A phone can disconnect from home Wi-Fi overnight and reconnect in the morning with the same local IP address. On another day, it may come back with a different one. Neither result necessarily indicates a fault. On networks that use DHCP, an address is commonly assigned as a lease rather than permanently attached to a device.
DHCP, or Dynamic Host Configuration Protocol, supplies network configuration to clients. The assigned IP address is only one part of that configuration. A client can also receive information such as the subnet mask, default gateway, and DNS server addresses.
A DHCP address has a time limit
A DHCP server maintains a pool of addresses that it can offer to clients. In a typical home network, the router performs this server role for devices on the local network.
When a client obtains an address, the server associates that assignment with a lease duration. The client can use the address under the terms of that lease and normally attempts to renew it before the lease expires. Successful renewal can let the device continue using the same address without any visible interruption.
The time limit helps the server manage a finite address pool. A device that leaves the network does not need to hold an address forever. After an old lease is no longer valid and the server considers the address available, that address can eventually be assigned elsewhere.
A lease duration is a network policy choice, not a universal fixed interval. Home routers, managed networks, and hotspot systems can use different values.
Reconnecting does not always produce a new address
Disconnecting Wi-Fi does not automatically discard every trace of an existing lease. If a client returns while its previous assignment can still be used, it may request that address again. The server can accept the request when the address remains suitable and available.
This is one reason repeated reconnects can appear to give a device a permanent address even though DHCP is active. Stability over several connections is not proof of a static configuration.
The opposite can also happen. A server may decline a requested address, its lease records may have changed, the old address may have been reassigned, or the client may be joining a different logical network. In those cases, the device can receive another address from the available pool.
Router restarts do not guarantee an address change either. Some devices preserve DHCP lease data across restarts, while others may rebuild state differently. The result depends on the server implementation, its saved configuration, and the state of the network.
Local addresses identify interfaces inside a network
The address supplied by a home DHCP server is normally used for communication on the local IP network. It should not be confused with the public address that an internet provider presents toward the wider internet.
Several phones, computers, televisions, and other devices can each have distinct local addresses while their outbound internet traffic passes through a router using address translation. Changing a laptop’s local DHCP address therefore does not imply that the household’s public internet address also changed.
The reverse is also true. An internet provider can change the router’s public address while local DHCP assignments remain exactly as they were.
This distinction matters when diagnosing saved connections. A printer, media server, or other local service may become unreachable at a previously used local address even though ordinary internet access still works.
Reservations add stability without static client settings
Many routers support a DHCP reservation, sometimes described with terms such as address reservation or static lease. A reservation tells the DHCP server to associate a chosen local address with a particular client identity according to the server’s configuration.
The client can still use DHCP. It asks the network for configuration as usual, but the server is set to offer the reserved address when the matching client requests service.
That differs from manually entering a static IP address on the client. With manual configuration, the device itself is told to use specific network settings rather than obtaining them through the normal DHCP exchange.
A reservation can be convenient for a device that other local systems need to reach at a predictable address. It also keeps address allocation under the router’s control. The reserved address still has to fit the local network design and avoid conflicting assignments.
Client identity deserves some care. Modern devices can use randomized hardware addresses on Wi-Fi networks as a privacy feature. Since DHCP servers can use client identifiers or link-layer addresses when tracking assignments, changes in the identity presented to the network can affect how a reservation or previous lease is recognized. Exact behavior depends on the client and server.
An address change is not the same as an address conflict
Receiving a different DHCP address is usually routine. An address conflict is a separate condition in which two interfaces attempt to use the same IP address on the same relevant network segment.
A correctly operating DHCP server manages its own allocation state to reduce that risk, but conflicts can still arise from manual settings, overlapping configuration, multiple uncoordinated DHCP servers, or other network errors.
This is also a reason to avoid choosing an arbitrary manual address merely to keep a device stable. If that address sits inside the server’s dynamic pool and the server has no knowledge of the manual assignment, it may later offer the same address to another client.
A reservation configured on the network equipment is often a cleaner option when a stable local address is required and the router supports it.
The lease explains stability and change
DHCP sits behind a routine behavior that can otherwise look inconsistent: a device often gets the same local address, but it is not guaranteed to keep it indefinitely. The server grants configuration for a period, the client can renew it, and later connections can reuse or replace the assignment depending on network state.
For ordinary browsing, the exact local address usually needs no attention. It becomes relevant when another device depends on reaching a service at a known address, when a reservation is being configured, or when a local connectivity problem is being separated from an internet-side address change.