[Dnsmasq-discuss] Sync DNS servers in a VPN connected network

mike@farmwald.com mike at pmfarmwald.com
Sat May 12 00:10:14 BST 2018


I have a home network (call it 10.2.0.0/16) and multiple VPN connected
networks (10.x.0.0/16).
I would like each of the 10.x networks to have a separate dnsmasq, with
their own DHCP and DNS server.
However I'd like the 10.2 DNS server to hold DNS information for all of
the networks. Thus I could first check the local (10.x) and then the home
(10.2) DNS, ensuring I get information for all devices, no matter where
the host is.
I can't see an easy way to do this, but maybe I'm missing something.
I have a proposal that seems simple. If the 10.x dnsmasq servers had a
mechanism for forwarding DHCP requests/renewals as advisory only to
upstream dnsmasq servers, and then the upstream servers would simply
remember the bindings in the relevant DNS database, I'm pretty sure my
problem would be solved.
I would be fine with UDP advisory messages, as if some updates get lost
there will be later updates to keep the upstream  DNS database in good
shape.
This is somewhat similar to the "--dhcp-script" option, but I need every
request/renewals to be forwarded, and I need dnsmasq to accept such
advisory requests.
I envision something like "--send-advisory-updates=<ip addr>" to cause
dnsmasq to start sending advisory updates, and the dns server would need
to be able to handle these update requests.



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