CompTIA A+ Core 1 (220-1201)NetworkingMedium
A network administrator wants to allow internal client workstations to resolve external domain names to IP addresses. Which TCP/UDP port must be open on the firewall for this traffic to succeed?
- A389
- B53
- C67
- D443
Show answer & explanationAnswer & explanation
Correct answer: B. 53
DNS (Domain Name System) uses port 53 for both TCP and UDP to resolve domain names to IP addresses. Port 67 is DHCP, 389 is LDAP, and 443 is HTTPS.
Why the other options are wrong
- A. Port 389 is used by LDAP for directory service queries.
- C. Port 67 is used by DHCP servers for address assignment, not name resolution.
- D. Port 443 is used for encrypted HTTPS web traffic, not DNS.
DNS Port 53
DNS uses port 53 (UDP for queries, TCP for zone transfers/large responses) to translate domain names into IP addresses.
- UDP 53 for standard lookups
- TCP 53 for zone transfers or large replies
- Essential for resolving domain names to IPs
Memory trick: '53 keys' unlock the name-to-number door.