My Macbook is connected to my router, running OpenWrt. In that router, I have defined a static host, pointing to a local IP address. Lets call it service.example.com, with IP 10.0.0.10. In public DNS, service.example.com is a CNAME of my dynamic DNS hostname which currently is not being updated due to the router being behind carrier grade NAT, hence the need to define the host name as a static host in my router.
This works. Sometimes.
Sometimes my Mac can't connect to service.example.com, because for some obscure reason it has decided that it will disregard the response of my local DNS server, and use something else. If I reset mDNSresponder's cache by sending a SIGHUP, it'll work again for an indeterminate amount of time.
I would like to figure out where mDNSresponder gets the wrong IP from. Dumping the cache is not possible: "XPC service returns error, description: State dump is only enabled in internal builds".