Hi Dominick,

more below

On 10/17/19 3:41 AM, Dominick C. Pastore wrote:

I'm having a bit of a problem with the "cname" option in Dnsmasq. I have some configuration options 
like these in dnsmasq.conf, where "host1" and "host2" have IPv4 addresses from DHCP:


This works well for A lookups on git.example.com and nas.example.com, but the 
cname options are ignored for AAAA lookups. I think this is by design, since 
the man page says the target of a cname must be known or it will be ignored. 
(Although, maybe this is unintentional in this case? It does seem like a bit of 
a bug for a name to *sometimes* be a CNAME, depending on the request type.) 
Unfortunately, it's causing problems when the AAAA queries are forwarded 
upstream, but I'm not sure how to fix it since these servers don't have IPv6 

For some background:

The goal is to provide something like split-horizon DNS. Host1 and host2 reside 
behind NAT. On public DNS, philadelphia.example.com resolves to their public 
address, with git.example.com and nas.example.com both being CNAMEs to that 
name. But within the LAN, git.example.com and nas.example.com should be CNAMEs 
to their local names.
Is there any reason you want CNAME used? I think they unnecessary complicate the setup without obvious advantage. Just provide directly either local or public addresses for those names. Why is CNAME used?

The problem is, some clients cache their DNS requests. When these clients send 
a AAAA request, it gets forwarded upstream and they end up caching the public 
CNAME record. Then, they use the (incorrect) cached CNAME for A requests, too.

Is there a good way to solve this?
Just make sure client's DNS cache is flushed after connection type change. That is important for split-horizon.


Dnsmasq-discuss mailing list

Petr Menšík
Software Engineer
Red Hat, http://www.redhat.com/
email: pemen...@redhat.com  PGP: 65C6C973

Dnsmasq-discuss mailing list

Reply via email to