The error "Can't find 22.78.224.10.in-addr.arpa.: No answer" indicates that a reverse DNS lookup failed because the authoritative nameservers for the IP address range do not have a PTR record configured, or the local resolver is misconfigured. This typically happens when querying an IP address that lacks proper reverse DNS delegation from its ISP or cloud provider. To resolve this, you must verify if the record exists globally using public DNS tools and then check your local system's resolver configuration to ensure it is querying the correct servers.
Understanding Reverse DNS Lookup Errors
When you run a command like
nslookup 22.78.224.10, the tool attempts to perform a reverse DNS (rDNS) lookup. It converts the IP address into a format suitable for DNS queries, resulting in the hostname
10.224.78.22.in-addr.arpa. The system then queries the Domain Name System to find a Pointer (PTR) record associated with this name. A PTR record maps an IP address back to a domain name, which is the opposite of the standard A or AAAA record that maps a name to an IP.
The specific error message "No answer" means that the query reached the authoritative nameservers for that IP block, but those servers returned no data. This is distinct from "NXDOMAIN," which implies the name does not exist at all, or "SERVFAIL," which suggests a technical issue with the server itself. In this context, "No answer" usually signifies that the owner of the IP range has simply not created a PTR record for this specific address. This is common with dynamic IPs, certain cloud hosting environments, or newly assigned blocks where reverse DNS setup was overlooked.
If you are experiencing broader connectivity issues alongside this DNS error, you might want to review our guide on
Troubleshooting: Cannot Connect to the Internet to rule out general network stack problems.
Verifying Global DNS Records
Before modifying your local system, confirm whether the PTR record exists anywhere in the global DNS. Use the
dig command with the
-x flag, which automatically handles the reverse conversion of the IP address.
dig -x 22.78.224.10 +short
If the output is empty, it confirms that no PTR record exists for this IP in the global DNS hierarchy. You can also try querying specific public resolvers to see if they cache stale data or provide different results. For example:
dig -x 22.78.224.10 @8.8.8.8 +short
dig -x 22.78.224.10 @1.1.1.1 +short
If these commands return empty strings, the issue is not with your local machine but with the lack of configuration by the entity controlling the IP address. In such cases, you cannot fix the reverse DNS locally; you must contact the ISP or hosting provider responsible for the
22.78.224.0/24 subnet and request they add the PTR record pointing to the desired hostname.
Checking Local Resolver Configuration
Even if a record existed, your local system might fail to resolve it due to misconfiguration. On Linux systems, the resolver settings are typically managed through
/etc/resolv.conf or via NetworkManager. Check your current DNS servers by viewing the configuration file:
cat /etc/resolv.conf
Ensure that the
nameserver entries point to reliable DNS servers. If you are using a local caching daemon like
systemd-resolved or
dnsmasq, verify its status. Sometimes, local firewall rules or strict security policies may block outbound UDP port 53 traffic, preventing DNS queries from leaving the host. Although rare for simple lookups, testing connectivity to port 53 on your configured DNS servers can help isolate this.
For users running virtual machines, especially in NAT modes, DNS resolution issues often stem from the guest OS not inheriting the host's DNS settings correctly. If you are working within a virtualized environment, consider checking our article on
VMWare 17 Player Linux NAT guest can ping but cannot resolve DNS names for specific fixes related to virtual network adapters.
Diagnosing Temporary Failures
In some scenarios, the error might be intermittent. If you receive a "Temporary failure in name resolution" instead of "No answer," the issue is likely transient. This could be due to network congestion, DNS server overload, or DHCP lease renewals. Use
resolvectl on modern systemd-based distributions to get detailed status information about your network interfaces and their associated DNS servers.
resolvectl status
Look for any flags indicating failures or timeouts. If you suspect your system is stuck with old DNS cache entries, flushing the cache can help. For
systemd-resolved, use:
sudo resolvectl flush-caches
This forces the system to re-query the DNS servers for all subsequent requests, ensuring you are getting fresh data.
Conclusion
The "No answer" error for reverse DNS lookups is primarily a data availability issue rather than a client-side error. Most often, the IP address in question simply does not have a PTR record set up by its provider. Your first step should always be to verify this using public tools like
dig. If the record is missing globally, contact your hosting provider. If the record exists but your system fails to resolve it, investigate your local
/etc/resolv.conf settings, firewall rules, and caching services. Properly diagnosing the source of the failure ensures you apply the correct fix without unnecessary configuration changes.
Frequently Asked Questions
What is the difference between NXDOMAIN and No Answer?
NXDOMAIN means the domain name queried does not exist in the DNS zone, while No Answer means the query reached the authoritative servers but received no response data. In reverse DNS, No Answer usually implies the IP block exists but lacks a PTR record for the specific address.
Can I create a PTR record for my own IP address?
No, you cannot create a PTR record directly. PTR records are controlled by the organization that owns the IP address range (the ISP or cloud provider). You must request them to add the record pointing to your domain name.
Why does nslookup work for forward lookups but fail for reverse?
Forward lookups (name to IP) are commonly configured for websites and services. Reverse lookups (IP to name) are optional and often neglected by providers, especially for dynamic or consumer-grade IP addresses. This asymmetry is why forward lookups succeed while reverse lookups fail.
How do I check if my firewall is blocking DNS?
You can test DNS connectivity by attempting to reach port 53 on your DNS server using
nc or
telnet. For example,
nc -zv 8.8.8.8 53 will tell you if the connection is allowed. If it times out, your firewall is likely blocking outbound DNS traffic.
Does clearing the DNS cache fix reverse lookup errors?
Clearing the cache only helps if the error is due to stale or corrupted cached data. If the global DNS truly lacks a PTR record, clearing the cache will not make the record appear. It is useful for troubleshooting temporary failures but not for missing records.