How to make the DNS resilient

binddomain-name-system

I'm a Sysadmin and am responsible for our external DNS servers. We're trying to make our DNS more resilient.

We have our own DNS servers (Bind). We have one running on each of our two ISP's.

Their IP's are public IP's on the internet, and one is configured as a master, as one as a slave (this is all working).

The question I have.. when one of our ISP's goes down, we tend to lose DNS completely. From what we can tell, this is because our TLD DNS servers are issuing both nameserver's IP's even though one is down.

How do we get around this?

Best Answer

Your parent domain will always keep dishing out all of your name server addresses, that's by design.

The real question is why you apparently are losing DNS when one of the ISPs goes down. That shouldn't happen. Whilst you should expect to see some delays resolving domain names when that happens it shouldn't actually stop working altogether.

Can you provide more information? What do you actually mean by "losing DNS completely"?

Related Solutions

DNS Best Practices – Top Level Domain/Domain Suffix for Private Network

Since the previous answers to this question were written, there have been a couple of RFCs that alter the guidance somewhat. RFC 6761 discusses special-use domain names without providing specific guidance for private networks. RFC 6762 still recommends not using unregistered TLDs, but also acknowledges that there are cases where it will be done anyway. Since the commonly used .local conflicts with Multicast DNS (the main topic of the RFC), Appendix G. Private DNS Namespaces recommends the following TLDs:

intranet
internal
private
corp
home
lan

IANA appears to recognize both RFCs but does not (currently) incorporate the names listed in Appendix G.

In other words: you shouldn't do it. But when you decide to do it anyway, use one of the above names.

Way to batch create DNS slave zones on a new slave DNS server

Writing a script to do this shouldn't take very long, especially if you name the zone files after the domain.

ls master.dir > domain.list

foreach domain (`cat domain.list`)
echo 'zone "$domain" { type slave; file "slave/$domain"; masters { 1.2.3.4 }; };' >> named.conf.slaves
end

And add include named.conf.slaves; to your named.conf

Best Answer

Related Solutions

DNS Best Practices – Top Level Domain/Domain Suffix for Private Network

Way to batch create DNS slave zones on a new slave DNS server

Related Topic