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Difficulty: Very hardTroubleshooting IP Addressing and DHCP Services

A network administrator is troubleshooting connectivity failures for dynamic clients in a newly provisioned branch office. Users on VLAN 102 (10.102.4.0/2210.102.4.0/22) report that their workstations periodically lose connection to local corporate resources and display IP addresses in the 169.254.x.x169.254.x.x range. The centralized dual DHCP redundant servers reside on VLAN 10 (10.10.1.510.10.1.5 and 10.10.1.610.10.1.6).

Upon reviewing the Core L3 Switch configuration and DHCP server diagnostics, the administrator notes the following:
text Interface VLAN 102 description Workstation_Subnet ip address 10.102.4.1 255.255.252.0 ip helper-address 10.10.1.5 ! DHCP Server Scope Statistics (10.102.4.0/22): Active Leases: 1022 / 1022 (100% Utilized) Default Lease Time: 8 Days Environment Type: High-density roaming laptop conference area

Which of the following actions should the network administrator perform to resolve the IP address assignment failures and ensure high-availability DHCP relay operations? (Select TWO.)

  1. Add a second `ip helper-address 10.10.1.6` command under the Interface VLAN 102 configuration on the Core L3 Switch.Answer
  2. Decrease the DHCP lease duration on the server scope and implement shorter lease periods suited for transient device environments.Answer
  3. C
    Configure the client default gateway statically to 169.254.0.1 to permit APIPA addresses to route across Layer 3 interfaces.
  4. D
    Change the subnet mask on Interface VLAN 102 from 255.255.252.0 to 255.255.255.0 to expand the total usable host capacity of the DHCP pool.

Answer

The network administrator must add the second DHCP relay address (`ip helper-address 10.10.1.6`) on the VLAN subinterface for relay redundancy, and reduce the DHCP scope lease duration on the DHCP server to mitigate scope exhaustion caused by transient devices.
The scenario highlights two distinct IP addressing and DHCP troubleshooting issues: scope exhaustion and missing relay redundancy. First, reducing the lease duration allows transient client leases to expire rapidly, recycling addresses back into the pool. Second, configuring the secondary IP helper address (`ip helper-address 10.10.1.6`) on the Layer 3 interface allows the router to forward DHCP unicast requests to both redundant DHCP servers simultaneously.

Step-by-Step Solution

1
Analyze client IP output and DHCP scope state
Workstations receive 169.254.x.x169.254.x.x (APIPA) because the single configured DHCP server's scope is 100% exhausted (1022/10221022/1022 active leases).
An 8-day lease duration in a transient conference environment retains IP assignments long after devices disconnect, leading to exhaustion.
2
Evaluate DHCP Relay (IP Helper) configuration for redundancy
The Layer 3 interface only contains `ip helper-address 10.10.1.5`, omitting the secondary server (10.10.1.610.10.1.6).
Without configuring the second helper address, relay requests are never forwarded to the backup server when the primary server scope is exhausted or unavailable.
3
Select appropriate remediation steps
Adding `ip helper-address 10.10.1.6` ensures dual-relay forwarding, while shortening lease times frees expired leases quickly.
Both steps together resolve immediate capacity bottlenecks and build resilient DHCP relay operations across subnets.

Key Concept

Troubleshooting DHCP Scope Exhaustion and Redundant Relay Agent Placement
Estimated Time:3m 0s
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Topics

Troubleshooting IP Addressing and DHCP Services

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