CompTIA Network+ (N10-009)Network OperationsMedium
Users on VLAN 30 report that newly connected laptops cannot obtain IP addresses, while devices already on the network keep functioning normally. The DHCP server logs show repeated 'no addresses available' errors for the /24 scope, which uses an 8-day lease time. Without immediately redesigning the IP addressing scheme, what should the administrator do first to relieve the address shortage?
- AConfigure static IP addresses on every new device joining the network
- BEnable DHCP snooping on all access layer switches
- CDecrease the DHCP lease time so addresses are returned to the pool more quickly
- DChange the subnet mask from /24 to /23 without updating the DHCP scope
Show answer & explanationAnswer & explanation
Correct answer: C. Decrease the DHCP lease time so addresses are returned to the pool more quickly
Reducing the lease time causes expired leases to be reclaimed and reissued more frequently, quickly freeing addresses for new devices without any re-addressing project. Expanding the subnet (option D) would require re-addressing and coordination, making it a longer-term fix, not an immediate one.
Why the other options are wrong
- A. Static addressing on every device is not scalable and doesn't fix the shared pool shortage.
- B. DHCP snooping prevents rogue DHCP servers; it has no effect on address pool size.
- D. Changing the mask without updating the DHCP scope config wouldn't add usable addresses to the pool.
DHCP Scope Exhaustion
A condition where all addresses in a DHCP pool are leased out, preventing new clients from receiving an IP address.
- Common on VLANs with many transient devices (guest Wi-Fi, BYOD)
- Shortening lease time speeds address reclamation
- Long-term fix may require expanding the scope or subnet
Memory trick: Short leases, quick releases.