Multiple views (more than 2)

[Marek Kozlowski]

:-)

Till now I've been using sth. like this for a single private and a 
single public views:

https://kb.isc.org/docs/aa-00851

For my clients I provided information on all my resources and recursive 
resolution, for external ones - about my public hosts and no recursive 
resolution. Trivial.

But there is a new concept:

For some reasons (its not my decision) workstations cloned from a single 
image (precisely: a few images of Windows, Linux and other systems) 
connected to different subnets should refer to different hosts for 
numerous services based on their CIDR prefixes. Don't ask me why not use 
/etc/hosts nor distribute parameters via DHCP - it's not my decision. I 
am responsible, as a DNS server administrator, for providing different 
answers to queries about A records based on client's IP (CIDR prefix). 
That is what views can do.

Defining views for a single DNS server itself is trivial. The problem is 
setting up zone transfers of different zone description files (from 
different views) between many name servers. In my case:

Zone description files from public view should be transferred from 
Primary to all three Secondary DNS servers (I'm supervising only two of 
them). All zone description files from all private views should be 
transferred from my Primary to my (internal) Secondary (into respective 
views) and NOT to external secondaries.

AFAIK such a configuration of view transfers requires TSIGs for avoiding 
zone transfer overwriting.

Best regards,
Marek

On 4/14/25 5:27 PM, Greg Choules wrote:
> Hi Marek.
> Please can you show the config that used to work?
> Please can you also explain why it is desired to create more views? 
> Maybe give an example of what you're trying to achieve.
> 
> In general, matching views is done top down - test clients against the 
> criteria in the first view. If they don't match, try the next view etc.
> 
> "match-clients" is used to test whether the source address of the client 
> falls within the range allowed by the address match list specified.
> "match-destinations" is used to test the destination address the 
> incoming query was sent to. It is not unusual to have a server listen-on 
> several addresses, each for a different set of clients.
> Both of the above can be used together to make view selection even 
> tighter - clients must match against both their source address AND the 
> address they sent the query to.
> 
> Keys - as criteria for matching views - are typically used between 
> servers for zone transfers. For example if your primary server has 
> multiple views and secondary servers must be directed to a specific view 
> for a given zone, keys can be set up at both ends so that the secondary 
> includes the key for a zone when making its transfer request and the 
> primary uses that to select the correct zone from the appropriate view. 
> End clients/stub resolvers don't typically use keys.
> 
> I hope this helps.
> Cheers, Greg
> 
> 
> On Mon, 14 Apr 2025 at 14:12, Marek Kozlowski 
> <m.kozlowski at mini.pw.edu.pl <mailto:m.kozlowski at mini.pw.edu.pl>> wrote:
> 
>     :-)
> 
>     There are 4 name servers for my domain: two internal ones (my CIDR,
>     managed by me) and two external ones (foreign IP, I have no
>     administrative privileges).
> 
>     I've been using two views: the private one (for my clients, served
>     by my
>     servers) and a public one (for remote clients, served by all four name
>     servers). It used to work :-)
> 
>     Now it's desired to create multiple different private views served
>     by my
>     name servers (one view for clients from each subnet of my network)
>     and a
>     single public view (the same as till now) and I'm getting a bit
>     confused
>     with keys and "match-clients" directives...
> 
>     Any example, link, general formula or some smart how-to, or anything
>     welcome...
> 
>     Thanks a lot!
>     Best regards,
>     Marek
> 
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