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Use a DHCP reservation for an office printer or scanner that supports DHCP and needs a steady address. Set a manual static address when the device must keep its network settings independently of DHCP or its vendor requires it. Both choices can give the device a predictable internal IP address. A public static IP from your internet provider is a separate setting that applies to the connection outside your office.
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Three ways devices get an address
| Method | Where the address comes from | When it fits |
|---|---|---|
| Ordinary DHCP lease | The DHCP service assigns an address from the available pool | Laptops, phones and devices whose address does not need to stay fixed |
| DHCP reservation | The DHCP service assigns a specific address to the matching device identifier | A printer or scanner that needs a stable address and supports DHCP |
| Manual static address | Someone sets the address and network settings on the device | Equipment that needs a fixed address even when DHCP is unavailable or whose vendor requires manual settings |
How reservations work during a device or router replacement
A lease is an address the DHCP server lends to a device for a period of time. The scope is the address range and network settings the server manages for that subnet. With a reservation, the server recognizes the device by its client identifier and offers the assigned address when the device asks. For a copier, the identifier is often based on the network adapter’s MAC address. That lets the office manage the assignment in one place. Replacing the printer can change the identifier, and switching between wired and wireless interfaces can do the same. Moving to a new router may also mean moving the reservations if the router provides DHCP.
What happens during a router or switch replacement
An office might replace a router that was also the DHCP server. The network name and internet connection may look familiar, but the new router may use a different subnet or lack the old reservations. A laptop can obtain new settings and keep working while a copier with a manually configured address stays on the old subnet. Verify which device now hands out addresses and compare the old and new address plans before reconnecting the whole office.
If two DHCP servers unexpectedly answer on the same network, some devices can receive different settings than their neighbors. A technician can check which server provided a lease and whether the gateway or DNS differs between working and failing machines. A failed print job by itself is insufficient evidence to turn off a DHCP service.
Where address conflicts come from
A conflict can happen when a device is manually set to an address that DHCP is free to give to someone else. Symptoms can be intermittent because the two devices only compete when they are both active. Manual addresses should be tracked and kept clear of addresses the DHCP service can lease to other clients. Write down which subnet or VLAN the address belongs to. The same room or switch can serve several networks with different rules.
Diagnose a copier that stopped printing
Say the office print queue sends jobs to 192.168.20.45. The old copier was reserved at that address. The replacement copier’s network settings show 192.168.20.83, and the DHCP server still has .45 tied to the old device. The replacement can connect to the network, but jobs are still going to .45.
With the old copier disconnected, IT checks that .45 is available and updates the reservation for the replacement’s network adapter. After the copier renews its lease, its settings page should show 192.168.20.45 again. The print queue already points there, so send a test job from a normal employee computer. If the copier still has the wrong address, check the active adapter and DHCP server before changing the queue. If the addresses match but printing still fails, check reachability and the queue or driver.
| Symptom | First check | What the result can tell you |
|---|---|---|
| One computer cannot print | Compare its queue with a working computer | An old queue or port may be local to that computer |
| Nobody can print but the copier is reachable | Compare the queue destination with the copier’s current address | The queue may point at an older address |
| Printing works from the office but fails from guest Wi-Fi | Identify the two networks and their access rules | A firewall boundary may be doing its intended job |
| Several devices lose connections at once | Check whether clients received an address, gateway and DNS settings | The issue may involve DHCP or the wider network |
A copier’s settings page can usually tell you the active address and whether the device uses DHCP. Compare it with the reservation and the print queue. If they disagree, identify which setting should be authoritative. Change one setting at a time and retest from an employee’s computer.
Record the address and what depends on it
Record the equipment name, location, address, assignment method, responsible DHCP service and any software or queue that depends on the address. If equipment moves to another network, verify the gateway and DNS settings as well. Keep the record where the business can find it during a router swap or provider handover.
Choose how to refer to a device
A queue can point directly to an IP address, or use a name if the office’s name resolution supports it. A stable name can simplify replacements, provided someone updates the record and checks what clients resolve. Discovery-based queues can be convenient on a single network, while discovery traffic may not cross a segmented network without deliberate configuration. Record the actual queue destination so the next person knows where to look.
After replacement, test ordinary printing and any workflows that use separate settings, such as secure print release or scanning to a shared folder. Save the queue configuration alongside the address record.