"overlay" views

[Bob Harold]

On Mon, Jan 20, 2020 at 8:28 AM Brian J. Murrell <brian at interlinx.bc.ca>
wrote:

> I'm really not sure about what the name of this feature I am going to
> describe would be.  I would probably call it an "overlay view".  But I
> am sure there are better names.
>
> Imagine I have a BIND 9 server for the following network topology:
>
>
> Network 1
> 192.168.1.0/24           ------------------------
> -------------------------|.254                  |
>                          |       Router         |
> Network 2                |                      |
> 192.168.2.0/24           |                      |
> -------------------------|.254                  |
>                          |                      |
> Network 3                |                      |
> 192.168.3.0/24           |                      |
> -------------------------|.254                  |
>                          ------------------------
>
> There are a few dozen hosts/services on Network 3 which hosts from
> Network 1 and Network 2 need to resolve names of.  All pretty
> straightforward.
>
> But the hosts on Network 1 and Network 2 need to resolve the same name
> (let's call it "gateway") to the address of their interface on Router.
> So that is, hosts on Network 1 want a query of "gateway." to resolve to
> 192.168.1.254 and hosts on Network 2 want a query of "gateway." to
> resolve to  192.168.2.254.
>
> So this is currently all achievable through "views" in BIND 9, but
> requires that the zone data for each view be 98% duplicate (Network 3
> resources) and continually copy-n-paste updated whenever names on
> Network 3 are added.
>
> What I am looking for is a way to save the duplicate copying of Network
> 3 resources to the views for Network 1 and Network 2.  This is where
> the term "overlay" comes in.  What I'd like to do is reference a single
> copy of data from Network 3 in Network 1 and 2's views but "overlay"
> some view-specific resources on top of that, namely the "gateway."
> name, with it's per-view specific value.
>
> Thoughts?
>
> b.
>
>
What I have set up, is for the few names that need to be different, use
CNAME to a zone that is different in each view:

This zone is same in all views:
zone example.com
host1.example.com  IN  A  10.0.0.4
host2.example.com  IN  A  10.1.1.7
router.example.com  CNAME router.splitview.example.com

Then in one view:
zone splitview.example.com
router.splitview.example.com  IN A 10.0.0.1

And the other view:
zone splitview.example.com
router.splitview.example.com  IN  A 10.1.1.1

Any downsides that I have not thought about?

-- 
Bob Harold
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