dynamic IP address
An IP address which changes periodically, when each time a user connects to their internet service provider.
dynamic IP address: an address that changes with each connection
A dynamic IP address is a temporary numerical address assigned to a device when it connects to a network, typically the internet through an ISP. Unlike a static address that remains fixed indefinitely, a dynamic address is released and reassigned each time the connection ends or after a set lease period expires. The assignment is managed by a DHCP server, which pools available addresses and distributes them to requesting clients on demand.
When you disconnect from your ISP or your lease expires, your assigned address returns to the pool and may be given to another user within hours or days. ISPs use dynamic addressing because the number of active simultaneous connections is typically much smaller than the total number of subscribers. A residential ISP serving 100,000 customers might maintain only 10,000 to 15,000 routable addresses, relying on the fact that not everyone is online at the same time. This creates efficiency in address allocation and reduces the ISP's infrastructure costs.
Practical implications in industrial networks
In industrial settings, dynamic addressing creates complications. Equipment that needs consistent network identity, such as SCADA hosts, PLCs, or remote monitoring systems, cannot reliably use dynamic addresses. A device receiving a new address after reconnection will lose established connections and be invisible to systems expecting it at the old address. This is why production networks typically assign static addresses to critical equipment or use DHCP with address reservations that guarantee a specific device always receives the same IP from the pool.
The term 'dynamic' refers to the allocation method itself, not to the stability of any single connection. During active use, a device's assigned address does not change. The dynamic behavior occurs only at the boundaries, when leases expire or connections terminate. Most home broadband and mobile data connections use dynamic addressing by default; enterprise networks and industrial facilities almost always override this with static assignment or reservation schemes for any device requiring reliable network access.