MyIP.dogAn IP change can be normal
An IP change can happen when a provider assigns a different public address, a device joins another network, a VPN selects another exit or an IPv6 temporary address rotates. These events affect different parts of a connection. Before trying to stop the change, identify which address moved: the local interface value, the router's WAN value or the public source observed by a website.
Start with the public IP checker and record the address family, source and time. Compare that observation with an earlier result collected the same way. An IP change inferred from a different device, browser or network may simply reflect a different path. A changed city label with an unchanged address is a separate geolocation question and should not be treated as address reassignment.
Identify which address changed
A computer's local IPv4 address can change while the household's public exit stays the same. Conversely, the public exit can change while every local device keeps its familiar private value. NAT separates these observations. The public versus private guide explains why the two layers need to be checked independently.
For example, a laptop moving from 192.168.10.20 to 192.168.10.21 on the same LAN has experienced a local IP change. That example alone says nothing about the source an internet service sees. If your problem is an external allowlist, inspect the external observation. If it is a local printer or file share, inspect the device and local assignment instead.
DHCP and assignment
DHCP can provide time-limited address assignments. A client renews its lease, and the server controls which address is offered or retained. A renewal does not require a different value every time. The protocol is described in RFC 2131. Dynamic assignment therefore does not imply that an IP change happens on a fixed daily schedule.
A home router may run a DHCP server for local devices while receiving its own configuration through a separate provider mechanism. Those are different assignments controlled by different parties. When investigating an IP change, identify the relevant server or provider before adjusting lease settings. Changing the router's LAN lease duration does not directly control an ISP's public-address policy.
Why a router restart is not a guarantee
Restarting equipment may reconnect it with the same assignment. It may instead lead to a different address, depending on the provider's policy and the connection state. There is no universal waiting period that guarantees a new value for every service. If you require predictable behavior, ask the provider about the actual service rather than relying on a generic reboot recipe.
Repeated restarts can also make an IP change investigation harder. They interrupt active sessions and add events to the timeline before you understand the original symptom. Record the current state before investigating an IP change. A stable connection with a harmless address rotation calls for a different response from one that repeatedly drops and reconnects during work or calls.
Switching Wi-Fi and cellular
Switching from home Wi-Fi to a mobile network changes the path carrying your traffic. A different public source is expected. The same applies when a laptop joins an office network, uses a phone hotspot or moves to a guest connection. An IP change in these situations does not imply that the device has lost its identity or that the earlier test was incorrect.
Some devices and applications can use different available paths according to their settings. Keep the connection type and active interface in your notes. If a phone uses multiple cellular lines, record which one supplied data. An IP change that appears random can become understandable when it is aligned with a network switch or a reconnection event.
VPN exit selection
A VPN can alter the source seen by an internet service. Reconnecting, selecting another location or using a different server can lead to an IP change at the exit. Split tunneling can also make two applications expose different sources at the same time. A single browser result does not describe every connection on the device.
For a controlled comparison, record the baseline and VPN state before an authorized change, then repeat the same test. Preserve the browser, address family and network where possible. If work policy requires the tunnel, use its support process rather than disconnecting it casually. The useful finding is which path changed, not simply that two screenshots contain different numbers.
Temporary IPv6 addresses
IPv6 can give a device multiple addresses, including temporary ones used for outgoing connections. RFC 8981 describes temporary address generation intended to limit straightforward correlation through a long-lived interface identifier. A changing temporary suffix can therefore be expected behavior. It does not necessarily mean the network's whole prefix changed.
Compare the prefix and the rest of the address separately when investigating an IPv6 IP change. Also remember that expanded and compressed notation can represent the same value. Before counting two differently written strings as two different addresses, normalize them with IP lookup. A spelling difference is not a network reassignment.
Distinguish reassignment from switching protocols
A browser may use IPv4 for one request and IPv6 for another, depending on destination support and connection behavior. Comparing a dotted IPv4 result with a colon-separated IPv6 result does not demonstrate that one assignment replaced the other. Both protocols may be available simultaneously. Use the IPv6 test to observe them separately.
When logging an IP change, include the family and test endpoint or method. That keeps your comparison meaningful. A dual-stack endpoint and an IPv4-only endpoint can legitimately produce different observations. Do not disable IPv6 merely to make two tools match; first establish whether their methods were actually intended to return the same type of result.
When reassignment causes a real problem
An external allowlist tied to one source may stop matching after the observed public address changes. A local bookmark pointing at an old device address may also stop working. Those are concrete symptoms. Record the old and new observations privately, the affected service and the time the failure began, then ask which assignment or access rule should be stable.
For a local service affected by an IP change, a managed DHCP reservation may be appropriate. For a public service, a provider's static assignment or a suitable access architecture may be needed. Dynamic DNS can update a name when an address changes, but it does not by itself remove upstream NAT or open a firewall. Choose a response to the actual IP change rather than broadening access rules unnecessarily.
Keep a useful observation record
Keep a small log with time, address family, observation method, network, VPN or relay state and the symptom. Add deliberate events such as joining Wi-Fi, reconnecting a tunnel or restarting equipment. You do not need continuous public posting of your address history. A few comparable observations around the failure are often more useful than a large collection without context.
If an IP change happens while everything is working, note it before deciding that it needs intervention. If an IP change coincides with repeated interruptions, ask the network operator to investigate the connection events and assignment policy. A public lookup alone cannot inspect the provider's lease history or prove why its infrastructure chose another source.
What a different value does not prove
An IP change is not automatic evidence of hacking, anonymity or a clean reputation. Accounts, cookies and other application state can persist across addresses. A newly observed value may be shared with other users or have its own previous history. Conversely, an unchanged address does not prove that a service is statically assigned forever.
The static versus dynamic guide explains the difference between an observed pattern and a service guarantee. Use that distinction when asking for support or planning remote access. Once you identify the scope and cause of the IP change, you can decide whether to leave normal behavior alone, update the relevant configuration or request a different service arrangement.
For an intentional IP change, use how to change your IP address. Choose a method that matches the public or local value you need to alter, record the baseline, and verify the same address family afterward.
If an IP change breaks a hostname used for an otherwise reachable service, read dynamic DNS. An updater can maintain its address record, while routing, firewall policy and application availability still need their own checks.