DHCP scope has leases available but clients self-assign

Scenario

Clients on a VLAN are falling back to APIPA addresses even though the DHCP scope has room.

Recommended Resolution Path

1. Check helper addresses or relay configuration on the L3 interface.
2. Validate that the DHCP server is authorized and listening on the expected interface.
3. Use a packet capture to see whether DISCOVER packets reach the server and whether OFFER packets return.
4. Exclude switch port ACLs or NAC rules that may block the exchange.

Technician Notes

Confirm the business impact, document the root cause, and capture any preventative follow-up in the PSA or client knowledge base.