There's no record returned in the answer of a negative response, so there's no Time to Live (TTL) value compared to a positive response. The resolver previously received this query and had it cached, so it returned the response from the cache. After the user created the new record, they made the query again. If negative caching is turned ON in their resolver settings, the resolver caches this response. When the user made a query to before creating the new record, they received an NXDOMAIN response. The user continues to receive an NXDOMAIN response while users in other networks can successfully resolve the record. This user also owns, so they create a new record for. ![]() The reason for this response is that the record doesn't exist. Consider the following example:Ī client makes a DNS query for and receives a response code of NXDOMAIN. An NXDOMAIN response is considered a negative response. Negative caching is the process of storing a negative response from an authoritative name server in the cache. Determine if your issue is the result of negative caching If there's a rule that matches the domain name, then the query for the domain is routed to the configured target IP addresses instead of the default public resolvers. When using only resolver rules and no private hosted zone:Ĭheck the Route 53 resolver rules. The VPC DNS doesn't fall back on the public hosted zone if the record isn't present in the private hosted zone. Clients in the VPC can't resolve a record that was created in the public hosted zone. For example, you might have both a private hosted zone and a public hosted zone for the domain associated with a VPC. When using a private hosted zone and no resolver rule:Ĭheck if there's a private hosted zone with matching domain names associated with the VPC. In this case, the DNS query is sent to the target IP address configured as the target in the resolver rule. For more information, see Considerations when working with a private hosted zone. If the resolver rule and private hosted zone domain name overlap, the resolver rule takes precedence. ![]() When using resolver rules and private hosted zones: If you're using the VPC DNS resolver, then check the private hosted zones and Route 53 resolver rules. If you don't see the VPC DNS resolver in /etc/nf, then check the custom DNS resolver.Ģ. For example, if the VPC CIDR is 10.0.0.0/8, then the DNS resolver IP address should be 10.0.0.2. ![]() Look for the default VPC DNS resolver (which is the VPC CIDR+2). For Windows, check the DNS servers in the ipconfig /all output. Check the resolver IP address configured on the client operating system (OS). This should make it easier to diagnose these sorts of issues. Note that OpenShift 4.10 adds an API to make it easier to increase CoreDNS's logging verbosity cf. Could you check the "coredns_forward_responses_total" metric to see whether the "forward" plugin is reporting SERVFAIL responses? I could be mistaken, but I don't believe this is the case as far as I can tell, the only cases in which CoreDNS's "forward" plugin returns a SERVFAIL response are if no upstream resolver can be reached or an upstream resolver returns a SERVFAIL response, and the only case in which CoreDNS's "kubernetes" plugin returns a SERVFAIL response is if CoreDNS hasn't synched with the Kubernetes API (which should only need to happen once when CoreDNS starts). Due to priorities and lack of capacity, we have still not been able to engage on this issue.īased on comment 25, it seems that at least in some cases the alert is legitimate, and that the application is sending spurious requests that elicit SERVFAIL responses from the upstream resolver.Ĭomment 21 asks whether CoreDNS could be reporting NXDOMAIN errors as SERVFAIL errors.
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