SK0-004 · Question #19
Clients cannot connect to the network. A technician determines that port 68 is not open. Which of the following protocols is being blocked?
The correct answer is D. DHCP. Port 68 is the well-known UDP port used by DHCP clients to receive IP configuration from a server. Blocking port 68 prevents clients from completing the DHCP handshake and obtaining an address.
Question
Clients cannot connect to the network. A technician determines that port 68 is not open. Which of the following protocols is being blocked?
Options
- APOP3
- BDNS
- CLDAP
- DDHCP
How the community answered
(50 responses)- A6% (3)
- B2% (1)
- C4% (2)
- D88% (44)
Why each option
Port 68 is the well-known UDP port used by DHCP clients to receive IP configuration from a server. Blocking port 68 prevents clients from completing the DHCP handshake and obtaining an address.
POP3 (Post Office Protocol v3) operates on port 110 for email retrieval and has no association with port 68.
DNS operates on port 53 (UDP and TCP) for name resolution queries and has no association with port 68.
LDAP operates on port 389 for directory service queries and has no association with port 68.
DHCP uses UDP port 67 on the server side and UDP port 68 on the client side; when port 68 is blocked, clients cannot receive DHCPOFFER or DHCPACK packets, which prevents IP address assignment and network connectivity entirely.
Concept tested: DHCP port assignments and client IP acquisition
Source: https://www.rfc-editor.org/rfc/rfc2131
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