Tutorials · Routing & Internet
How to Configure DHCP Scopes, Reservations and Options
Hand out addresses reliably: one scope per VLAN, reservations for printers and cameras, the right DNS and gateway options and sensible lease times.
Before you start
- A gateway, Layer 3 switch or server acting as DHCP server
- Your IP plan (see the subnet-planning tutorial)
Step by step
Create one scope per VLAN
Each VLAN needs its own range, gateway and DNS. Exclude addresses used by static devices.
ip dhcp excluded-address 10.10.0.1 10.10.0.20 ip dhcp pool STAFF network 10.10.0.0 255.255.255.0 default-router 10.10.0.1 dns-server 10.99.0.53 1.1.1.1 lease 1
Set lease times by use
Office VLANs: 1 day. Guest Wi-Fi: 1–4 hours so addresses are recycled quickly. Servers and cameras: reservations or static IPs.
Create reservations
Bind a MAC address to an IP for printers, cameras and access points so they always get the same address.
Add useful options
Option 42 (NTP), option 66/150 (TFTP for IP phones) and option 43 (controller discovery for access points) save manual configuration.
Relay across VLANs
If one central server serves many VLANs, configure DHCP relay on each Layer 3 interface (see the inter-VLAN tutorial).
Protect DHCP
Enable DHCP snooping so rogue DHCP servers cannot hand out fake gateways.
Monitor utilisation
Alert when a scope is over 80% used, especially guest Wi-Fi.
Commands are generic, industry-standard examples. Exact syntax and menu names vary by model and firmware; check your device's manual on the Documentation page.
Pro tips
- Never run two DHCP servers on the same VLAN without coordination.
- Size guest scopes generously; phones change MAC addresses for privacy.
FAQ
Frequently asked questions
Why do clients get 169.254.x.x addresses?
They could not reach a DHCP server. Check the VLAN, relay and scope availability.
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Ask Navijin technical support or an authorised partner for help with your configuration.