round robin, prioritize DNS results

[Kevin Darcy]

Nikos Voutsinas wrote:

> Hello,
>
> I have nine servers spread all over my country. Those servers are LDAP
> servers, mail servers,.....
> To ensure high availability I have to use something like round robin in DNS
> (most of the clients, e.g. LDAP clients can be configured to search only one
> LDAP server)
> The problem with DNS round robins is that they make no attempt to prioritize
> DNS results (e.g. based on network location)
> Is there anyway so I can make DNS return first hosts on the local network,
> before trying hosts that are farther away.

Check out the "sortlist" option. Unfortunately, caching servers and slaves
which are not configured with the same sortlists will interfere with the sort
order when they give out answers for the names. If you control all of the
caching servers and slaves, this shouldn't be a problem. If you control all of
the slaves but not all of the caching servers, another quasi-solution is to
lower TTL's on the records in order to defeat caching, but this will increase
DNS traffic.


- Kevin