[Dnsmasq-discuss] Is there an "all-servers" parameter for downstream servers?

[Alberto Cuesta-Canada]

Hi all,
 
Is there an "all-servers" parameter for downstream servers?
 
I have a configuration with three DNS domains, each one served by two dnsmasq servers (complete description at the end).
 
I'm trying to set up a redundant structure, with cron jobs that ensure that both DNS servers for each domain are identical, so if one fails, the other will serve the requests. All the machines under my control repeat the query in rapid sucession if it doesn't come immediately answered, and the DNS servers seem to understand that so the behaviour is that any query from a machine in my domain reaches all dns servers in the network and it is always answered, regardless of which machines are down. For the size of my systems this is fine, it doesn't matter if it is unefficient.
 
The problem I have is that the corporate servers don't work that way. We have three of them, and when a machine outside my domains makes a query, all of them are queried and route to one of my main servers. Unfortunately they always ask to the first one, and never repeat the query. The round-robin protocol seems to reset for each query, so my main servers only ask the primary servers downstream, fail, and the corporate servers return (and cache) a failure, thus rendering my failover structure useless for other domains. 
 
This could be solved modifying the configuration on the corporate server (politics!), or instructing the my main dns servers to always route queries to all servers downstream, and to serve the first result coming up. It's the same as using "all-servers", but downstream.
 
Here is a small diagram (use monospace to see it):
 
                        CORPORATE    172.30.0.1    (corporate.local)
                                     172.30.0.2
                                     172.30.1.1
                                         ||
                                         || *.mydomain.local
                                         ||
                           MAIN    192.168.0.250    (main.mydomain.local)
                                   192.168.0.251
                                    ||       ||
                sub1.mydomain.local ||       || sub2.mydomain.local
                                    ||       ||
                  SUB1    192.168.1.250     192.168.2.250    SUB2
                          192.168.1.251     192.168.2.251
 
server=/sub1.mydomain.local/192.168.1.250
server=/sub1.mydomain.local/192.168.1.251
server=/sub2.mydomain.local/192.168.2.250
server=/sub2.mydomain.local/192.168.2.251
   
Many thanks,
 
Alberto Cuesta-Canada
GaaS Team Lead
Excelian Ltd.
+44 (0) 7942633361

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