[CentOS] how to increase DNS reliability?

[Warren Young]

On Jul 25, 2019, at 5:42 PM, Nataraj <incoming-centos at rjl.com> wrote:
> 
> On 7/25/19 4:31 PM, Nataraj wrote:
>> It doesn't really help those clients I can not run name servers on,
>> though.
> 
> Another alternative is to look at the multicast dns (mdns) protocol.

That’s for allowing a device to self-advertise its own name, along with other things, like available services.  If you have such devices, then configuring the other machines on the network to pay attention to such advertisements allows them to see the new names and services when they appear.

…And much more importantly, when they *disappear*, since many ZeroConf/Bonjour/Avahi/mDNS speaking devices are mobile and aren’t always available.

This protocol is one common way for network printers to advertise their services, for example.  (The other common way is SMB/CIFS.)

> I'm pretty sure it's inplemented in avahi daemon

Yes, that’s an implementation of mDNS for POSIX type systems.  

> If your client supports
> it then I would think that all you have to do is enable it.

I’m not sure how this is relevant here.  For mDNS to be the solution to the OP’s problems, he’d have to also have mDNS multicasts going out advertising services, so the Avahi daemon would have something to offer when a compatible program comes along looking for services to connect to.

I suppose you could use mDNS in datacenter type environments, but it’s a long way away from the protocol’s original intent.

You could imagine a load balancer that paid attention to mDNS advertisements to decide who’s available at the moment.  But I don’t know of any such implementation.