Configuration error: It may be caused by domain name resolution configuration error resulting in inability to resolve. Check if the domain name resolution configuration file (such as /etc/resolv.conf) is correctly set with DNS server information.
If the DNS server malfunctions, CentOS 7 will be unable to resolve domain names. Check the status of the DNS server and try connecting to other available DNS servers.
Network connection issue: If the network connection is unstable or having problems, it may lead to domain resolution failure. Check if the network connection is normal, including network configuration, network card settings, routing table, etc.
Firewall blockage: Firewalls may block traffic of domain name resolution requests. Check firewall settings and ensure that DNS requests are allowed to pass through.
Domain server records error: Domain server records may contain errors, resulting in failed domain resolution. Check if domain server records are correctly configured.
DNS cache issue: DNS cache may expire or become corrupted, leading to domain resolution failure. Try clearing the DNS cache and resolving the domain again.
