Overview
Sometimes you want a device to always receive the same IP address, but still benefit from central management. DHCP reservations provide exactly that — a fixed address delivered through DHCP. This lesson explains reservations and when to use them.
Learning objectives
- Define a DHCP reservation.
- Distinguish reservations from dynamic leases and manual static IPs.
- Identify when reservations are appropriate.
Core concept
A DHCP reservation binds a specific IP address to a particular device (identified by its MAC address) within the DHCP server. The device still uses the normal DHCP process, but the server always offers it the same reserved address. This gives the device a stable IP while keeping its configuration centrally managed by the DHCP server.
Compare three approaches:
- Dynamic lease — any available address from the pool; may change over time.
- Reservation — a consistent address for a known device, delivered via DHCP.
- Manual static — configured on the device itself, independent of DHCP.
How it works
The administrator creates a reservation by associating a device's MAC address with a chosen IP in the DHCP server's configuration (usually an address set aside from the dynamic pool). When that device sends its DHCP Request, the server recognizes its MAC and always returns the reserved address. Change the device's other settings (gateway, DNS) centrally, and it still receives updates through DHCP — the address just never changes.
Practical example
A network printer needs a fixed address so everyone's print settings keep working, but you would rather not configure it by hand on the device. You add a DHCP reservation binding the printer's MAC to 192.168.1.20. From then on the printer always gets 192.168.1.20 from DHCP, and if you later change the DNS servers for the network, the printer picks up the change automatically like any other DHCP client.
Cybersecurity relevance
Reservations aid inventory and control: stable, known addresses for servers, printers, and infrastructure make monitoring and firewall rules easier and more reliable. However, reservations key on MAC address, which can be spoofed, so they are a convenience and organizational aid, not a security boundary on their own. Analysts treat MAC-based identity as weak authentication and layer stronger controls where security matters.
Common mistakes
- Confusing a reservation with a manual static IP — a reservation is still delivered by DHCP and centrally managed.
- Reserving an address inside the active dynamic pool, risking conflicts (reservations usually sit outside the pool range).
- Treating MAC-based reservations as security — MACs can be spoofed.
Key takeaways
- A DHCP reservation always assigns the same IP to a specific device (by MAC), delivered through DHCP.
- It combines a stable address with central management, unlike a plain dynamic lease or a device-side manual static IP.
- Reservations are ideal for printers, servers, and infrastructure, but MAC identity is spoofable and not a security control by itself.
Check your understanding
- How does a DHCP reservation differ from configuring a static IP directly on the device?
- Why should a reserved address generally sit outside the dynamic address pool?