BIND forwarders

[Chris Buxton]

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If named is looking something up that ends in ".mydomain.com" (or if  
the query name is "mydomain.com" itself), and if the server is not  
authoritative for the query name or any ancestor name, then named will  
forward the query as indicated.

Example: Suppose named has no zones of the following names: ".",  
"com", "www.mydomain.com". If the server is queried for "www.mydomain.com 
", and if the answer is not already in cache, the query will be  
forwarded. If the server is queried for "wwwmydomain.com" (missing a  
dot), the query will not be forwarded (at least not due to the forward  
zone shown).

As for fault tolerance between forwarders, this depends on your BIND  
version. With any current version of BIND, named tries to use RTT to  
pick the fastest forwarder; if a forwarder dies, the resolver will  
very quickly switch over to the other server. As Mark Andrews noted on  
this list not long ago, using RTT for forwarders is very, very tricky,  
and often does not result in any kind of predictable choice of  
forwarders from a list.

Chris Buxton
Professional Services
Men & Mice

On Aug 29, 2008, at 12:12 PM, Thilanka Samarasekera wrote:

> If I have a zone like the following:
> zone "mydomain.com" {
>        type forward;
>        forward only;
>        forwarders {
>                10.1.1.1;
>                10.1.1.2;
> };
> };
>
>
> Can someone explain to me the logic when it comes to using the  
> forwarders by
> the named process? Also, if for some reason "10.1.1.1" goes down,  
> what makes
> the named realize that the first forwarder in the list is down and  
> that it
> should now start forwarding to the second forwarder in the list.'
>
> Thank you in advance
>
> Thilanka
>
>
>

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