Public IP Address

Learn how ISPs assign public IP addresses, why IPv4 is exhausted, how CGNAT affects your connection, and what determines the public IP your household receives. Check your current public IP instantly.

How Public IP Addresses Are Assigned

The global IP allocation hierarchy: IANA (Internet Assigned Numbers Authority) manages the global IPv4 address pool. IANA delegates large blocks to five Regional Internet Registries: ARIN (Americas), RIPE NCC (Europe/Middle East), APNIC (Asia-Pacific), LACNIC (Latin America), and AFRINIC (Africa). These RIRs then allocate smaller blocks to ISPs, which assign individual IPs to their customers. Your public IP traces back through this hierarchy — every IP block has a registered owner documented in WHOIS databases.
IPv4 exhaustion — a solved problem with lasting consequences: IANA distributed its last unallocated IPv4 blocks in February 2011. APNIC and RIPE NCC ran out of their standard allocations by 2011 and 2012. ARIN exhausted its free pool in 2015. IPv4 addresses are now only available on the secondary market, where organizations sell unused allocations — prices have reached $40–60 per address. This scarcity drives CGNAT deployment and slows IPv4-based internet expansion.
IPv4 secondary markets and why adoption of IPv6 remains slow: Despite IPv4 exhaustion, IPv6 adoption has been gradual because NAT allowed ISPs to extend IPv4's reach indefinitely. IPv6 deployment requires simultaneous upgrades across ISPs, CDNs, enterprise networks, and home equipment. The operational complexity and cost of dual-stack management, combined with NAT's effectiveness as a stopgap, has meant that IPv6 penetration is still incomplete in many markets even decades after IPv6 was standardized.
What determines your specific public IP: Your public IP is determined by your ISP's network infrastructure, the city you are in, and whether your ISP uses CGNAT. Large ISPs manage separate IP pools for different regions — customers in the same city share IP blocks registered to that region. Your ISP's DHCP server assigns you an IP from the appropriate pool when your router connects. Business plans with static IPs assign a permanently reserved IP from a different pool.
How often dynamic IPs change: DHCP leases determine how long your ISP holds an IP assignment for your connection. Residential lease durations are typically 24 hours to 7 days. When a lease expires, the DHCP server may renew the same IP or assign a different one from the pool — the outcome depends on pool pressure (how many IPs are in demand at that time). Restarting your router almost always triggers an IP change because the old lease is released before renewal.

Check My IP

How to Identify Your Public IP Assignment

Check your current public IP: Load this page to see the IP your ISP has currently assigned to your connection. This is the address that appears in server logs, firewall whitelists, and geolocation databases for any traffic originating from your home network.
Identify your IP's registered owner via the ISP field: The ISP/organization field shows who registered the IP block containing your address. This is your ISP for most residential connections, or a data center company if you are behind a VPN or proxy.
Detect CGNAT by checking your router's WAN IP: Access your router's admin interface (typically 192.168.1.1) and note the WAN/Internet IP. If it falls within 100.64.0.0 to 100.127.255.255 (RFC 6598 CGNAT range) or any other RFC 1918 range, your ISP is using CGNAT and you do not have a dedicated public IP — the IP shown in this tool is shared with other subscribers.
Confirm static vs. dynamic assignment: Record your current public IP and check again after restarting your router and after 24–48 hours without restarting. If the IP changes, your assignment is dynamic. If it is consistently the same, contact your ISP to confirm whether it is a formally provisioned static IP or simply a long-duration DHCP lease.
Look up your IP block's history: ARIN, RIPE, and APNIC WHOIS databases let you search any IP to see its allocation history, current registrant, and contact information. This is how network engineers verify IP block ownership and trace abuse reports.

Real-World Use Case

A software developer wants to run a Minecraft server from their home and share it with friends. They configure the server, set up port forwarding on port 25565, and share what they believe is their public IP. Friends cannot connect. The developer checks this tool and notices the IP it shows (203.0.113.18) is different from the WAN IP displayed in their router admin panel (100.64.42.7). The WAN IP starting with 100.64 is a telltale sign of CGNAT — confirming the ISP has not given them a dedicated public IP. The developer calls their ISP and learns that CGNAT is used by default on their residential plan, but a static public IP is available for an additional monthly charge. After upgrading, the router receives a true public IP, port forwarding works, and friends can connect directly to the Minecraft server. Understanding the public IP assignment structure — specifically that CGNAT prevents port forwarding — transformed a confusing connectivity problem into a one-call ISP fix.

Best Practices

Understand your ISP's IP assignment policy before configuring self-hosted services: Call or check your ISP's documentation to find out whether they use CGNAT, offer static IPs, and what the typical DHCP lease duration is — this knowledge prevents hours of misdiagnosed troubleshooting.
Factor in IPv4 market pricing if building internet infrastructure: If you are building services that require dedicated IPv4 addresses (e.g., email servers, hosting platforms), budget for IPv4 costs — purchasing or leasing IPv4 addresses on the secondary market can cost $40–60 per address, plus annual maintenance fees from the RIRs.
Deploy IPv6 alongside IPv4 on all new infrastructure: IPv6 is the long-term solution to address exhaustion. All modern operating systems, cloud providers, and major ISPs support IPv6. Enabling it on new servers and networks future-proofs your infrastructure and reduces reliance on increasingly expensive IPv4 addresses.
Use cloud-based relay servers if CGNAT prevents direct inbound connections: Services like Cloudflare Tunnel, ngrok, or self-hosted WireGuard on a cloud VM allow you to receive inbound traffic through a cloud server with a dedicated public IP — bypassing CGNAT entirely without needing a static IP from your ISP.
Periodically audit your public IP range using WHOIS: If your business uses dedicated IP ranges, check WHOIS periodically to confirm registration details are current — outdated WHOIS records can cause email deliverability issues and abuse report delays.

Performance & Limits

IPv4 address pool size: The total IPv4 address space is 2^32 = 4,294,967,296 addresses. After subtracting reserved ranges (private RFC 1918, multicast, loopback, documentation, and link-local), the usable public IPv4 pool is approximately 3.7 billion addresses — all of which are now allocated at the RIR level.
DHCP lease renewal behavior: Most residential ISP DHCP servers use a lease renewal process where the router contacts the server at 50% of lease duration to extend the current IP. If renewal succeeds, the same IP is retained. Only if renewal fails (e.g., due to reconnection or lease expiry without renewal) does the router receive a potentially different IP from the pool.
CGNAT scale: A single CGNAT gateway can serve thousands of residential subscribers behind one public IP using port address translation (PAT). The CGNAT device tracks individual sessions by combining the subscriber's private IP, port, and the public IP/port it translates to.
ISP IP block sizes: ISPs receive IP allocations in CIDR blocks from their RIR — common allocations range from /22 (1,024 IPs) for small ISPs to /8 (16 million IPs) for the largest global carriers. Your IP falls somewhere within your ISP's allocated range.
Secondary market transfer timeline: When an organization sells its IPv4 block, the RIR must approve and record the transfer. The process takes days to weeks, during which geolocation databases may not reflect the new registrant — causing temporary geolocation inaccuracies for the transferred block.

Common Mistakes to Avoid

Assuming a dedicated public IP means a static IP: A dedicated public IP (not CGNAT) and a static IP are different things. A dedicated dynamic IP is yours alone but changes on DHCP lease renewal. A static IP is a dedicated IP that never changes. Confirm with your ISP which type you have — both are better than CGNAT, but only static guarantees permanence.
Overlooking IPv4 exhaustion as a cause of CGNAT: ISPs deploy CGNAT not by choice but because they have exhausted their IPv4 allocations and cannot obtain more without purchasing on the secondary market. Understanding that CGNAT is a structural consequence of IPv4 scarcity helps frame ISP conversations — you may need to pay for a static IP allocation specifically reserved for you.
Expecting port forwarding to work without verifying CGNAT status first: Every self-hosting guide assumes you have a direct public IP. Before following any port forwarding tutorial, confirm your public IP situation using this tool and compare it to your router's WAN IP — if they differ, CGNAT is the culprit and port forwarding setup is premature.
Conflating IPv6 deployment with IPv4 exhaustion being solved: IPv6 solves the address exhaustion problem for new deployments, but it does not restore the IPv4 pool. IPv4 and IPv6 are separate address spaces that coexist — most internet traffic still uses IPv4, and IPv4 addresses will remain scarce and expensive indefinitely regardless of IPv6 adoption.

Privacy & Security

Your public IP block reveals your ISP and general region: Every public IP belongs to a registered block with a documented owner — typically your ISP. Anyone with your IP can query WHOIS and identify your ISP and the region where the block is deployed. This is by design; IP routing depends on this registry data.
ISP DHCP logs create a traceable history: Your ISP logs every IP assignment with timestamps and account identifiers. This creates a permanent record linking your account to every public IP you have ever been assigned — retention periods vary but are often 6 months to 2 years, governed by local telecommunications regulations.
IPv4 scarcity drives secondary market transparency: IPv4 transactions above a certain size must be approved and recorded by RIRs, making large IP holdings publicly documented. This transparency is deliberate — it prevents hoarding and makes IP ownership disputes resolvable through registry records.
No data retained by this tool: This page reads and displays your public IP for informational purposes only. No requests are logged, no IPs are stored, and the tool does not require any account or personal information.

Frequently Asked Questions

Who assigns IP addresses and how does the system work?

IP address assignment follows a strict hierarchical system. At the top, IANA (Internet Assigned Numbers Authority, operated by ICANN) manages the global IP address pool and policy. IANA delegates large blocks (historically /8 blocks of ~16 million addresses) to five Regional Internet Registries: ARIN (North America), RIPE NCC (Europe, Middle East, Central Asia), APNIC (Asia-Pacific), LACNIC (Latin America and Caribbean), and AFRINIC (Africa). Each RIR allocates smaller blocks to National Internet Registries (NIRs) and directly to Internet Service Providers (ISPs). ISPs then assign individual IP addresses or small ranges to their customers using DHCP for dynamic assignment or manual configuration for static IPs. The entire system is documented in WHOIS databases maintained by each RIR.

How many public IPv4 addresses exist and are they really exhausted?

The IPv4 address space contains exactly 4,294,967,296 addresses (2^32). After reserving blocks for private networks (RFC 1918), loopback, multicast, documentation, and link-local use, approximately 3.7 billion addresses are usable as public IPs. At the RIR level, yes — they are exhausted. IANA gave away its last unallocated /8 blocks in February 2011. All five RIRs have since depleted their free pools. New IPv4 addresses are now only available through secondary market transfers between organizations, at market prices of $40–60 per address. However, due to NAT and CGNAT, the same public IP can serve many users simultaneously, which is why the internet continues to function despite exhaustion.

Why is IPv6 not more widely used despite IPv4 exhaustion?

IPv6 adoption has been slow due to several interconnected factors. First, NAT provided a workable stopgap — a single IPv4 address can serve hundreds of devices, postponing the urgency. Second, IPv6 deployment requires simultaneous upgrades across ISPs, CDNs, enterprise firewalls, and end-user equipment — the coordination overhead is significant. Third, IPv4 and IPv6 are incompatible at the network layer, requiring dual-stack infrastructure during the transition period, which increases operational complexity and cost. Fourth, many legacy applications and systems were written with IPv4 assumptions and require updates to support IPv6. Despite these barriers, IPv6 adoption has been increasing — major CDNs, cloud providers, and mobile carriers have strong IPv6 support, and IPv6 traffic continues to grow as a percentage of global internet traffic.

What is IPv4 exhaustion and how does it affect my connection?

IPv4 exhaustion means that no new IPv4 addresses can be obtained through the standard RIR allocation process — the free pool is gone. For your connection, the most direct consequence is CGNAT: because ISPs cannot get new IPv4 addresses to assign individually to each customer, many residential ISPs now use CGNAT to share one public IP among multiple households. This affects you if you try to host services at home (port forwarding breaks), run a VPN server at home (inbound connections fail), or need a consistent IP for security whitelisting (CGNAT IPs can be shared with many other users). If exhaustion had not occurred, every household could have received a dedicated public IP — instead, CGNAT and IPv6 became the structural workarounds.