your authoritative server you could switch the other dns servers zones to primary, this would provide fault tolerance.

    From what I understand delegated zones contain visibly (sp?) the name server record but hide on you the glue record.

    Stub zones are used when you want to replicate a copy of only a select few items from a zone (SOA, NS and Host records of the NS).

    Stub zones replicate via TCP not UDP like other zone transfers reducing network saturation and reduce overhead on other dns servers as you will now be able to send clients to the appropriate name servers.
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  • JdotQJdotQ Member Posts: 230
    Just to reiterate some stuff... (someone please correct me if I'm wrong)

    Conditional forwarding is used when you specify the DNS/name servers of a specific domain. For instance, if you know that CompanyABC.com domain has a DNS server at, then you can specify this, and reduce the time need to resolve the domain (as the query does not have to go out the Root domain and get referrals to downward domains). This is used mainly if two companies were to merge and you are combining two domains; you can have a conditional forwarder for CompanyA to point to CompanyB and vice versa. Conditional forwarding does not provide fault tolerance.

    Delegation is used when you want another server to manage the zone. For instance, if CompanyABC.com has two locations (East.CompanyABC.com and West.CompanyABC.com), and the top level wants the "east" office to manage their own zone, then CompanyABC.com can delegate East.CompanyABC.com down to a name server in that location. This allows for that location to answer queries for that specific zone, while the parent zone still has knowledge that the delegated zone is present. I don't believe delegation provides fault tolerance (someone confirm this?)

    Stub Zones act as dynamic "pointers" that just point to the name servers of a zone. In the zone that has a stub pointing to it, one server IP must remain constant, but any additional name servers that are added or deleted are automatically updated in the Stub Zone. This is used mainly in situations where a zone is constantly updating name servers (both adding and/or removing). A Stub Zone does not provide fault tolerance.

    Hope this helps!
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