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Difficulty: HardTroubleshooting IP Addressing and DHCP Services

Users on a corporate subnet (10.20.4.0/2410.20.4.0/24) intermittently experience network connectivity loss accompanied by IP address conflict warnings. A network technician discovers that a new network printer was manually configured with the static IP address 10.20.4.1510.20.4.15. The local DHCP server scope is configured for 10.20.4.1/2410.20.4.1/24 with a distribution pool ranging from 10.20.4.1010.20.4.10 through 10.20.4.25410.20.4.254. Which of the following actions on the DHCP server is the best resolution to permanently prevent this conflict?

  1. Configure an exclusion range on the DHCP scope for the static IP address assigned to the printer.Answer
  2. B
    Enable a DHCP relay agent on the local router interface to filter duplicate address broadcast requests.
  3. C
    Configure the DHCP scope's Default Gateway (Option 003) to use the static printer address of 10.20.4.1510.20.4.15.
  4. D
    Instruct affected client workstations to fall back to APIPA (169.254.x.x) addresses when an IP collision occurs.

Answer

Configure an exclusion range on the DHCP scope for the static IP address assigned to the printer.
The issue is caused by overlapping address allocations: the static IP address (10.20.4.1510.20.4.15) assigned to the printer lies within the DHCP scope's active lease pool (10.20.4.1010.20.4.10–10.20.4.25410.20.4.254). Creating an exclusion range for 10.20.4.1510.20.4.15 on the DHCP server prevents the server from issuing that address to dynamic clients, eliminating duplicate IP address collisions.

Step-by-Step Solution

1
Identify the root cause of the IP address conflict
The static IP address (10.20.4.1510.20.4.15) falls inside the active DHCP distribution pool range (10.20.4.1010.20.4.10 to 10.20.4.25410.20.4.254).
When a dynamic client requests an IP address, the DHCP server may lease 10.20.4.1510.20.4.15, causing two devices to claim the same IP.
2
Determine the appropriate DHCP server administrative action
Create an exclusion entry on the DHCP server scope specifically omitting 10.20.4.1510.20.4.15 (or a block containing it).
Exclusions guarantee the DHCP server will never lease specified addresses to dynamic clients while keeping them within the defined subnet scope.

Key Concept

DHCP Scope Exclusions and Static Address Management
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Topics

Troubleshooting IP Addressing and DHCP Services

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