CompTIA Server+ (SK0-005)TroubleshootingMedium
A technician is troubleshooting a newly installed Linux server that can resolve external domain names (e.g., google.com) but cannot access internal resources by their hostname (e.g., internalapp.local). Pinging internal IP addresses works correctly. Which of the following is the MOST likely misconfiguration?
- AIncorrect default gateway
- BDuplex mismatch on the network interface
- CMissing or incorrect DNS server entry
- DFirewall blocking outbound connections
Show answer & explanationAnswer & explanation
Correct answer: C. Missing or incorrect DNS server entry
The ability to resolve external names but not internal hostnames, while IP-based communication works, indicates an issue with resolving internal names. This is typically due to a missing or incorrect entry for the internal DNS server responsible for the 'internalapp.local' domain.
Why the other options are wrong
- A. An incorrect default gateway would prevent all external communication, which is not the case here.
- B. A duplex mismatch would cause general network performance issues and packet loss, not selective hostname resolution problems.
- D. A firewall blocking outbound connections would prevent all communication, or specific ports, but wouldn't differentiate between internal and external name resolution if IP works.
DNS Resolution for Internal Resources
Internal DNS resolution relies on correctly configured DNS server entries that can resolve hostnames within a private network, often using specific internal DNS servers.
- External domains resolved by public DNS servers.
- Internal hostnames resolved by private/internal DNS servers.
- '/etc/resolv.conf' on Linux specifies DNS servers.
- Problematic if internal DNS server is missing or unreachable.
Memory trick: Linux networking is like a well-oiled machine, but DNS is the address book.