After a new firewall is installed, users report that they do not have connectivity to the Internet. The output of the ipconfig command shows an IP address of 169.254.0.101. Which of the following…

The correct answer is B. UDP 67 C. UDP 68. The 169.254.x.x address is an APIPA (Automatic Private IP Addressing) address, which means the client failed to receive a response from a DHCP server. DHCP uses UDP exclusively - UDP port 67 for the DHCP server (receiving client broadcasts) and UDP port 68 for the DHCP client…

Network troubleshooting

Question

After a new firewall is installed, users report that they do not have connectivity to the Internet. The output of the ipconfig command shows an IP address of 169.254.0.101. Which of the following ports would need to be opened on the firewall to allow the users to obtain an IP address? (Select TWO).

Options

AUDP 53
BUDP 67
CUDP 68
DTCP 53
ETCP 67
FTCP 68

How the community answered

(30 responses)

A
3% (1)
B
83% (25)
E
3% (1)
F
10% (3)

Explanation

The 169.254.x.x address is an APIPA (Automatic Private IP Addressing) address, which means the client failed to receive a response from a DHCP server. DHCP uses UDP exclusively - UDP port 67 for the DHCP server (receiving client broadcasts) and UDP port 68 for the DHCP client (receiving server responses). Both ports must be open on the firewall so that DHCP Discover/Offer/Request/Acknowledge messages can flow between clients and the DHCP server. TCP 53 and UDP 53 are for DNS; TCP 67/68 are not used by DHCP.

Topics

#DHCP#firewall ports#UDP 67/68#APIPA

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