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  • What is IP Address (Internet Protocol address)?

IPAM glossary

What is IP Address (Internet Protocol address)?

An IP address (Internet Protocol address) is a numerical identifier that labels a network interface and indicates where it sits on an IP network. It lets routers forward packets to the correct destination, and it comes in two versions, IPv4 with 32 bits and IPv6 with 128 bits.

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An IP address is a numerical identifier that routes packets across networks, with IPv4 using 32 bits and IPv6 using 128 bits, and is essential for modern enterprise networking where tens of thousands of addresses span data centers, cloud networks, and mobile devices. Poor address management causes significant operational outages including duplicate address conflicts, overlapping subnets, and DHCP pool exhaustion, often exacerbated by reliance on manual spreadsheets and undocumented static assignments. Accurate IP address tracking is critical for security incident response, firewall rule enforcement, and compliance with privacy regulations such as GDPR that treat IP addresses as personal data when linked to individuals.

  • IPv4 address exhaustion has driven adoption of private addressing ranges, network address translation, and IPv6’s 128-bit format to support the billions of unique addresses now required across enterprise infrastructure.
  • Duplicate IP configurations cause intermittent connectivity as ARP entries flip between hardware addresses, typically occurring when static addresses are manually configured within DHCP pools without proper exclusions or reservations.
  • Stale or inaccurate IP address records in spreadsheets and outdated IPAM systems weaken incident response capabilities by creating uncertainty about which device held a specific address at a critical moment in time.

IP address at a glance

AttributeValue
Full nameInternet Protocol address
CategoryNetwork addressing identifier
Defined inRFC 791 for IPv4 and RFC 8200 for IPv6
OSI layerLayer 3 (network layer)
Primary useIdentifying interfaces and routing packets between networks
Related termsIPv4, IPv6, subnet, DHCP, IPAM, MAC address, NAT

How IP address works

An IP address has a network portion and a host portion, and routers use the network portion to decide where to send each packet. Assignment can be manual or automatic.

  1. Address assignment: An interface receives an address either from an administrator who configures it by hand (static) or from a server using DHCP (dynamic). IPv6 hosts can also build addresses through stateless autoconfiguration.
  2. Prefix interpretation: A subnet mask or prefix length, such as /24, splits the address into a network part and a host part. A device compares a destination against its own prefix to decide whether the target is local.
  3. Local delivery or forwarding: If the destination is on the same subnet, the device sends the packet directly. Otherwise it sends the packet to its default gateway, which is a router address on the local subnet.
  4. Hop-by-hop routing: Each router matches the destination address against its routing table and passes the packet toward the next hop until it reaches the destination network.

On a local link, the IP address is mapped to a MAC address, using ARP in IPv4 or Neighbor Discovery in IPv6, so the frame can be delivered. The MAC address identifies the hardware interface on one link, while the IP address identifies position in the network and can change. Private ranges, loopback addresses such as 127.0.0.1, and network address translation affect how addresses appear outside a local network.

Why IP address matters in enterprise networks

IPv4 uses 32-bit addresses, which allows about 4.3 billion unique values, and exhaustion of that space drove the use of private addressing, network address translation and IPv6, which uses 128-bit addresses as defined in RFC 8200. Enterprises now track tens of thousands of addresses across data centers, cloud networks, branch offices and mobile devices, often in both protocol versions.

Poor address management causes outages that are hard to diagnose. Two devices configured with the same address produce intermittent connectivity, overlapping subnets break routing and VPN links, and exhausted DHCP pools leave new devices unable to connect. Spreadsheets and undocumented static assignments make these errors more likely as the network grows.

Addresses also matter for security and investigation. Logs, firewall rules and access controls reference IP addresses, so an inaccurate record of which device held an address at a given time weakens incident response. Privacy regulations such as the GDPR can treat IP addresses as personal data when they can be linked to an individual.

IP address vs MAC address

An IP address is a logical address assigned to an interface and used to route packets across networks, while a MAC address is a hardware-level identifier used to deliver frames within a single local network segment.

AttributeIP addressMAC address
LayerNetwork layer (layer 3)Data link layer (layer 2)
ScopeUsed for routing across networksUsed for delivery within one local network segment
Length32 bits in IPv4, 128 bits in IPv648 bits in the common format
AssignmentConfigured manually, assigned by DHCP, or built through autoconfigurationNormally set by the manufacturer, though many operating systems can override it
Changes with locationUsually changes when a device moves to a different subnetStays the same when the device moves, unless randomized or overridden

IP address vs DHCP

A static IP address is one an administrator configures by hand on a device, while DHCP is the protocol that leases addresses to devices automatically from a managed pool. What is DHCP?

AttributeIP addressDHCP
ConfigurationEntered manually on each deviceSupplied by a server on request
Change effortRequires editing each deviceChanged centrally in server scopes
Conflict riskHigher if records are not trackedLower, because the server tracks leases
Typical useServers, routers, printers and other fixed infrastructureLaptops, phones and general client devices

Common IP address issues

Two devices holding the same address cause intermittent connectivity, with sessions dropping as ARP entries flip between hardware addresses. This often happens when someone configures a static address inside a DHCP pool without an exclusion or reservation.

When two sites or a site and a cloud network use the same range, routing and VPN tunnels fail or send traffic to the wrong place. It usually surfaces after a merger or when a new VPC is built without checking existing allocations.

Clients fail to obtain an address and fall back to a self-assigned address in the 169.254.0.0/16 range. Long lease times combined with many transient devices such as guest Wi-Fi are a common cause.

A mask set too long makes a host treat on-link neighbors as remote and send them to the gateway, while one set too short makes it try to reach remote hosts directly. The result is partial connectivity where some hosts respond and others do not.

Spreadsheets or outdated IPAM data list addresses as free that are in use, or the reverse. Engineers then assign live addresses to new devices, or leave reclaimable space unused.

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IP address FAQ

Related terms

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IPAM (IP address management)

A method for planning, tracking, and managing IP address space on a network.

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IPv4 (Internet Protocol version 4)

The fourth version of Internet Protocol that uses 32-bit addresses to route most of today’s internet traffic; the global supply of IPv4 addresses is exhausted. Learn More

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IPv6 (Internet Protocol version 6)

The most recent version of Internet Protocol, which uses 128-bit address space; there are 340 undecillion IPv6 addresses.

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Subnet mask

A 32-bit number that masks an IP address, and divides the IP address into network address and host address.

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DHCP (Dynamic Host Configuration Protocol)

The standard mechanism to dynamically assign IP addresses within a network.

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Dynamic IP Address

An IP address that changes from time to time, unlike a static IP address.

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Static IP address

An IP address that doesn’t change and was manually configured for a device, versus one that was assigned by a DHCP server.

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RFC 1918 networks

Ranges of IP addresses set aside for private use on TCP/IP networks.

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