Bind server with logical host

[Kevin Darcy]

Nicholas F Miller wrote:
> We have upgraded our DNS servers recently to Bind 9.5. In the upgrade we
> also went to logical host names. There is now the host name and then the
> DNS server is plumbed as a logical host. Since we have done this we are
> seeing DNS answers happening on the host IP. We would like to restrict
> the DNS traffic to the logical host.
>
> Will the 'listen on' switch let us restrict the DNS traffic to our
> logical host IP?
>
>   
Listen-on won't *redirect* queries, if that's what you're asking. If 
clients are sending queries to the wrong IP, nothing you can do on the 
server side will stop that. listen-on can restrict whether you accept 
those packets or not, but if you don't accept them, the queries will 
simply time out and fail. Is that acceptable?

If the clients have both the Host IP and the "logical" IP in their 
resolver configs, in that order, then if you no longer listen on the 
Host IP, they may "transparently" fail over to the "logical" IP, but it 
won't be completely "transparent", in truth, since it will introduce a 
delay to every name lookup. Enough that some (impatient) apps may 
actually experience lookup failures. So do this at your own risk.

As for responses, named sends those back from the address on which the 
original query was received. So, if you can fix the clients to send 
their queries to the correct address in the first place, the responses 
will follow suit.

- Kevin